Pleistocene Palaeoecology of the Eastern Darling Downs · Darling Downs, southeastern Queensland, Australia, were examined in detail to establish an accurate, dated palaeoecological

SCHOOL OF NATURAL RESOURCE SCIENCE

QUEENSLAND UNIVERSITY OF TECHNOLOGY

Pleistocene Palaeoecology of the Eastern Darling Downs

by

Gilbert J. Price

BAppSc (Hons) Ecology

2006

Queensland University of Technology

Supervisors

Gregory E. Webb

Bernard N. Cooke

Submitted in fulfillment of the requirements for the degree

Doctor of Philosophy

“From the Condamine River, the country rises very gently, almost

imperceptibly, till the road passes between two hills of ranges, when the

basaltic rock re-appears again. Very extensive shallow valleys or plains,

generally with a creek, overgrown with reeds, covered with rich high grass,

were spread before my eyes, when I had passed these hills, the right of

which goes under the name of Rubieslaw, and the left under that of Sugar-

loaf... All this country, from the Condamine to the range, is called the

DARLING DOWNS. There is no equal to them all over the colony...”

Ludwig Leichhardt, 23 June, 1843.

Leichhardt, W.F.L. 1843. Journal (28/12/1842 - 24/07/1843). Handwritten

manuscripts in the Mitchell Library, Sydney.

ABSTRACT

Several late Pleistocene fossil localities in the Kings Creek catchment,

Darling Downs, southeastern Queensland, Australia, were examined in detail

to establish an accurate, dated palaeoecological record for the region, and to

test human versus climate change megafauna extinction hypotheses.

Accelerator Mass Spectrometry (AMS 14C) and U/Th dating confirm that the

deposits are late Pleistocene in age, but the dates obtained from the two

methods are not in agreement. Fluvial depositional accumulation processes

in the catchment reflect both high-energy channel and low-energy episodic

overbank deposition. The most striking taphonomic observations for

vertebrates in the deposits include: 1) low representation of post-cranial

elements; 2) high degree of bone breakage; 3) variable abrasion but most

identifiable bone elements with low to moderate degree of abrasion; 4) low

rates of bone weathering; 5) low degree of carnivore bone modification; and

6) low degree of articulated or associated specimens. Collectively, those

data suggest that the material was transported into the deposit from the

surrounding proximal floodplain and that the assemblages reflect hydraulic

sorting. A multifaceted palaeoecological investigation revealed significant

habitat change between superposed assemblages of site QML796. The

basal fossiliferous unit contained species that indicate the presence of a

mosaic of habitats including riparian vegetation, vine thickets, scrubland,

open and closed woodlands, and open grasslands during the late

Pleistocene. Those woody and scrubby habitats contracted over the period

of deposition so that by the time of deposition of the youngest horizon, the

creek sampled a more open type environment. Sequential faunal horizons

show a step-wise decrease in taxonomic diversity that cannot be explained

by sampling or taphonomic bias. The decreasing diversity includes loss of

some, but not all, megafauna and is consistent with a progressive local loss

of megafauna in the catchment over an extended interval of time.

Collectively, those data are consistent with a climatic cause of megafauna

extinction, and no specific evidence was found to support human

involvement in the local extinctions. Better dating of the deposits is critically

important, as a secure chronology would have significant implications

regarding the continent-wide extinction of the Australian megafauna.

KEY WORDS: fluvial sedimentology, taphonomy, megafauna

extinction, climate change, Pleistocene, Darling Downs, Australia.

LIST OF PUBLICATIONS / SUBMITTED MANUSCRIPTS

PRICE, G.J. 2002. Perameles sobbei sp. nov. (Marsupialia, Peramelidae), a

Pleistocene bandicoot from the Darling Downs, south-eastern

Queensland. Memoirs of the Queensland Museum. 48: 193-197.

PRICE, G.J. 2005 (2004)a. Fossil bandicoots (Marsupialia, Peramelidae) and

environmental change during the Pleistocene on the Darling Downs,

southeastern Queensland, Australia. Journal of Systematic Palaeontology.

2: 347-356.

PRICE, G.J. 2005b. Pleistocene megafauna extinction: new evidence from the

Darling Downs, southeastern Queensland. Quaternary Australasia. 23(1):

15-16.

PRICE, G.J. & HOCKNULL, S.A. 2005. A small adult Palorchestes (Marsupialia,

Palorchestidae) from the Pleistocene of the Darling Downs, southeast

Queensland. Memoirs of the Queensland Museum. 51: 202.

PRICE, G.J., TYLER, M.J. & COOKE, B.N. 2005. Pleistocene frogs from the

Darling Downs, southeastern Queensland, Australia, and their

palaeonenvironmental significance. Alcheringa. 29: 171-182.

PRICE, G.J. & SOBBE, I.H. 2005. Pleistocene palaeoecology and

environmental change on the Darling Downs, southeastern Queensland,

Australia. Memoirs of the Queensland Museum. 51: 171-201.

PRICE, G.J. & WEBB, G.E. revised. Late Pleistocene sedimentology,

taphonomy and megafauna extinction on the Darling Downs, southeastern

Queensland, Australia. Australian Journal of Earth Sciences.

PRICE, G.J. submitted. Late Pleistocene ecosystem dynamics, habitat

change, and species extinction on the Darling Downs, southeastern

Queensland, Australia. Palaeogeography, Palaeoclimatology,

Palaeoecology.

CONTENTS

STATEMENT OF ORIGINAL AUTHORSHIP 13

ACKNOWLEDGEMENTS 14

INTRODUCTION 16

DESCRIPTION OF RESEARCH PROBLEM 16

OBJECTIVES OF STUDY 18

SPECIFIC AIMS OF STUDY 18

RESEARCH PROGRESSION 19

LITERATURE REVIEW 23

INTRODUCTION 23

PLEISTOCENE 25

MEGAFAUNAL EXTINCTION 27

Anthropogenic models of extinction 28

Blitzkrieg 28

Sitzkrieg 32

Hyperdisease 36

Climate models of extinction 37

Co-evolutionary disequilibrium model 38

Mosaic-nutrient model 39

Multicausal or ecological models of extinction 41

Keystone herbivore model 41

Self-organised instability 43

Chronologies 44

DARLING DOWNS 51

Geographical and geological settings 51

Palaeoecology 53

Kings Creek Catchment 54

Site QML796 55

Excavation 56

Stratigraphy, sedimentology and taphonomy 57

Palaeoecology 60

Dating 63

Correlation to other Kings Creek deposits 65

SUMMARY 65

PUBLISHED PAPERS / SUBMITTED MANUSCRIPTS 67

Paper 1. PRICE, G.J. 2005 (2004)a. Fossil bandicoots (Marsupialia,

Peramelidae) and environmental change during the Pleistocene on the

Darling Downs, southeastern Queensland, Australia. Journal of Systematic

Palaeontology. 2: 347-356 67

INTRODUCTION 69

GEOGRAPHY AND STRATIGRAPHY 69

MATERIALS AND METHODS 69

SYSTEMATIC PALAEONTOLOGY 70

DISCUSSION 74

ACKNOWLEDGEMENTS 76

REFERENCES 76

Paper 2. PRICE, G.J., TYLER, M.J. & COOKE, B.N. 2005. Pleistocene frogs from

the Darling Downs, southeastern Queensland, Australia, and their

palaeonenvironmental significance. Alcheringa. 29: 171-182 79

GEOGRAPHICAL AND GEOLOGICAL SETTINGS 82

MATERIALS AND METHODS 82


DISCUSSION 86

ACKNOWLEDGEMENTS 89

REFERENCES 89

Paper 3. PRICE, G.J. & SOBBE, I.H. 2005. Pleistocene palaeoecology and


Australia. Memoirs of the Queensland Museum. 51: 171-201 93

SETTING 95

METHODS 96

Sedimentology 96

Taphonomy 96

Fauna 97

Dating 98

RESULTS 98

Sedimentology 98

Taphonomy 99


Ecological remarks 111

Molluscs 111

Amphibians 112

Reptiles 112

Marsupials 113

Rodents 114

DATING 114

DISCUSSION 114

Sedimentology 114

Taphonomic history of bones 115

Palaeoenvironmental interpretation 116

CONCLUSIONS 118

ACKNOWLEDGEMENTS 119

LITERATURE CITED 119

Paper 4. PRICE, G.J. & WEBB, G.E. in press. Late Pleistocene sedimentology,


Queensland, Australia. Australian Journal of Earth Sciences 125

ABSTRACT 127

INTRODUCTION 127

SETTING 132

METHODS 133

Excavation and sedimentology 133

Taphonomic analysis 134

Faunal attributes 139

RESULTS 139

Sedimentology and stratigraphy 139

Interpretation 146

Stratigraphic correlation with Kings Creek 149

Bivalve taphonomy 150

Interpretation 150

Vertebrate taphonomy 151

Bone appearance 151

Faunal attributes 153

Skeletal part representation 158

Skeletal breakage 160

Carnivore modification 164

Abrasion and hydraulic sorting 165

Articulated and associated material 167

Taphonomic interpretation 169

Biases relating to faunal groups 170

Mortality profiles 174

Carnivore modification 175

Accumulation processes 176

DISCUSSION 178

CONCLUSION 180


REFERENCES 182

Paper 5. PRICE, G.J. submitted. Late Pleistocene ecosystem dynamics,

habitat change, and species extinction on the Darling Downs, southeastern


Palaeoecology 191

ABSTRACT 192

INTRODUCTION 193

DARLING DOWNS DEPOSITS 196

METHODS 198

Sampling procedure 198

Ecological analogies to modern habitats 198

Diversity estimates 201

Dating 203

RESULTS 205

Species 205

Ecological dynamics 211

Feeding adaptations 211

Locomotory adaptations 213

Life habits 214

Diversity 215

Dating the deposits 216

DISCUSSION 219

Palaeoecology 219

Habitat change 223

Dating and implications 228

CONCLUSIONS 232


REFERENCES 233

GENERAL DISCUSSION 243

SIGNIFICANCE OF STUDY 243

MEGAFAUNA EXTINCTION HYPOTHESES 246

Anthropogenic models 246

Blitzkreig / Overkill 246

Sitzkrieg 247

Hyperdisease 248

Climate models of extinction 249

Co-evolutionary disequilibrium model 249

Mosaic-nutrient model 250

Multicausal or ecological models of extinction 251

Keystone herbivore model 251

Self-organised instability 252

FUTURE DIRECTIONS 252

SUMMARY 255

CONCLUSIONS 257

REFERENCES 259

APPENDICES 307

Appendix 1. PRICE, G.J. 2002. Perameles sobbei sp. nov. (Marsupialia,

Peramelidae), a Pleistocene bandicoot from the Darling Downs, south-

eastern Queensland. Memoirs of the Queensland Museum. 48:

193-197 307


Remarks 310

Affinities 310


LITERATURE CITED 312

Appendix 2. PRICE, G.J. & HOCKNULL, S.A. 2005. A small adult Palorchestes

(Marsupialia, Palorchestidae) from the Pleistocene of the Darling Downs,

southeast Queensland. Memoirs of the Queensland Museum. 51: 202 313

Appendix 3. PRICE, G.J. 2005b. Pleistocene megafauna extinction: new

evidence from the Darling Downs, southeastern Queensland. Quaternary

Australasia. 23(1): 15-16 315

STATEMENT OF ORIGINAL AUTHORSHIP

The work contained in this thesis has not been previously submitted for a

degree or diploma at any other higher education institution. To the best of my

knowledge and belief, the thesis contains no material previously published or

written by another person except where due reference has been made.

Signature:

Date:

13

ACKNOWLEDGEMENTS

First and foremost, my supervisor, Gregg Webb, must be thanked for his

encouragement and guidance throughout the course of my PhD. Although

Gregg's primary expertise lies in the world of fossil coral reefs, Gregg quickly

developed a love and passion for fossilised rodent jaws, and his input into

my project was paramount to its eventual completion.

Prior to my commencement at university, most of my formal training in

palaeontology was through watching reruns of ‘The Flintstones’ on television.

In time, Bernard Cooke took me on as an Honours student, and eventually

became co-supervisor of my PhD project. His dedication has played a major

role in my transformation from a raw ecology student, to palaeontologist.

Ian, Diane and Amy Sobbe are thanked for their support and generosity

throughout the course of this research. They opened their home, hearts and

refrigerator to me for which I will be forever grateful. Ian was always available

to dig fossils, discuss the latest happenings in palaeontology, and consume

the occasional beverage whenever the time called for it.

Scott Hocknull worked alongside me for the course of my PhD. His

enthusiasm, guidance, and helpful discussions over the occasional lunchtime

basketball game was of great value during the course of this research.

Jian-xin Zhao and Yue-xin Feng provided expertise relating to U/Th

dating, conducted U/Th dating analyses, and produced very exciting results.

Gary and Neville Ronfelt, Peter Dutaillis, and especially, Ian Sobbe and

Trevor Sutton are thanked for allowing free access to properties where fossil

deposits are located.

Alex Baynes, Walter Boles, Brendan Brooke, Trevor Clifford, Alex ‘Gut

Contents’ Cook, Mary Dettmann, Liz Reed, John Stanisic, Mike Tyler, and

Ian Williamson are thanked for assistance and/or critical discussions on

various aspects of Darling Downs palaeoenvironments. Additionally, Alex

Baynes, Henk Godthelp, Russ Graham, Dirk Megirian, Troy Myers, Liz Reed,

Ian Reid, Steve Wroe and several anonymous reviewers provided

constructive comments that greatly improved the quality of the published

manuscripts that came from this work.

14

Assistance in the preparation of fossil material, access to specimens

and/or resources was due to the assistance of Andrew Amey, Ricky Bell,

Phillip Colquhon, Alex ‘they call him Dr. Worm’ Cook, Loc Duong, Peter Jell,

Graham Jordan, Paul Hamilton, Scott Hocknull, Debra Lewis, Owen McCaw,

Matthew Ng, Susan Parfrey, all School of Natural Resource Sciences

administration staff, Luke Shipton, the Sobbe family, Kristen Spring, Paul

Tierney, Greg Todd, Doug and Margaret Turner, Stuart Watt and Warwick

State High School, Joanne Wilkinson, and 100’s of volunteers who gave

freely of their time.

Finally, Desmond and Jennifer Price are thanked for their love and

support over my whole life, particularly during the course of my university

studies.

AMS 14C dating by ANSTO was supported by AINSE Grants 02/013 and

03/123. U/Th dating by ACQUIRE (University of Queensland) was supported

by Australian Research Council Linkage Grant LP0453664. This research

was funded in part by both the Queensland University of Technology and the

Queensland Museum.

15

INTRODUCTION

DESCRIPTION OF RESEARCH PROBLEM

Debate concerning the extinction of the Australian Pleistocene megafauna

has become polarised in recent years. Causes for extinction have been

debated widely with climate change, human hunting and/or human induced

habitat change, or a combination of those factors being the dominant

hypotheses (for recent reviews see Horton, 2000; Barnosky et al., 2004b;

Wroe et al., 2004; Burney & Flannery, 2005). The lack of a spatially

constrained chronology for the extinction of individual species and for human

occupation renders many hypotheses almost impossible to test. Additional

deposits incorporating more complex and detailed ecological analyses and

dating at different regional scales are required to resolve issues relating to

megafauna extinction (O’Connell & Allen, 2004).

The Darling Downs, southeastern Queensland, Australia, is emerging as

an area of major significance in the understanding of late Pleistocene (i.e.,

post-penultimate glacial maximum) megafaunal extinction. It is one of the

most fossiliferous regions in Australia, with over 50 individual Pleistocene

megafauna-bearing fossil localities known in a small (16 000 km2)

geographic area (Molnar & Kurz, 1997). Perhaps most importantly, some of

the youngest known megafaunal remains in Ausrtalia have been recovered

from fluvial deposits in the region (Roberts et al., 2001a).

Despite the apparent significance of the Darling Downs Pleistocene

deposits and associated faunas, few studies have addressed specifically: 1)

aspects of dating; 2) stratigraphy; 3) sedimentology; 4) taphonomy; and 5)

palaeoecology. Other than two optical stimulated luminescence (OSL) dates

presented by Roberts et al. (2001a), there has been little analytical dating

attempted for other megafauna-bearing deposits in the region. Hence,

Darling Downs megafaunal chronologies are largely unknown. Gill (1978)

dated the Talgai hominid skull deposit (Dalrymple Creek, Darling Downs)

using radiocarbon methods and suggested that the deposit was late

Pleistocene. However, megafaunal remains were not recorded in the deposit,

16

and it is unknown whether humans and megafauna overlapped temporally

on the Pleistocene Darling Downs.

Stratigraphic and relative temporal relationships of most deposits in the

region are also poorly known. Previous stratigraphic nomenclature erected

for specific units (see Macintosh, 1967; Gill, 1978) is now considered to be

invalid (Baird, 1986; Molnar & Kurz, 1997). As stratigraphic, sedimentologic

and chronologic details of the deposits are unknown, the deposits of the

region cannot be correlated to each other with any degree of certainty.

Hence, precise stratigraphical, sedimentological and chronological

relationships between Darling Downs deposits and other Australian fossil

deposits remain unclear.

Taphonomic aspects of Darling Downs deposits also have been rarely

documented. Molnar et al. (1999) described general aspects of a deposit

(site QML783, “Ned’s Gully”) that contained articulated remains of

megafauna, but recognised that articulated fossils are rare in the region.

Hence, potential taphonomic biases of most other deposits are unknown,

and thus, provide another factor that limits the precision of all subsequent

palaeoecological interpretations and comparisons.

Pleistocene vertebrate faunas of the region appear to be extremely

diverse. Species lists are dominated by megafaunal taxa, such as

Diprotodon sp., Protemnodon sp., and Macropus titan (e.g., Molnar & Kurz,

1997). Pleistocene habitat reconstructions based on such taxa have led to

interpretations of expansive grasslands and woodlands (Bartholomai, 1976b;

Molnar & Kurz, 1997). However, past collecting in the region focused on the

recovery of large-sized taxa, with smaller forms being overlooked (Molnar

and Kurz, 1997). Small-sized species are more highly valued than large-

sized species in palaeoecological studies as they commonly yield more

precise resolution of habitat and climate data (Brothwell & Jones 1978;

Andrews 1990; Vigne & Valladas 1996). Therefore, previous Darling Downs

palaeoenvironmental interpretations are limited, because the smaller forms

are poorly known.

Darling Downs Pleistocene fossil deposits are particularly important as the

faunas may encompass the late Pleistocene extinction episode in eastern

Australia. Hence, studies of its local faunas, that combine dating, lithofacies,

17

depositional environment, taphonomic, and palaeoecologic analyses, may

help to elucidate causes for megafauna decline and extinction at local,

regional, and potentially continental scales.

OBJECTIVES OF STUDY

The primary objective of this study was to gain a better understanding of the

palaeoecology of the Pleistocene Darling Downs so as to allow the testing of

hypotheses relating to the extinction of the Australian megafauna. Crucial

aspects involved the documentation of depositional environments. Such

investigations incorporated aspects of stratigraphy, sedimentology,

taphonomy, and radiometric age dating. Additionally, palaeoecological

analyses focused on both large- and small-sized taxa that occur in the

deposits and built on the work of Bartholomai (1976b) and Molnar & Kurz

(1997). While Pleistocene fossil deposits are common throughout the entire

Darling Downs, the project was focused on deposits in the Kings Creek

catchment, southern Darling Downs. The Kings Creek catchment is well

constrained in terms of size and contain some of the most abundant and

fossiliferous deposits in the region. It is an ideally suited study area for

investigations of the Pleistocene environment of the eastern Darling Downs.

SPECIFIC AIMS OF STUDY

A project with such broad goals had several specific aims:

1) To standardise collecting practices in order to minimise bias in the

sampling of fossil material, i.e., to design and implement a method of

collecting that targeted both large and small-sized taxa equally.

2) To identify all recognisable fossil material recovered and place it within

specific taxonomic groupings. That analysis formed the basis for all

subsequent biostratigraphical comparisons and palaeoecological

interpretations.

3) To document lithostratigraphic relationships between fossil deposits in the

region. That involved stratigraphic analyses of several fossil deposits as well

as limited radiometric dating.

18

4) To examine potential sources of taphonomic bias within the fossil deposits

in the catchment, thus allowing faunal assemblages to be correlated and

compared with each other with relative degrees of confidence.

5) To gain greater control on palaeoecological aspects of the deposits. In

conjunction with lithfacies and taphonomic analyses, a multifaceted

approach that incorporated ecological analogues to modern species and

communities, and diversity indices, provided detailed information about

palaeoenvironments.

6) To accurately date the deposits. Dating was an important aspect of the

study. Dating assisted in providing a chronology of deposition, and that led to

the establishment of temporal chronologies for species. Dating, combined

with the stratigraphic investigation, helped reveal temporal relationships

between fossil deposits within the catchment, and allowed the deposits to be

correlated at regional and continental scales. Dating also supported

phylogenetic studies of taxa in the deposits.

RESEARCH PROGRESSION

This thesis was constructed so as to provide a clear and coherent guide to

the research progression and follows ‘thesis by publication’ guidelines set by

the Queensland University of Technology (QUT). The literature review

provides the setting for the research by detailing the current up-to-date view

on Pleistocene megafaunal extinctions. The review discusses megafaunal

extinctions in general, but with a focus on the Australian situation. The

extended review continues with the current state of knowledge of Darling

Downs fossil deposits and the methodology employed in the project. The

literature review, of necessity, replicated some literature cited in subsequent

chapters.

Five major papers are presented as individual chapters. The first major

paper (Paper 1) deals with fluvial sampling aspects of the Pleistocene Kings

Creek catchment and palaeoecological aspects of bandicoots recovered

from its deposits. Documentation of the geographic area sampled in

19

palaeoecological studies of fossil vertebrate deposits is rarely attempted,

primarily because it is difficult or impossible to determine the precise

geographical extent represented by samples. The geographical extent of

palaeodrainages is commonly poorly constrained, hence, fossil deposits in

fluvial settings may contain geographically mixed assemblages that include

both local faunas and material transported from varying distances. However,

in this paper, the geography of the modern Kings Creek catchment was used

as a constraint on the potential Pleistocene catchment size. Secondly, early

collecting during initial stages of this project recovered several taxa

previously unknown to have a fossil record in the Pleistocene Darling Downs.

Among those taxa were new records of extant bandicoots and a previously

undescribed fossil bandicoot species (see Appendix 1: Price, 2002).

Palaeoenvironmental interpretations were based on analogy using extant

bandicoots, and hypotheses regarding late Pleistocene habitats and climates

are presented. The palaeoenvironmental interpretations are strengthened

because the size of the geographic area being sampled is well constrained.

Following on from the first paper, the second major paper (Paper 2)

discusses palaeoevnvironmental aspects of the Darling Downs based on

fossil frog assemblages. Small-sized taxa such as frogs and bandicoots are

ideal environmental indicators. Like most small-sized taxa, frogs and

bandicoots generally have small home ranges, specific habitat requirements,

and short life spans. Those ecological and biological traits make them more

useful for habitat reconstructions than many larger-sized taxa. Additionally,

frogs have permeable skins, and multiple life stages, and their value as

environmental bio-indicators is well known. Hence, detailed information

regarding Darling Downs palaeohabitats and climates was gleaned from

examination of fossil frog assemblages. Taphonomic biases are also

identified in this paper, and hypotheses relating to sampling and/or

ecological traits are proposed to explain such biases.

The third major paper (Paper 3) constitutes a significant site study of a

Kings Creek fossil deposit, site QML1396. It represents the first of my

broader excavations of the dated faunas, including the descriptions of over

40 taxa. This paper complements the results of the previous two papers by

presenting a palaeoenvironental interpretation based on the complete fauna

20

from a single fossil deposit. The stratigraphic and sedimentologic

investigative component documented the precise depositional setting of the

site. The taphonomic component of the study builds on the results of paper 2

above, and several biases were revealed in relation to both sampling by the

Pleistocene creek, and possible ecological factors. A palaeoecological

investigation of the deposit revealed significant information about late

Pleistocene Kings Creek habitats. Importantly, the paper provides the first

palaeoecological interpretations from this study that bear on megafaunal

extinction. The paper provides a baseline for comparison with deposits

discussed in subsequent chapters.

The fourth major paper (Paper 4) comprehensively investigates aspects of

stratigraphy, sedimentology and taphonomy of another major deposit in the

Kings Creek catchment, site QML796. Depositional environments are

precisely documented and potential taphonomic biases assessed. Climatic

indicators from the sediments are also discussed. It builds on the results of

paper 3 and allows sites QML796 and QML1396 to be litho- and

biostratigraphically correlated to each other. That is an important aspect of

the study as it allows future studies to examine species changes in the

catchment at different spatial scales. The investigation also allowed

additional development of hypotheses relating to Darling Downs megafaunal

extinction.

The fifth major paper (Paper 5) complements the QML796 site study of

paper 4, and provides a comprehensive interpretation of Pleistocene

palaeoenvironments, both at a single locality, and in a wider catchment

perspective (for additional aspects of fauna, see also Appendices 1 & 2:

Price, 2002 and Price & Hockull, 2005). It details the significant

documentation of late Pleistocene habitat change, ecosystem dynamics and

species extinctions on the Darling Downs. An extensive dating analysis

complements the palaeoenvironmental component and allows the site to be

correlated to independently derived records of Pleistocene climate change.

Hypotheses to explain late Pleistocene habitat and faunal changes support

those derived from investigations of papers 3 and 4. The results have

several important implications relating to the continental extinction of

Australian Pleistocene megafauna.

21

The final section provides an overarching discussion of the significance of

the findings, problems encountered, and future directions of the work.

The reference section includes all literary resources used in the thesis

including those in the published or submitted manuscripts. References used

specifically in the research papers accompany their respective manuscripts

for completeness.

The appendix section contains additional published manuscripts that

came from the work, but did not contribute to the main thrust of the thesis.

22

LITERATURE REVIEW

INTRODUCTION

There have been a growing number of scientific predictions of rapid and

catastrophic climate change occurring in the near future (Bengtsson et al.,

1996; Kappelle et al., 1999, Källen et al., 2001; Kershaw et al., 2003;

Phoenix & Lee, 2004). Significant numbers of such studies have indicated at

least a partial anthropogenic cause for climate change (Houghton et al.,

1996; Gordon et al., 2005; Root et al., 2005). Humans are directly altering

atmospheric composition through gas emissions and disrupting water

balance of large areas of the Earth’s surface through agriculture and other

land degradation activities, and thus, are affecting the cycling of carbon

through many of the planet’s ecosystems (Stern, 2002; Gordon et al., 2005).

Desire to predict possible future climate change has spawned an enormous

amount of literature (Bengtsson et al., 1996; Kappelle et al., 1999; Zachos et

al., 2001; Doorman & Woodin, 2002; Phoenix & Lee, 2004). Many studies

have focused not only on how to prevent or reduce the effects of predicted

climate change (Wigley, 1991; Kappelle et al., 1999; Scheffer et al., 2001),

but they also have attempted to produce predictive models of global warming

and its subsequent effects on biodiversity (Price & Rind, 1994; Zwiers &

Kharin, 1998; Boer et al., 2000; Rosenzweig, 2001; Western, 2001;

Callaghan et al., 2004; Phoenix & Lee, 2004; �ekercio�lu et al., 2004).

Biodiversity is increasingly used as a conceptual focus for the formulation

of conservation policies and practice, primarily in response to the strongest

themes underpinning the founding work on biological diversity: species

extinction and habitat loss. Our understanding of current threats to

biodiversity and the prospects for survival of extant species is informed by

palaeoecology, and in particular, knowledge of previous extinction events.

Mass extinction events have occurred throughout geological time. The Late

Ordovician, Late Devonian, terminal Permian, terminal Triassic and terminal

Cretaceous extinction events saw the loss of between 24-50% of all families

known at those times (Sharpton & Ward, 1990). Hypotheses developed to

explain such events suggest that the impact of extraterrestrial objects or

intense explosive volcanic activity may have adversely affected the climate of

23

those times, thus contributing to the catastrophic extinction rates (Sharpton &

Ward, 1990). However, one of the most important, but less understood

periods of species and habitat loss occurred more recently, during the

Pleistocene.

The emergence of modern floras and faunas on which humans depend for

food and shelter took place during the late Tertiary, finally being

accomplished by the late Quaternary. Most living terrestrial species evolved

at that time and many show adaptations to Quaternary environments.

Tertiary-Quaternary environmental changes on temporal scales on the order

of one hundred thousand years led to speciation within several groups. Many

species evolved fixed adaptations to specialised environments, while others

evolved more generalist adaptations that enabled them to inhabit broad

habitat niches (Lister, 2004). Environments that imposed strong selective

regimes were important in forcing adaptive changes in many species.

Subsequent migrational and evolutionary responses of taxa to fluctuating

Quaternary climatic cycles was a synergistic process (Lister, 2004). The

Quaternary was a time of evolution and subsequent extinction of some of the

largest land reptiles, birds and mammals that the world has ever known.

Colloquially known as the ‘megafauna’ (animals > 44 kg), those animals

included giant lizards, kangaroos and wombats in Australia, huge flightless

moas in New Zealand, and giant ground sloths, mammoths and mastodons

in the Americas. Hypotheses concerning the extinction of those spectacular

creatures during the late Quaternary have been the subject of contentious

and heated debate (e.g., Flannery, 1990 versus Wright et al., 1990; Flannery

1994, 1998 versus Benson & Redpath, 1997, 1998; Gillespie & David, 2001

and Roberts et al., 2001a, b, c, versus Field & Fullagar, 2001 and Wroe &

Field, 2001a, b; Grayson & Meltzer, 2003, 2004 versus Fiedel & Haynes,

2004; Burney & Flannery, 2005; 2006, versus Wroe et al., 2006). The recent

megafaunal extinction differs from all other known mass extinction events

because man has been suggested as the causative agent. Anthropogenic

factors have been clearly implicated in megafauna extinctions in some

regions (e.g., New Zealand; Worthy & Holdaway, 2002), but the role of man

remains unclear in regions such as the Americas and Australia. The paucity

24

of well-dated late Pleistocene megafaunal deposits makes it difficult to test

such extinction hypotheses.

Although Pleistocene deposits containing megafaunal remains are

common throughout Australia (Archer, 1984), few are as diverse and well

represented as those of the Darling Downs, southern Queensland. Over 50

megafauna-bearing deposits have been recorded in the region (Molnar &

Kurz, 1997), including some of the youngest deposits known in Australia

(Roberts et al., 2001a). Despite the significance of the deposits, little work

has been directed towards understanding palaeoecological aspects of the

region. Hence, the research presented here is aimed at better understanding

the Pleistocene faunas of the Darling Downs, their responses to

environmental changes, and their subsequent extinction.

Today, we are in an interglacial period and face similar climatic cycling

regimes to those patterns of climate change evidenced in the Pleistocene

geological record (Berger & Loutre, 2002). At this time of widespread

apprehension over human impacts, it is helpful to consider the history and

effects of past environment fluctuations (Burney & Flannery, 2005). To

understand life as we know it, it is essential to know its history; and to

conserve biodiversity into the future, it is essential to learn lessons from the

past. Knowledge of prehistoric biodiversity may provide insights into the

causes of extinction and the vulnerability of different types of species.

Importantly, such information may help highlight what the danger signs are,

i.e., aspects crucial for the development of strategies for conservation. It is

essential to know if the risks faced by species and ecosystems today are the

same as those faced by species in the past. Studies of Pleistocene climate

fluctuations and species extinction may have predictive value for assessing

the effect of climate change on extant species.

PLEISTOCENE

Relative to the past 65 million years of Tertiary geological history, the speed

and amplitude of global temperature oscillations during the Quaternary were

unprecedented (Zachos et al., 2001). The climate of the Quaternary was

dominated by repetitive glacial and interglacial cycles, i.e., ice ages. From

25

2.7 million years (Ma) to 800 thousand years ago (ka), such cycles were

dominated by 41 ka oscillations, and since 800 ka, by 100 ka oscillations

(Ashkenazy & Tziperman, 2004). Such transitions from glacial to interglacial

periods and variability were driven by orbital forcing (i.e., variations in the

Earth’s eccentricity, axial tilt, and precession; Milankovitch, 1941; Paillard,

2001). In the oceans, sea level fluctuated markedly, periodically encroaching

and retreating across coastal plains (Lambeck & Chappell, 2001).

Continental glaciers and ice sheets developed in the Northern Hemisphere

and contracted or expanded in response to the cyclicity of glacial and

interglacial periods (Hubberten et al., 2004). In regions of the Southern

Hemisphere where glaciers were not as significant (such as Australia;

Barrows et al., 2002), extensive arid zones developed in response to the

cool, dry and windy glacial periods (Bowler, 1986; Hesse et al., 2004).

Quaternary climate oscillations led to dramatic shifts in vegetation structure

in most regions of the world. Vegetation changed in structure and

composition as dictated by both climate and the differential response of

individual floral taxa to climate (Webb et al., 2003; Shuman et al., 2004). In

many regions, vegetation responded quickly (within ~100 years) when

climate changed rapidly on centennial scales (Webb et al., 2003). In the

Northern Hemisphere, changes from open steppe and herb tundra to open

shrub tundra were commonly associated with shifts towards cooler

conditions (Andreev et al., 2002, Lacourse et al., 2005). In the Southern

Hemisphere, interglacials were dominated by woodlands, whereas glacials

were dominated by open scrub and grasslands (Hope et al., 2004). Thus,

progressive changes toward more open conditions were more likely to occur

during glacial cycles.

Some of the most dramatic shifts in vegetation have been documented in

deposits generally younger than 50 ka, such as in Australia (Johnson et al.,

1999; Turney et al., 2001b; 2004; Field et al., 2002), Eurasia (Andreev et al.,

2002; Hubberten et al., 2004) and America (Webb et al., 2003; Shuman et

al., 2004). Those changes may have been responses to naturally driven

climatic variables such as increases in the severity and cycling of El Nino

Southern Oscillation (Turney et al., 2004). However, the precise effects of

naturally driven climate change as a causative agent of late Pleistocene

26

vegetation changes may be obscured by an additional confounding factor-

the global expansion of modern humans, Homo sapians.

MEGAFAUNAL EXTINCTION

Late Pleistocene climatic instability coincided with the global extinction of

almost 100 genera of large-sized terrestrial vertebrates (Barnosky et al.,

2004b). Such extinctions were most dramatic in the Americas and Australian

regions where 72-88% of all megafaunal taxa were lost (Barnosky et al.,

2004b). However, extinctions were moderate in Africa, Europe and Asia,

where only 18-36% of megafaunal genera became extinct (Barnosky et al.,

2004b). It is commonly suggested that the long history of human predation

on megafaunal species in such areas created selective pressures for prey

wariness and defensive behaviour (Fiedel & Haynes, 2004), and that may

explain the lower extinction rates. However, thus far there is no universally

accepted hypothesis to explain Pleistocene global megafaunal extinctions,

particularly in areas such as Australia and the Americas.

The debate over the causes of the extinctions have become particularly

polarised in recent years, with several hypotheses being suggested. The

most popular are those that suggest either: 1) an anthropogenic component

to the extinctions, via overhunting, or indirect habitat or ecosystem

modifications (Martin, 1984; Diamond, 1989b; Flannery, 1990; 1994; 1999a;

MacPhee & Marx, 1997; Miller et al., 1999; 2005a; Alroy, 2001, Brook &

Bowman, 2004; Diniz-Filho, 2004; Fiedel & Haynes, 2004; Johnson &

Prideaux, 2004; Lyons et al., 2004a; Prideaux, 2004, Wroe et al., 2004;

Burney & Flannery, 2005; Johnson, 2005a, b; Lowry, 2005; Steadman et al.,

2005; Surovell et al., 2005); 2) naturally driven climatic changes (Graham &

Lundelius, 1984; Guthrie, 1984, 2003; Ficcarelli et al., 1997; Grayson &

Meltzer, 2003; Kuzmin & Orlova, 2004; Shapiro et al., 2004; Stuart et al.,

2004), or 3) a combination of both (Calaby, 1976; Owen-Smith, 1987, 1988;

Murray, 1991; Frison, 1998; Field & Dodson, 1999; Forster, 2003; Barnosky

et al., 2004b; McNeil et al., 2005; Trueman et al., 2005; Wroe, 2005;

Boeskorov, 2006; Bulte et al., 2006).

27

Anthropogenic models of extinction

On islands such as New Zealand, humans have caused extinctions through

multiple synergistic effects involving overhunting and indirect habitat

modification (Anderson, 1989; Worthy & Holdaway, 2002). However,

megafaunal kill sites and other direct evidence of human induced habitat

modification has yet to be demonstrated on the continents where Pleistocene

extinctions were most dramatic, i.e., Australia and America (Flannery, 1990;

Grayson, 1991; 2001; Grayson & Meltzer, 2003). Hypotheses of

anthropogenic-induced megafaunal extinction include: 1) blitzkrieg (rapid

over-hunting); 2) sitzkrieg (fire, habitat alteration); and 3) hyperdisease

hypotheses.

Blitzkrieg

The global blitzkrieg hypothesis explains differential rates of megafaunal

extinctions between the world’s land masses during the late Quaternary

(Martin, 1963; 1984). The hypothesis centres around five main observations

(Wroe et al., 2004). 1) Megafaunal extinction rates were highest on

landmasses where humans colonised within the last 60 000 years (Roberts

et al., 2001; Fiedel & Haynes, 2004; Lyons et al., 2004a; Burney & Flannery,

2005; Surovell et al., 2005). 2) Species on remote islands (e.g., Polynesia,

West India) have proven to be vulnerable to human hunting (Worthy &

Holdaway, 2002; Steadman et al., 2002, 2005). 3) Ethnographic data

suggest that humans preferentially hunt large-sized species (Duncan et al.,

2002). 4) Late Quaternary extinctions were more significant in large-bodied

taxa than small-sized taxa (Johnson, 2002; Brook & Bowman, 2004;

Johnson & Prideaux, 2004). 5) Climatic fluctuations during the Quaternary,

prior to the last glacial maximum and human colonisation, did not result in

significant megafaunal extinction (Martin, 1984; Flannery, 1990; 1994;

Moriarty et al., 2000; Barnosky et al., 2004a; Lyons et al., 2004a). Blitzkrieg

extinction events are considered to have occurred if extinction takes less

than 500 years (Barnosky et al., 2004b), whereas more generalised overkill

is considered to have occurred in 1 500 years or more (Whittington & Dyke,

1984). The basic blitzkrieg hypothesis suggests that a combination of

selective hunting and prey naiveté produced significant extinctions wherever

28

humans colonised new land masses during the late Quaternary (Martin,

1984). A more attritional overkill hypothesis of megafuana extinction was

proposed for Australia by Prideaux (2004). Prideaux (2004) suggested that

megafauna attrition over a long duration (e.g., 20 000 years) was driven by

an elevation of human-based hunting pressures following initial human

colonisation. A combination of small population sizes and low reproduction

rates of megafaunal species may have rendered megafauna taxa

susceptible to increased predation pressures (Murray, 1991; Johnson, 2002;

2005b; Prideaux, 2004).

However, there is little direct evidence of human interaction with

megafaunal species. Sites documenting human butchery of megafaunal

species are particularly rare (Grayson & Meltzer, 2003; Wroe et al., 2004). Of

more than 70 late Quaternary archaeological sites in America, less than 20

document the human processing of megafaunal taxa (Grayson & Meltzer,

2002; Surovell et al., 2005). Additionally, those kill or butchery sites are

restricted only to large-sized proboscidians (i.e., mammoths and mastodons).

Demonstrable kill sites for other common late Quaternary megafaunal

species such as camels, horses and sloths are completely lacking in North

America (Grayson & Meltzer, 2003) and are rare in South America (Nami,

1996; Alberdi et al., 2001). Therefore, because the more common

megafauna are rarely associated with the butchery sites, those data are not

entirely consitent with blitzkrieg extinction (Grayson & Meltzer, 2003).

Similarly, few sites show evidence of an association between humans and

megafaunal species in Australia. Cuddie Springs, northern New South

Wales, shows a direct, in situ association between humans and megafaunal

species (Dodson et al., 1993; Field & Dodson, 1999; Trueman et al., 2005).

However, human processing marks recorded on fossil bone from the deposit

are related to an extant species of kangaroo, not extinct megafaunal taxa

(Field & Dodson, 1999). Rarity of kill sites in America and Australia has been

used as evidence to support the blitzkrieg extinction model (Martin, 1984;

Flannery, 1990). That is, because of the rapidity of a blitzkrieg-type

extinction, kill sites are unlikely to be found (Fiedel & Haynes, 2004).

However, such arguments render the hypothesis very difficult to test. Ideally,

29

direct evidence of flagrant prey overuse is essential to sustain the blitzkrieg

hypothesis (Prideaux, 2004).

In the Americas, the presence of big-game hunting tools (e.g., stone spear

points) in the fossil record is commonly cited as supporting overkill models of

extinction (Martin, 1984). Thus, if such technology is lacking in other areas, it

may lend support to non-overkill mechanisms of megafauna extinction (Wroe

et al., 2004). In Australia, stone spear points are not known until the mid-

Holocene (Flood, 1995). An absence of specialised hunting technologies

does not preclude the hunting of megafauna, but rather, suggests that

optimum prey size and hunting efficiency is reduced (Wroe et al., 2004).

However, most Australian megafauna species weighed less than 100 kg,

markedly smaller than their ‘big-game’ counterparts of the Americas (Murray,

1991). Ethnographic data suggests that in Australia, humans hunted animals

as large as red kangaroos (46 kg, mean sex weight; Strahan, 1995) and

crocodiles (327 kg, mean sex weight; Webb & Manolis, 1989) with

unsophisticated hunting tools such as clubs and wooden spears (Mulvaney &

Kamminga, 1999). Thus, anthropogenic predation on the majority of

Australian Pleistocene megafauna was possible by hunters with relatively

unsophisticated hunting technologies. Additionally, if big-game hunting tools

for taxa as large as Diprotodon (2 700 kg; Wroe et al., 2003a) ever existed, it

may be unlikely that such technologies would have been retained for tens of

millennia (i.e., into the Holocene) after they were last useful (Prideaux,

2004). In Australia, there is evidence of the manufacture of more efficient

stone tools from late Pleistocene to the Holocene. On a parallel, there is also

an increase in the efficiency of plant processing technology (e.g., seed

grinding) since the late Pleistocene (Fullager & Field, 1997). Without

specialised plant processing technology, societies were likely more

dependent on meat than advanced societies that could exploit a range of

plant resources (Wroe et al., 2004). An absence of specialised plant

processing technologies may have acted as a constraint on both human

population sizes, and their ability to disperse. However, the affect of plant

processing technology on Australian megafauna-human interaction is largely

unknown. For the American situation, Bulte et al. (2006) supported overkill

models, and suggested that the role of anthropogenic agriculture was

30

minimal in relation to megafauna extinction. Alternatively, they suggested

that humans attained high population densities by exploiting small-sized prey

taxa during and after megafaunal extinctions (Bulte et al., 2006). Small-sized

taxa may have been an important alternative food resource during and after

the period that megafaunal prey populations were extirpated.

Simulations developed to model overkill extinction hypotheses commonly

result in contradictions, favouring either rapid human-induced overkill (e.g.,

Alroy, 2001a, b; Diniz-Filho, 2004), rapid initial overkill followed by extinction

due to later stresses (Brook & Bowman, 2004), overkill with assistance from

climate (Bulte et al., 2006), natural climate changes (e.g., Choquenot &

Bowman, 1998), or they are inconclusive (e.g., Beck, 1996; Brook &

Bowman, 2002). One of the most comprehensive, but controversial, models

was the Alroy (2001a, b) simulation. Alroy (2001a, b) focused on the initial

entry of Clovis hunters into North America and correctly predicted the fate of

34 of 41 species. The mean time to extinction was 895 years, thus

supporting overkill, but not blitzkrieg senso stricto. However, the model failed

to account for the low number of kill sites in North America, and then over-

predicted the effect of hunting by not allowing prey to lose naiveté to humans

as their populations increased. As in most other simulations, assumptions of

complete prey naiveté generally result in models that support overkill (Brook

& Bowman, 2002). Despite the shortcomings of the Alroy (2001a, b)

simulation, the model has the potential to be further developed by

incorporating assumptions of geographic ranges, carrying capacity, and

human and prey dispersal (Barnosky et al., 2004b). However, in general, the

uncertain nature of human and megafauna interactions is a significant

impediment in developing realistic models of extinction. Additionally, most

computer simulations of human influences use data based on relatively

sophisticated modern day hunter-gathers as direct proxies for the behaviour

of Pleistocene societies. However, the assumption that Pleistocene human

behaviour is analogous to modern societies is undemonstrated and

therefore, limits the value of computer modelling (Wroe et al., 2006; Wroe et

al., in press). Another major assumption of algorithm-based models is that all

extinct taxa were present at the time of human arrival. However, in Australia

at least, chronologies demonstrating a temporal overlap between most

31

megafaunal taxa and humans are patchy at best. Although algorithm-based

models can integrate existing data to investigate various scenarios of

megafauna extinction, the output relies on many explicit and implicit

unconstrained assumptions.

Generally, the strength of the blitzkrieg and attritional predation

hypotheses are limited by a lack of reliable chronologies of initial human

colonisation and megafaunal extinction. The geographic distributions of

humans and other megafauna through time are very poorly constrained.

Overkill hypotheses rely on specific, but unproven chronologies of human

occupation and megafaunal extinctions. Thus, testing overkill hypotheses

requires more examples of megafauna co-occurring with humans in well-

stratified, unambiguously dated sites across the continents (Horton, 1984;

Prideaux, 2004). Head (1995) noted that unambiguously dated sites

containing evidence of human occupation that are too old, or megafauna that

are too young, “can blow it (some anthropogenic extinction hypotheses)

apart”. In Australia, recent chronologies and geochemical analyses reported

for the Cuddie Springs archaeological deposit (northern New South Wales),

have demonstrated a temporal overlap of humans and megafauna on the

Australian continent for a minimum of 15 000 years (Trueman et al., 2005).

Thus, the long temporal overlap between humans and megafauna

automatically refutes blitzkrieg, but not attritional, overkill extinction

hypotheses for Australian megafauna. Additional details regarding the

Cuddie Springs deposit are discussed below.

Sitzkrieg

Unequivocal impacts of human-induced habitat change on islands, such as

Madagascar, New Zealand, and Hawaii, have been cited as a potent

argument that prehistoric humans also caused extinctions on the continents

(Diamond, 1989a). Such island extinctions commonly occurred rapidly after

human arrival (James et al., 1986; Flannery, 1994; Steadman et al., 1999;

Burney et al., 2003; 2004). Initial human colonisation on islands such as New

Zealand was followed by massive environmental change. Those

environmental changes were the result of a combination of factors that

included the introduction of rats and dogs, fire-driven deforestation, and

32

vertebrate extinction. It is well documented and accepted that direct over-

hunting caused the extinction of the moa in New Zealand (Anderson, 1989;

Diamond, 1989a; Worthy & Holdaway, 2002). However, several smaller-

sized species were also lost due to subsequent habitat destruction, or

through direct predation or competition effects from taxa that arrived with

humans (Diamond, 1989b). Colloquially, such indirect anthropogenically-

related extinction events are known as ‘sitzkrieg’ extinctions (Diamond,

1989b; Barnosky et al., 2004b).

Island species are particularly vulnerable to sitzkrieg extinction events due

to the high level of endemism of their faunas. Island species may have small

population sizes and be confined to well-delineated areas of land that may

undergo rapid environmental change (Grayson, 2001; Grayson & Meltzer,

2002). Additionally, taxa that occur on islands that lack mammalian predators

commonly lose predator escape responses (Roff, 1994; Duncan &

Blackburn, 2004), and that may make them susceptible to extinction

following mammalian colonisation. However, the impact of sitzkrieg-related

factors on faunas of the continents is questionable, primarily because of the

greater range of refuges in such large landmasses. However, Fiedel and

Haynes (2004) recognised continents simply as gigantic islands and

suggested that while endemic taxa could escape anthropogenic related

pressures for a period of time, they could not escape indefinitely.

In Australia, the introduction of the dingo (Canis lupus dingo) by humans

3.5 ka (Gollan, 1984) has been implicated in the mainland extinction of the

thylacine (Thylacinus cynocephalus), Tasmanian devil (Sarcophilus harrisii),

and Tasmanian native hen (Gallinula morterii) (Johnson & Wroe, 2003).

Over-competition between the dingo with the thylacine and devil (Archer,

1974; Corbett, 1995) and over-predation of the native hen possibly led to

mainland extinctions of those taxa. However, the only clear evidence linking

the disappearance of those mainland species is the timing of the arrival of

the dingo. Other factors such as increases in the human population,

innovations in hunting technologies and more intensive use of resources,

and mid-Holocene climate changes may also have been contributing factors

to their extinction (Johnson & Wroe, 2003). With regards to Australian

Pleistocene megafauna extinctions, it is unknown if humans actively

33

introduced previously non-native species. Although several small-sized, non-

volant taxa entered Australia throughout the Pleistocene via natural

landbridges (Flannery, 1995; Winter, 1997), such species were unlikely to

have been introduced by humans.

On continental scales, the use of fire in the landscape by early human

colonisers has become a complex and contentious issue. Very few studies

have linked archaeological and palaeoecological data to determine the role

of anthropogenic fire in the landscape (Bowman, 1998). In Australia, the

function and role of aboriginal burning of modern landscapes has been well

documented (Jones, 1969; Nicholson, 1981; Kohen, 1995; Bowman, 1998;

Gott, 2005). The ‘fire-stick farming’ model developed to explain late

Pleistocene extinctions (Jones, 1969) suggests that early Aborigines

changed the frequency and nature of fires in order to manipulate animal and

plant resources. The effect of increased firing was to produce great changes

in the vegetation, essentially simplifying vegetation communities downwards

along the spectrum from mature forest to immature grassland (Horton, 1982;

Lowry, 2005). Long-term effects of fire include the reduction of dense

woodland forests and the expansion of savannah grasslands. Aboriginal

burning was probably important for developing and maintaining habitat

mosaics that favoured small-sized species (Johnston et al., 1989; Flannery,

1990; 1994; Bowman, 1998), and was probably detrimental for the survival of

megafaunal taxa, the majority of which depended on woodlands (Horton,

1980; 1982). Thus far, fire-related extinction has only been specifically

suggested for one species of Australian megafauna, the giant dromornithid

bird Genyornis newtoni, in central Australia (Miller et al., 1999; 2005a). Miller

et al. (1999; 2005a) investigated diets of Genyornis and extant emus,

Dromaius novaehollandiae, in the Lake Eyre region over the last 140 000

years. Miller et al. (1999; 2005a) suggested that dietary changes in Dromaius

and localised extinction of Genyornis at ~50-45 ka was the result of massive

habitat changes. They argued that climatic forcing of habitat changes at ~50-

45 ka was unlikely because the previous climatic shifts associated with the

penultimate glacial maximum (i.e., ~140 ka) did not result in such massive

ecosystem reorganisation (Miller et al., 2005a). Thus, Miller et al. (1999;

2005a) suggested that a changed fire regime driven by initial human

34

colonisers prompted the habitat changes, and ultimately, resulted in

Genyornis extinction. Genyornis was a specialised feeder and was unable to

adapt to the changing environment, whilst Dromaius had more generalised

feeding strategies and was able to survive the extinction event (Miller et al.,

2005a). However, evidence linking anthropogenic burning and Genyornis

extinction is ambiguous (Bowman, 2002; Wroe et al., 2004; Johnson,

2005a). Although chronologies presented by Miller et al. (1999; 2005a) may

correspond to initial human colonisation of the Australian continent, there is

no evidence of human occupation in the Lake Eyre region at ~50-45 ka.

Additionally, a paucity of charcoal in the fossil deposits does not support

significant firing of the landscape, either natural or anthropogenic.

Alternatively, a growing body of evidence is beginning to demonstrate that

shifts towards glacial biomes and major climatic instability occurred Australia-

wide around 50 ka (Bowler et al., 2003; Barnosky et al., 2004b; Hope et al.,

2004), and that may be associated with habitat change and species

extinction in the Lake Eyre region at that time.

More broadly, Johnson et al. (1999) and Miller et al. (2005b) suggested

burning and disruption of vegetation cover as a cause for modification of the

Australian Summer Monsoon (ASM) during the late Pleistocene. The

penetration of the ASM into the interior of the continent is dependent on the

transfer of moisture from the biosphere to the atmosphere. Thus, changes to

the vegetation type brought on by anthropogenic burning possibly reduced

the wet season feedback and diminished the effectiveness of the summer

monsoon (Johnson et al., 1999). Such a change may be implicated in the

extinction of the Australian megafauna. However, the role of humans in ASM

modification has been strongly contested (Horton, 2000; Bowman, 2002).

There are several gaps in the knowledge of the origins of the ASM, and that

lack of knowledge is associated with difficulties in differentiating potential

anthropogenic impacts from natural inherent variability (Bowman, 2002).

In the Australasian region, abrupt changes of charcoal concentrations in

late Quaternary pollen cores, such as those at Lake George (Singh &

Geissler, 1985), Lynch’s Crater (Kershaw, 1986; Turney et al., 2001b),

Lombok Ridge (Wang et al., 1998), Lake Eyre and Lake Frome (Luly, 2001),

indicate sudden increases in the incidence of fires. Such increases in fire

35

regimes commonly have been attributed to the role of human fire use in the

landscape (Bowman, 1998; Wang et al., 1998; Luly, 2001, Turney et al.,

2001). However, the relationship between increases in burning and

anthropogenic factors has been questioned, primarily because there is no

other direct evidence of humans in the landscape at those times (see Clark,

1983; Wright, 1986; Head, 1989; Bowman, 2002). Instead, the relationship

between humans and increases of charcoal concentrations has been linked

merely on the basis of dated chronologies between the age of the deposits

and supposed human colonisation (Bowman, 1998; 2002). Development of

accurate chronologies of initial human colonisation is extremely problematic,

and is discussed further below.

Hyperdisease

The hyperdisease hypothesis attributes Pleistocene megafaunal extinctions

to virulent diseases inadvertently brought in by newly arrived humans or

species that accompanied them (e.g., dogs; MacPhee & Marx, 1997; Fiedel,

2005). Smaller-sized taxa may have greater resilience to disease than large-

sized taxa as they have differing life history traits (e.g. shorter gestation time,

greater population sizes, etc.). Hence, Pleistocene disease-related extinction

events would have been biased towards larger-sized species (MacPhee &

Marx, 1997; Fiedel, 2005). For a disease to have the potential to result in

significant extinctions, several criteria must be met: 1) the pathogen must

have a stable carrier in a reservoir species; 2) the pathogen must have a

high infection rate; 3) the pathogen must cause a high mortality rate (circa

50-75%); and 4) the pathogen must have multiple hosts without causing a

threat to humans (Lyons et al., 2004b). With the exception of rabies, few

known viruses may fit such criteria (Lyons et al., 2004b). Even so, rabies has

a low incidence of infection (MacPhee & Marx, 1997).

Lyons et al. (2004b) attempted to model the affect of the West Nile virus

(recently introduced to North America) on bird species of different sizes and

taxonomic orders, and compared that to observed variables of Pleistocene

extinctions. They also demonstrated that it is more likely that hyperdisease

would target species of all sizes, a prediction in contradiction with the

observed patterns of Pleistocene extinctions (Lyons et al., 2004b). Hence,

36

even if a disease does meet all of the criteria of a hyperdisease (i.e., Lyons

et al., 2004b) it may not result in size-biased global extinction events such as

those of the late Pleistocene (Miller et al., 2005a).

Climate models of extinction

One of the major factors that has lent support to the overkill model of

extinction is that glacial-interglacial cycles have been operating for much of

the Pleistocene, yet most extinctions seem to be clustered near the time of

the latest Pleistocene glacial maximum, which is more or less coincident with

the introduction of humans in some areas (e.g., North America, Grayson &

Meltzer, 2002; Australia, O’Connell & Allen, 2004). However, in several

regions, particularly Australia, long-term records from coastal lakes and

pollen cores suggest that although aridification was an ongoing process

through the late Pleistocene, different glacial maxima were associated with

different degrees of aridity (Longmore & Heijnis, 1999; Hope et al., 2004,

Stevenson & Hope, 2005). Significantly, the last glacial maximum was the

most severe of those recorded and was followed by very dry conditions in the

Holocene (Nanson et al., 1992; Longmore & Heijnis, 1999; Lambeck et al.,

2002; Hope et al., 2004). If those results are correct, it provides a rational

explanation for why extinctions might be concentrated around the last glacial

maximum. The last glacial maximum may have been uniquely severe in

terms of aridity. The arrival of humans may be coincidental, but there is no

longer a requirement for an external (i.e., human) agency in the extinctions.

A major difficulty in postulating climatic change as the causal agent of

megafauna extinction has been determining exactly what effect such a

change would have had on individual faunas. Late Pleistocene climatically

driven vegetation changes occurred globally (Whitehead, 1981; Leyden,

1984; Barnosky, 1985; Jackson & Weng, 1999; Longmore & Heijnis, 1999;

Dupont et al., 2000; Andreev et al., 2002; Field et al., 2002; Webb et al.,

2003; Hope et al., 2004; Hubberten et al., 2004), but the direct effect on

particular faunas remains unclear (Johnson & Prideaux, 2004). In many

regions, the relationship between megafaunal extinction and vegetation

change is unclear because of a lack of reliable dates (Barnosky et al.,

37

2004b). Two main climatically related extinction hypotheses have been

proposed, the co-evolutionary disequilibrium, and mosaic nutrient models.

Co-evolutionary disequilibrium model

Coevolution refers to the common evolution of multiple taxa that share close

ecological relationships, with selective forces making evolution of a particular

taxon at least partially dependent on another (Graham & Lundelius, 1984). In

coevolved communities, a balance is established for the biota involved in the

interaction. Environmental change, such as that observed in late Pleistocene

communities, may cause dramatic biotic reorganisation resulting in

disequilibrium. The consequences of coevoutionary disequilibrium may vary

from the establishment of a new equilibrium or to the extinction of one or

more of the species involved. Late Pleistocene environmental effects may

have disrupted coevolutionary equilibrium, and thus reduced niche

differentiation of megaherbivores and increased competition between

species. Coevolutionary disequlibrium is not restricted to particular

taxonomic groups, size or ecological categories, and has been used to

explain the differential extinction or survival of herbivores during the

Pleistocene (Graham & Lundelius, 1984).

Two competing models for how communities might react to such

environmental changes were developed by Clements (1904; 1916) and

Gleason (1926). The Clementsian model suggests that large groups of

species in equilibrium are determined by biological interactions (primarily

competition) and move dependently as integrated communities (Clements,

1916). The Gleasonian model suggests that species respond to

environmental change individualistically, in accordance with individual

tolerance limits (Gleason, 1926). Therefore, communities are continually

emergent features (Graham et al., 1996; Cannon, 2004). Hence, non-

analogue assemblages (i.e., fossil assemblages of modern taxa whose

extant populations are allopatric; Lundelius, 1983; 1989) may be formed by

species responding in a Gleasonian manner to environmental changes.

Graham et al. (1996) conclusively demonstrated that, for North American

mammals at least, species do respond individualistically to environmental

changes (i.e., in a Gleasonian manner), although other factors including

38

biological interactions and stochastic events may also play a role.

Gleasonian-type responses may drive evolutionary change at sub-

continental spatial and temporal scales, with Clementsian-type responses

operating at smaller temporal and geographic scales (Barnosky, 2001).

Mosaic-nutrient model

The mosaic-nutrient model of late Pleistocene extinction events suggests

that climatic changes in seasonal regimes decreased plant diversity and

spatially increased zonation. Such changes resulted in: 1) a shorter, less

diverse growing season; 2) decreases in the quality and quantity of

resources; and 3) development of more homogeneous habitats (Lundelius,

1983, 1989; Guthrie, 1984; Stafford et al., 1999). Those changes were likely

to have resulted in decreasing community diversity, range contractions,

lowering of body masses, and commonly, extinction (Guthrie, 1984).

The mosaic-nutrient extinction hypothesis is difficult to test in several

regions. In areas such as Australia, the late Pleistocene fossil record of

large-sized taxa is poorly known, and their chronologies are poor owing to a

lack of reliable dates. Hence, the precise geographic ranges of megafaunal

taxa during the Pleistocene are poorly known. In North America, the fossil

record is better documented. The average distances of late Pleistocene

geographic range shifts of mammal species were on the order of 1 200 - 1

400 km, and they appear to have been similar during the pre-glacial to

glacial, glacial to Holocene and Holocene to recent intervals (Lyons, 2003).

Such periods were characterised by climatically driven vegetational changes

(Webb et al., 2003) and coincided with increased seasonality. Hence, the

mosaic-nutrient extinction hypothesis may at least partially explain late

Pleistocene megafaunal extinction in North America.

Factors relating to the lowering of body masses of late Pleistocene taxa

are also difficult to assess. Relict late Pleistocene populations that

experienced decreasing body mass (i.e., dwarfing) were common amongst

many island biotas throughout the world, including the islands of southeast

Asia (rhinocerotids, proboscidians, hominins; Anderson, 1984; Brown et al.,

2004; Morwood, et al., 2004; Diamond, 2004), New Guinea (macropods &

diprotodontids; Flannery, 1999b), and the Mediterranean (mastodonts,

39

hippopotamids; Martin, 1984). Endemic island mammalian faunas originated

by the arrival of mainland species swimming or rafting, or by movement over

landbridges that were open for short periods of time. Isolated islands would

have provided short-term habitats for species concentrations (King &

Saunders, 1984). Dwarfed lineages show a marked decrease in size in

comparison to their mainland precursors, reflecting incipient dwarfing in

response to their insular distributions (Lister, 2004). Dwarfing has also been

documented in several continental mammal populations (Marshall &

Currucini, 1978; Forsten, 1991; Guthrie, 2003). Dwarfing on larger

landmasses may have been an evolutionary response to a decline in nutrient

quality of plant food, and hence, may have been an appropriate response to

the increasing unpredictability in the length of growing seasons (Marshall &

Currucini, 1978). Larger-sized species exhibited the largest-size reduction.

Hence, dwarfing was related to body size and was an adaptive process that

may have resulted from density dependent factors (i.e., resource-limited

systems). However, pressure from human hunting may also be responsible

for selecting larger-sized individuals (Davis, 1981; McDonald, 1984;

Flannery, 1990). Human-induced processes may result in a shift for the

selection of early maturing dwarfs, thus providing a genetic basis for the shift.

However, dwarfing may be a process that is not open to all species. For

example, some large specialised browsing species can only maintain their

niches because their bodies are an essential physical and physiological

adjunct to their feeding adaptation (Murray, 1991). Grazing species may be

able to scale-down without shifting their adaptive zone (Murray, 1991).

Regardless of the causes of dwarfism, no hypothesis directly explains why

some continental lineages tended towards dwarfism and others did not.

Additionally, most interpretations that dwarfing took place are drawn on the

basis of endpoints only, with only a few rare cases where continuous body

size reduction over time was observed (e.g., Guthrie, 2003). The exact cause

of dwarfed lineages of species on continents is unclear, but such dwarfing

may be the result of resource-limited systems, human predation pressures,

or a combination of both.

40

Multicausal or ecological models of extinction

Disagreement over a single cause of megafaunal extinction has led to the

development of hypotheses invoking a muliticausal or ecological explanation

(Calaby, 1976; Murray, 1991; Field & Dodson, 1999; Barnosky et al., 2004b;

Wroe, 2005). Emerging evidence suggests that humans contributed to the

extinctions in some areas, but were not solely responsible for extinctions

everywhere (Barnosky et al., 2004b). The intersection of human populations

and impacts of pronounced climate change possibly drove the geography

and timing of megafaunal extinctions in the Northern Hemisphere (Gonzalez,

2000; Barnosky et al., 2004b; McNeil et al., 2005; Boeskorov, 2006).

Mulitcausal models of extinction have also been suggested for Australia

(Field & Dodson, 1999; Barnosky et al., 2004b; Trueman et al., 2005).

However, like other hypotheses regarding megafaunal extinction, they are

limited by imprecise chronologies (Field & Dodson, 1999; Barnosky et al.,

2004b). Specific mulitcausal or ecological models include the keystone

herbivore hypothesis, and self-organised instability model.

Keystone herbivore model

The keystone megafauna extinction hypothesis links an assumption of both

overkill and climate hypotheses, principally, that there are strong interactions

between animal grazing and ecosystem processes (Owen-Smith, 1987;

1988; Zimov et al., 1995). Mammals, particularly large-sized taxa, can act as

keystone species to influence ecosystem dynamics (Sinclair, 2003; Haynes,

2006). The keystone herbivore Pleistocene extinction model was originally

based on the ecology of extant browsing and grazing megaherbivores (i.e.,

terrestrial herbivores >1000 kg; Owen-Smith, 1988), such as elephants

(Loxodonta africana) and white rhinoceros (and Ceratotherium simum) in

Africa. Megaherbivores, particularly adults, are immune to non-human

predation effects. Thus, those species may attain high population densities

such that they can radically transform vegetation structure and maintain

vegetative mosaics (Owen-Smith, 1987; 1988; Sinclair, 2003). For example,

extant elephant populations in Africa can change closed woodlands or

thickets to grassy savannah (Owen-Smith, 1987; 1988; Haynes, 2006).

41

Grazing white rhinoceros can transform tall grasslands into more nutritious

short grasslands (Owen-Smith, 1987; 1988). Thus, selective removal of

Pleistocene megaherbivores, either through synergistic effects such as

climate change or overhunting, may have promoted reverse changes to plant

communities. Such habitat changes may have produced dramatic cascading

effects on smaller-sized species. The conversion of heterogeneous

woodlands and grasslands to homogeneous forest and prairie grasslands in

North America during the late Pleistocene may be a consequence of the

removal of megaherbivores (Owen-Smith, 1987; 1988). Zimov et al. (1995)

suggested that the removal of keystone species through over-hunting in the

late Pleistocene Beringia resulted in the conversion of a vegetation mosaic

with abundant grass-dominated steppe to a mosaic dominated by moss

tundra. Removal of megaherbivores in Australia may have triggered an

expansion of shrublands and scrub, and led to the contraction of

heterogeneous woodlands and grasslands (Johnson, 2005a). However,

since many continental Pleistocene glacial maxima were characterised by an

increase in the homogeneity of habitats (e.g., Hope et al., 2004),

differentiating between natural climatically-driven versus anthropogenically-

driven vegetation changes in the last glacial maximum is difficult.

A major issue relating to the validity of the keystone species extinction

model is the timing of when megaherbivores went extinct in relation to

smaller-sized taxa. The basic prediction of the model is that keystone taxa,

such as proboscidians, should be the first to disappear in the fossil record

(Barnosky et al., 2004b), as observed for South American representatives

(Ficcarelli et al., 1997). However, in Eurasia, Alaska and central North

America, proboscidians were among the last taxa to become extinct

(Vasil’ev, 2001; Stuart et al., 2002; 2004; MacPhee et al., 2002; Guthrie,

2003; 2004; Fiedel & Haynes, 2004; Kuzman & Orlova, 2004). In Australia,

only two genera of megaherbivores were present during the late Pleistocene,

Diprotodon and Zygomaturus. Extinction chronologies for Australia are much

less secure than those for the Americas and Eurasia. However, current data

suggest that those genera also were among the last to disappear (Field &

Dodson, 1999; Roberts et al., 2001a). Hence, the keystone herbivore

extinction model is not supported for Australia. Regardless, the sudden

42

removal of megaherbivores would presumably have had dramatic effects on

late Pleistocene plant communities (Owen-Smith, 1987, Haynes, 2006).

Self-Organised Instability

An additional ecological-based megafauna extinction hypothesis that has

received little attention thus far, is the self-organised instability (SOI)

hypothesis proposed for Australia by Forster (2003). The SOI megafauna

extinction hypothesis was developed following recent advancements in the

study of ecosystem complexity (e.g., Bak, 1996; Solé et al., 2002). Forster

(2003) suggested that immigration of fauna from southeast Asia coupled with

the speciation of existing taxa in response to increasing aridity since the late

Pliocene (Gallagher et al., 2003) led to a level of self-organised instability of

Australian Pleistocene faunal assemblages. Increases in the immigration of

humans during the late Pleistocene also may have increased the connectivity

of other faunal elements into Australia. The combined effect was to make

megafauna inherently susceptible to extinction. However, the hypothesis has

yet to be tested. Several species entered Australia via northern landbridges

during the late Tertiary and Quaternary. ‘Old endemic’ rodents arrived 7-5

Ma (Watts & Aslin, 1981; Godthelp, 1990). ‘New endemic’ rodents and other

small, non-volant mammals entered Australia via xeric corridors throughout

the Pleistocene (Taylor & Horner, 1973; Godthelp, 1990; Flannery, 1995),

although most arrivals appear to be Holocene events (Winter, 1997).

However, the rate, timing, and effect on endemic fauna resulting from such

Plio-Holocene immigrations are unknown. Several taxa also entered North

America during the Tertiary-Quaternary. The extinct Harlon’s ground sloth

(Paramylodon harlani), and mammoths (Mammuthus spp.) arose from South

America and Eurasia respectively, and commonly occurred sympatrically in

the Pleistocene North America (McDonald & Pelikan, 2006). Although both

taxa occurred in a similar habitat and filled a similar niche, minor differences

in their ecologies allowed them to avoid competition, thus enriching the North

American Pleistocene mammalian fauna. Moreover, there is no evidence

that their appearance in North America resulted in the extinction of any

native species (McDonald & Pelikan, 2006). Generally, at least for Australia,

the SOI megafauna extinction hypothesis is still in its infancy and is difficult

43

to test with the current paucity of data on rates of faunal immigration and

speciation during the Pleistocene (Forster, 2003).

Chronologies

Critical to the understanding of the causes of megafaunal extinction is the

development of accurate chronologies of human colonisation and species

extinctions. Even in areas, such as the Americas, where chronologies of

human arrival and megafauna extinction appear to be relatively well

established, controversy concerning the causes of extinction remains

(Barnosky et al., 2004b). One of the main issues concerning the timing of

human arrival and megafaunal extinctions in regions such as Australia, is

that such events may have occurred just outside the practical limits of

radiocarbon dating. Several dates of human arrival have been suggested,

ranging from >100 ka (Wang et al., 1998), >60 ka (Roberts & Jones, 1994;

Thorne et al., 1999), and 50-42 ka (Fifield et al., 2001; Gillespie, 2002;

Bowler et al., 2003), with most of those dates obtained from optically

stimulated luminescence (OSL), electron spin resonance (ESR), U-series

dating, or radiocarbon dating techniques. A recent review suggested that

humans had colonised the continent by 45-42 ka, and that older dates are

not well supported (O’Connell & Allen, 2004).

Until recently, specific chronologies of Australian megafauna extinctions

were lacking. Baynes (1999) reviewed almost 100 radiocarbon dates that

were associated with Australian megafauna remains, but rejected most dates

as being unreliable, including all dates younger than 28 ka. A major problem

for the accurate dating of Australian megafauna deposits is that most known

deposits are beyond the practical limit of the radiocarbon dating technique

(Gillespie, 2002). Therefore, Roberts et al. (2001a) developed chronologies

for megafauna using OSL and U/Th dating methods and suggested that the

last Australian megafauna occurred at ~46.4 ka. However, their sampling

procedures and subsequent interpretations have been strongly criticised

(Field & Fullager 2001; Wroe et al., 2004). Aside from the fact that the 46.4

ka date falls near the limit of effective radiocarbon dating (Gillespie, 2002),

Roberts et al. (2001) analysed only deposits that contain articulated remains

of megafauna. Although the sampling strategy was aimed at limiting the

44

possibility of reworking of older megafaunal remains into younger deposits, it

automatically excludes the majority of known late Pleistocene megafauna

sites, including, for example, most archaeological sites (e.g., Field &

Fullagar, 2001). Many such sites have been dated younger than 46.4 ka,

including Cuddie Springs, where rigorous geochemical assessment

suggested minimal reworking of fossil material (Trueman et al., 2005). The

stratigraphic integrity and provenance of fossils from younger deposits may

be questioned (Baynes, 1999), but reworking cannot be assessed on the

basis of dating alone (Field & Fullagar, 2001; Trueman et al., 2005). Specific

hypotheses of reworking can be tested by using data from disciplines, such

as taphonomy, sedimentology, geochemistry, archaeology and

geomorphology, to independently establish the context and accumulation

processes of a fossil deposit (e.g., Behrensmeyer, 1988; Lyman 1994;

Trueman et al., 2005).

Roberts et al. (2001a) dated 28 deposits from several widely spaced

geographic regions, but dismissed the results of 19 of those sites because

they either lacked articulated skeletons or to reduce bias for statistical

analysis. Hence, the effective sample size used to predict the timing of the

extinction event was only nine ‘securely’ dated sites. Perhaps more

importantly, stratigraphic, sedimentologic, taphonomic, and palaeoecologic

aspects of the majority of those nine sites remain unpublished. Hence, the

stratigraphic provenance of fossil material and dating results from those sites

cannot be independently assessed. Regardless, the two youngest deposits

were from southwestern Western Australia (Kudjal Yalgah Cave, 46 ± 2 ka)

and southeastern Queensland (Ned’s Gully, 47 ± 4). Roberts et al. (2001a)

subsequently concluded that megafauna went extinct synchronously.

However, of 25 Pleistocene megafaunal genera, 20 survived in temperate

Australia until at least 80 ka, and only six megafaunal genera were present

until at least 46 ka (Roberts et al., 2001a). Thus, on the basis of those data,

the extinction of the Australian Pleistocene megafauna appears to have been

progressive, not an immediate or synchronous event as suggested by

Roberts et al. (2001a). Additionally, assuming decreasing diversity in

megafauna communities from >80 ka - 80 ka, and 80 ka - 46 ka, and thus,

potentially predating human arrival, a significant role is posited for non-

45

anthropogenic mechanisms, such as climate, in driving megafauna

extinction. A combination of climate deterioration and human arrival post-50

ka may have compounded on an extinction ‘event’ already underway. That

interpretation may be supported by evidence from the Cuddie Springs

archaeological deposit (Field & Dodson, 1999; Trueman et al., 2005). A

combination of geochemical analyses and radiocarbon dating indicated that

at that site, megafauna extinction was attritional, with megafauna suffering

extinction behind a backdrop of climatic deterioration ~30 ka (Field and

Dodson, 1999; Trueman et al., 2005).

Despite the lack of agreement on the precise timing of late Pleistocene

human colonisation and megafaunal extinction, several hypotheses have

been developed for anthropogenic or climatic models of Australian

megafauna extinction. Many of those hypotheses rely on, or can be tested

with, the chronologies presented by Roberts et al. (2001a).

For example, Johnson and Prideaux (2004) suggested that megafauna

extinction was not related to their feeding ecology, i.e., browsers or grazers.

Rather, extinction was related to body size, a hypothesis echoed by Brook

and Bowman (2004). That interpretation is in contrast to Miller et al. (1999;

2005a) who argued that dietary specialisation of megafauna was a causative

factor in their extinction. Regardless, the Johnson and Prideaux (2004)

hypothesis is not supported unless all Australian Pleistocene megafauna

went extinct synchronously. Thus, Johnson and Prideaux (2004) followed

Roberts et al. (2001a) and assumed that all browsing and grazing

Pleistocene taxa suffered synchronous extinction ~46 ka. However, there are

very limited, or absent, chronologies for several species and even for some

of the genera that Johnson and Prideaux (2004) discussed in particular. For

example, there is little or no systematic evidence that some taxa (e.g.,

Phascolomys spp., Ramsayia spp., Kolopsis watutense., Macropus

piltonensis) even survived until the late Pleistocene (Roberts et al., 2001a).

Additionally, there appears to be a high degree of confusion in the literature

regarding the ecological characteristics of extinct megafaunal species,

principally, in body weight and dietary estimates (see also Johnson and

Prideaux, 2004). Subjectively determined body weight estimates that were

taken from the literature (e.g., Long et al., 2002) and utilised by Johnson and

46

Prideaux (2004), contrast significantly with other body weight estimates that

were derived using other deterministic methods (e.g., femoral circumference

or endocranial volume analyses) (e.g., Murray, 1991, Wroe et al., 1999;

2003a, b; Smith et al., 2003). In some cases, such estimates vary in the

range of almost 200% (e.g., Diprotodon optatum 1150 kg – 2786 kg).

Similarly, interpretations of megafauna diets derived from the literature and

utilised by Johnson and Prideaux (2004) appear to vary significantly. For

example, Johnson and Prideaux (2004) assigned Protemnodon anak, P.

brehus, and P. roecheus as browsers, whereas other interpretations

suggested that those Protemnodon congenors were grazers (Bartholomai,

1973a) or mixed feeders (Murray, 1984). Body mass and diet are among the

most critical aspects of an organism’s ecology, and therefore, palaeoecology

relies on accurate estimates of those fundamental aspects (Alexander, 1998;

Witt & Ayliffe, 2001). Generally, body weight and dietary estimates of many

Australian megafaunal groups are badly in need of revision.

Lyons et al. (2004a) observed that megafauna extinctions in Australia and

on other continents occurred rapidly following initial human colonisation, and

posited a major role for human hunting in forcing the extinctions. However,

as with Johnson and Prideaux (2004), Lyons et al. (2004a) assumed that all

Australian megafauna taxa suffered extinction at 46 ka. However, Lyons et

al. (2004a) appears to have inadvertently overlooked evidence from the

Cuddie Springs archaeological deposits that indicates a human-megafauna

continental overlap of 15 ka (Field & Dodson, 1999; Trueman et al., 2005).

Lyons et al. (2004a) also suggested that there was no evidence of climate

change around 46 ka, and thus, that provided additional support for an

anthropogenic component to megafauna extinction. However, several

references utilised by Lyons et al. (2001a) that suggested an absence of

climate change at the time of megafaunal extinction are outdated (e.g.,

Kershaw, 1974; 1978; 1986; 1994). More recent advancements in dating and

other palaeoecological analytical techniques have established fluctuating

climatic trends towards aridity coupled with dramatic vegetational

disturbances from 50 ka (Longmore & Heijnis, 1999; Johnson et al., 1999;

Turney et al., 2001b; 2004; Bowler et al., 2003; Hope et al., 2004).

47

Horton (1984; 2000) suggested that late Pleistocene aridity expanded

from the centre of Australia outwards, and fragmented and compressed

megafauna habitats to the margins of the continent. Megafauna populations

were restricted to those isolated pockets of habitat and were unable to

migrate due to resource tethering effects. Finally, over-competition between

individuals in those restricted habitats led to local extinctions of megafaunal

populations (Horton, 1984; 2000). Such events may have been repetitive in

different regions, eventually leading to the extinction of a species.

Essentially, the hypothesis suggests that megafauna extinction was

asynchronous, and occurred in specific geographic patterns, primarily, from

the arid centre outwards over thousands of years during the approach of the

last glacial maximum (Horton, 1984; 2000). Hence, the hypothesis does not

require an anthropogenic role in the extinctions. Testing that hypothesis is

difficult considering the lack of accurate chronologies for many megafaunal

taxa. However, chronologies for the giant bird, Genyornis newtoni, appear to

be the most comprehensive amongst Australian megafaunal taxa. Miller et

al. (1999; 2005a) demonstrated G. newtoni extinction in the central arid zone

of Australia around 45 ka. Field and Dodson (1999), Roberts et al. (2001a)

and Trueman et al. (2005) demonstrated that G. newtoni occurs in a more

eastern (currently semi-arid), undisturbed 30 ka deposit (Cuddie Springs)

alongside other megafaunal taxa. Thus, on the basis of that evidence, there

is some support for Horton’s (1984; 2000) climate-change hypothesis in the

geographic and temporal pattern of G. newtoni extinction. Obviously, more

dating from widely separated geographic sites is required to further test that

hypothesis. However, there is some evidence based on other palaeoclimate

proxies to support the broad contention of coastward aridification in the

Pleistocene (Nanson et al., 1992).

Johnson (2005b) considered how interpretations of megafauna extinction

may be changed on the presumption that megafauna survived beyond 46 ka.

He used chronologies presented in Roberts et al. (2001a) and additional

references (see Johnson, 2005b) for megafauna deposits that have been

dated younger than 46 ka and contained disarticulated remains. Although

several Sahulian (Australia-New Guinea) megafauna deposits have been

dated younger than 46 ka, Johnson (2005b) recognised that most of those

48

deposits require rigorous assessment to evaluate the potential for the

reworking of sediments and/or fossil material. Thus, Johnson’s (2005b)

analysis was simply presented as a hypothetical scenario, on the

presumption that those young megafauna deposits have accurate dates and

that the fossil material was not reworked. Johnson (2005b) concluded that

attritional anthropogenic overkill, rather than blitzkrieg or climate change,

drove megafauna extinction. A potentially long overlap between humans and

megafauna automatically refutes a blitzkrieg extinction model (Johnson,

2005b). Additionally, Johnson (2005b) observed that there was no

discernible spatial patterning in megafaunal extinction and rejected Horton’s

(1984; 2000) climate change extinction hypothesis. However, Horton (1984;

2000) only used distance from the coastline as a descriptive proxy for

rainfall, but recognised that precipitation does not uniformally increase from

the continent’s centre outwards (i.e., in many parts of Australia, the current

semi-arid and arid zones extend to the continental margins). Thus, distance

from the current coastline cannot be used as a reliable proxy in the way that

Johnson (2005b) applied it (Wroe & Field, in press). In arriving at his

conclusion, Johnson (2005b) stated that continental megafaunal populations

declined dramatically 50-46 ka following initial human arrival. However, the

data sets utilised by Johnson (2005b) are based primarily on temporal

presence or absence patterns of megafaunal taxa. Data relating to

megafaunal community population dynamics from integrated stratigraphic

successions from many of those late Pleistocene sites, particularly the 50-46

ka deposits, are absent or remain undocumented. Therefore, it is not

possible to analyse the response of specific local populations to human

arrival and/or climate change, nor to demonstrate population declines on the

basis of the available data. Johnson’s (2005b) attritional overkill hypothesis

may also be challenged using the same data set simply by looking at

diversity patterns of megafauna taxa in 50-46 ka deposits versus <46 ka

deposits. Chronologies are available for 12 species in 10 genera for 50-46 ka

deposits, and 22 species in 15 genera for <46 ka deposits (Johnson, 2005b,

and references therein). Thus, rather than a dramatic decline in megafauna

diversity after 50 ka, those data suggest increasing diversity and possible

speciation events alongside a backdrop of increased human presence and

49

climate deterioration during and after the last glacial maximum. Of course,

that is highly unlikely given the dramatic events and unfavourable conditions

surrounding the last glacial maximum. However, this example simply

highlights the need to more rigorously assess new sites and reassess

previously documented sites in terms of reworking and dating, before

extinction hypotheses can be adequately tested using existing data. As

Richard Wright observed in 1990, “megafaunal extinctions is a topic that now

requires rather more digging than talking!” (Wright et al., 1990). Fifteen years

later, the same can still be said for our current understanding of megafaunal

extinctions.

Most other recent hypotheses that support anthropogenic models of

Australian megafauna extinction (e.g., Diamond, 2001; Gillespie, 2002;

Johnson, 2002; Brook & Bowman, 2004; Fiedel & Haynes, 2004; Burney &

Flannery, 2005) rely on similar interpretations and on the conclusions of

Roberts et al. (2001a). Hence, they also are limited by imprecise and

incomplete chronologies. Due to an absence of congruence of chronometric

data, the case for an anthropogenically driven, continent-wide extinction has

yet to be demonstrated. Thus, in order to test specific hypotheses of

megafaunal extinction, it is important to have accurate age estimates of the

last occurrence of each species in various parts of the continent (Grayson,

1989). The establishment of faunal ranges may prove difficult in regions like

Australia owing to the low number of late Pleistocene fossil sites (Dodson et

al., 1993) and the age of many sites being near 40 ka, the practicable limit

for radiocarbon dating. Despite the criticisms directed at the interpretations of

Roberts et al. (2001a), their results add significantly to the understanding of

late Pleistocene extinctions in Australia. Roberts et al. (2001a) recognised

that several other late Pleistocene deposits need to be examined in detail

and dated accurately, a sentiment that has been echoed by many authors

(e.g., Field & Dodson, 1999; Barnosky et al., 2004b; Brook & Bowman, 2004;

Prideaux, 2004; Wroe et al., 2004). More complex models incorporating

detailed ecological analyses at differing regional scales are required to

resolve the issue of megafauna extinction (O’Connell & Allen, 2004; Burney

& Flannery, 2005).

50

DARLING DOWNS

The Darling Downs of southeastern Queensland, Australia, is a critical region

for understanding Australian megafaunal extinctions. It is one of the most

fossiliferous regions in Australia, with more than 50 megafauna-bearing fossil

localities known in a small (16 000 km2) geographic area (Molnar & Kurz,

1997). Roberts et al. (2001a) highlighted the importance of one of its

deposits (site QML783 = ‘Ned’s Gully’) and suggested that it is one of the

youngest in Australia that contains articulated remains of now extinct

megafauna.

Although fossil material has been collected from the Darling Downs since

the 1840’s, shortly following European settlement (Owen, 1877a), few

studies have attempted to document detailed palaeoecological aspects of its

fossil deposits. Although Bartholomai (1976b) and Molnar & Kurz (1997)

presented brief overviews of the Pleistocene faunas of the region, few

studies have addressed detailed stratigraphic, sedimentologic, taphonomic

or palaeoecologic aspects of specific megafauna deposits.

Geographical and geological settings

The Darling Downs is situated west of the Great Dividing Range in

southeastern Queensland. The region is bounded to the north by the Bunya

Mountains, south by the Herries Ranges, and slopes gently westwards into

the plains of central Australia. The Great Dividing Range forms a significant

watershed in eastern Australia and separates several significant drainage

basins. The Darling Downs catchments comprises the upper portion of the

extensive Murray-Darling drainage basin. With its low, rolling hills and plains,

the Darling Downs has today been transformed into a rich agricultural centre,

chiefly associated with grazing, grain and cotton growing. The majority of the

natural vegetation in the area has been altered to some extent by Europeans

(Thompson & Beckman, 1959; Fensham, 1998). However, early pioneers

such as Leichardt (in Bennett 1875) gave an insight into the Darling Downs

prior to the effects of European settlement. Leichardt was awed by the

extensive floodplains covered by grasses and herbs, and noted that open

woodlands were restricted to hillsides. That view was supported by a recent

51

review of vegetative surveys of the region from the early periods of European

settlement (Fensham & Fairfax, 1997).

During the Tertiary, a sequence of volcanic eruptions around the

Toowoomba region produced a series of predominantly basaltic flows

overlying Mesozoic sandstones (Thompson & Beckman, 1959). Dissection

and erosion of the sandstones and basalts during the Tertiary and

Quaternary developed several landforms in the region including the

Toowoomba Plateau, basaltic uplands, steep eastern slopes of the range,

and alluvial floodplains (Thompson & Beckman, 1959). Deep lateritic soils

developed from erosion of basalts along the eastern edge of the range.

Additional erosion of underlying sandstones and basalts led to the

development of dark clay, sand and silt, with abundant calcrete nodules, and

is characteristic of the extensive alluvial plains (Woods, 1960; Gill, 1978).

The sediments are alkaline as evidenced by the high amounts of preserved

calcareous materials (molluscs and calcretes; Gill, 1978). Fossils are

generally derived from the dark clay soils within the floodplains.

The fossil-bearing portion of the Darling Downs is roughly rectangular in

shape, 200 km long and 80 km wide (Molnar & Kurz, 1997). The long axis

runs parallel to the Great Dividing Range. The fossil-bearing portion of the

Darling Downs is divided into two sections (Molnar & Kurz, 1997). The

eastern Darling Downs is underlain predominantly by Pleistocene deposits

and is situated to the east of the Condamine River. The older, Pliocene

Chinchilla Local Fauna is located in the western Darling Downs (Bartholomai

& Woods, 1976).

Macintosh (1967), Gill (1978) and Sobbe (1990) provided limited

stratigraphies for sections along creeks of the eastern Darling Downs,

introducing units termed ‘Toolburra silt’, ‘Talgai pedoderm’ and ‘Ellinthorpe

clay’. However, those names have not seen subsequent use and are not

considered valid stratigraphic units (Baird, 1986; Molnar & Kurz, 1997).

Radiometric and optical dating, and biostratigraphic markers (e.g.,

Diprotodon spp. and Procoptodon spp.) place the age of the deposits within

the Pleistocene (Bartholomai, 1970; Gill, 1978; Molnar & Kurz, 1997;

Mackness & Godthelp, 2001; Roberts et al., 2001a). However, precise

stratigraphic and temporal relationships between Darling Downs deposits,

52

and other southeastern Queensland Pleistocene deposits such as those at

Gore (Bartholomai, 1977) and Texas (Archer, 1978a), are unclear.

Palaeoecology

Early landowners had a general lack of interest in, and knowledge about, the

fossils recovered from Darling Downs deposits, but that did not deter the

efforts of early collectors such as Bennett (Bennett, 1872; 1876) and

Broadbent (de Vis, 1885a). Subsequent collecting from the region continued

at varying rates, with a general focus on the recovery of large-sized

specimens. The majority of fossils recovered from the deposits have been

accessioned into the collections of the Queensland Museum, Brisbane.

Several studies have addressed the taxonomy of Pleistocene faunas from

the region. Several new species were described from the Darling Downs

during the 1800’s such as Meiolania oweni (Woodward, 1888),

Ornithorhynchus agilis (de Vis, 1885b), Diprotodon minor (Huxley, 1862),

and Sthenurus pales (de Vis, 1895). However, several of those species have

since been synonomised with previously erected taxa (e.g., O. agilis de Vis

1885b is a junior synonym of O. anatinus Shaw 1799; Archer et al., 1978).

Work on Darling Downs fossil faunas continued into the early 20th century by

Longman (e.g., 1916; 1924; 1936). More recently, Bartholomai (1963; 1966;

1967; 1970; 1972, 1973a, b; 1975; 1976a) provided seminal taxonomic

reviews of Pleistocene kangaroos and wallabies from the deposits, with

additional contributions from Flannery and Archer (1982; 1983), and

Prideaux (2004); Archer et al. (1978) reviewed the taxonomic status of a

Pleistocene Darling Downs platypus; Baird (1986) described Pleistocene

distributions of birds from the region; Molnar (1990) and Wilkinson (1995)

illustrated fossil material of extinct and extant varanids; and Sobbe (1990)

investigated Pleistocene ecological aspects of predator-prey interactions.

Few attempts have been made to present an overall picture of the region

during the Pleistocene. Both Bartholomai (1976b) and Molnar and Kurz

(1997) suggested that the presence of diverse grazing and browsing

megafauna taxa recovered from the deposits broadly indicated that vast

grasslands and woodlands existed during the Pleistocene. However, Molnar

and Kurz (1997) recognised that past collecting in the region focused on the

53

recovery of large-sized taxa, with smaller forms being overlooked. Hence,

palaeoenvironmental interpretations of Bartholomai (1976b) and Molnar &

Kurz (1997) are limited by the poorly known smaller forms. Since the mid-

1990’s, systematic collecting has focused on the recovery of both large and

small-sized taxa in a variety of deposits from the northern and southern

Darling Downs. The most extensive and diverse faunas have been recovered

from deposits within the Kings Creek catchment (southern Darling Downs).

Those faunas formed the primary focus for my investigation. Whereas

previous palaeoecological studies of Darling Downs fossil vertebrates were

concerned mainly with the taxonomy of fossil species, my project focused on

local and regional palaeoecological aspects of the Pleistocene Darling

Downs.

Kings Creek Catchment

Several Pleistocene megafauna deposits have been recorded in the Kings

Creek catchment (Figure 1). Such deposits are registered as Queensland

Museum Localities (QML) and include exposures in Kings Creek (QML100,

QML796, QML913, QML1396), Budgee Creek (QML782) and Ned’s Gully

(QML783). As with all deposits recorded from the Darling Downs, the

deposits of the Kings Creek catchment are predominantly fluvial in origin.

The preservation of fossil material includes rounded bone pebbles, complete,

but disarticulated skeletal elements, and complete articulated skeletons

(Molnar et al., 1999).

All analytical dating thus far attempted in the catchment confirms that the

deposits are late Pleistocene in age. Hendy et al. (1971) and Gill (1978)

used radiocarbon dating methods to date deposits at Talgai, Dalrymple

Creek, just west of the Kings Creek catchment. Charcoal and calcrete were

dated between 41 and 4 ka. However, megafaunal species were not

reported in association with those dates. Roberts et al. (2001a) used optical

stimulated luminescence (OSL) dating techniques and dated site QML783 (=

‘Ned’s Gully’) to 47 ± 4 ka. Typical Darling Downs megafauna recorded in the

deposit included articulated remains of Diprotodon optatum, Macropus titan,

and Protemnodon roechus (Roberts et al., 2001a). Little analytical dating has

54

been attempted for other deposits in the region. In general, the stratigraphic

relationships between deposits of the Kings Creek catchment are unknown.

Figure 1. Modern Kings Creek Catchment with heights (in metres) of surrounding peaks, the

main deposit (site QML796) and other deposits mentioned in the text (QML). GDR: Great

Dividing Range; KCC: Kings Creek Catchment; QML: Queensland Museum Locality.

Site QML796

I chose site QML796 as a major focus for my investigation of the Pleistocene

palaeoecological aspects of the region (Figure 1). Site QML796 (= ‘Sutton’s

Site’; Molnar & Kurz, 1997) is located in the northern bank of Kings Creek.

The exposed portion of the deposit is approximately 5 metres wide by 2

metres high. Several distinct sedimentary horizons are evident in the deposit.

A tentative stratigraphic assessment of the site suggested that deposition

occurred both in channel and overbank settings, thus allowing the testing of

specific taphonomic hypotheses.

Site QML796 is one of the most fossiliferous deposits in the Kings Creek

catchment. Fossil invertebrate and vertebrate remains are common

throughout each stratigraphic horizon, however, some horizons are more

fossiliferous than others. A diverse fauna was initially collected from the

deposit that included almost 20 taxa including members of the

Velesunionidae, Thiaridae, Teleosti, ?Anura, Chelidae, Agamidae,

55

Varanidae, Crocodylidae, Aves, ?Monotremata, Dasyuridae, ?Peramelidae,

Palorchestidae, Diprotodontidae, Vombatidae, Macropodinae and Muridae

(Molnar & Kurz, 1997). As the stratigraphy of the deposit indicated several

periods of deposition, the site was ideal for the examination of potential

species through time at a single locality. My investigations of site QML796

provided a detailed palaeoecological record of the region, and hence, forms

a baseline for comparison of other deposits, both for the Kings Creek

catchment, and for the broader Darling Downs, thus placing the deposits in a

national context. The Darling Downs may also become a region of

international significance for the testing of hypotheses regarding the global

Pleistocene extinction of the megafauna.

Excavation

Although site QML796 has been known for more than 20 years, collecting

has been dominated by amateur palaeontologists. Such collecting has

focused on the recovery of large-sized specimens, predominantly

megafaunal species, with little consideration of the stratigraphic provenance

of fossil material. Later excavations by the Queensland Museum (QM)

involved the general documentation of the stratigraphic units of the deposit.

Seven main stratigraphic units were identified (designated A1 through A7).

Fossils were recovered by in situ collecting and removal of bulk sediment for

sieving to target smaller specimens. All fossil material was labeled according

to the sedimentary horizon from which it was derived, and >10 m3 of

sediment were processed. The sediment was washed using graded sieves

ranging from 10 mm to 1 mm, and small bones were sorted following

techniques described in Andrews (1990). Such collecting procedures allowed

the recovery and association of both large and small-sized taxa.

More recent QUT-QM excavations involved a ‘top down’ excavation

approach. A 3 x 2 m plot was surveyed on the ground above the site, and 1 x

1 m quadrats were excavated in 10 cm increments using trowels and

brushes. Excavated layers were correlated to stratigraphic units on the

vertical sides of the pit. The excavation continued to the depth of 2.3 m

yielding an additional ~14 m3 of material. That methodology standardised the

56

method of collection and allowed the retrieval of detailed information of

species distributions within the deposit.

The manual sieving and sorting component of fossil material was

particularly time-consuming and labour intensive. However, numerous

volunteers provided assistance in those aspects during the course of the

research. Collectively, they contributed over 15 000 hours in manual labour.

The intensive efforts of such volunteers allowed several thousand kilograms

of sediment to be processed and allowed the retrieval of material and data

that would have been otherwise impossible to obtains in the required

timeframe.

Stratigraphy, sedimentology and taphonomy

The entire exposed section was measured and documented on vertical

surfaces during excavation. A 2.3 metre-long auger was used to probe

surrounding sediment to determine the lateral extent of particular beds.

Sediment samples from each stratigraphic unit were disaggregated using

alternating cycles of bleach and detergent, dried, and sieved using -2 to 4 phi

mesh sizes for grain size analysis. Subsamples were wet sieved to ensure

separation of the mud fraction. Lithofacies and fluvial architectural elements

were identified and assigned facies codes following the technique described

by Miall (1996). Differentiation and identification of calcrete followed Arakel

(1982). The stratigraphic and sedimentologic investigation of the deposit

allowed determination of the precise depositional setting.

Unfortunately, few studies have specifically investigated the depositional

processes and taphonomic modes of fossil accumulation of Australian

megafauna deposits (e.g., Baird, 1991; Long & Mackness, 1994; Van Huet,

1999; Brown & Wells, 2000). Hence, spatial and temporal constraints on the

palaeoecology of prehistoric Australian terrestrial communities are poorly

known, especially including those that encompass late Pleistocene

megafauna extinction. Studies that document taphonomic modes of bone

accumulation are particularly relevant in that they can aid recognition of

reworking and bias related to both accumulation processes and preservation.

Bias in the fossil record may affect diversity estimates, timing of extinction

events, and analysis of palaeobiological and palaeoenvironmental

57

parameters (Behrensmeyer, 1988; Lofgren et al., 1990). Where significant

taphonomic investigations have been undertaken in Australia, they have

primarily focused on megafauna species (e.g., Long & Mackness, 1994; Van

Huet, 1999; Brown & Wells, 2000) or on small-sized mammals that occur in

non-megafaunal deposits (e.g., McDowell, 1997; Kos, 2003a, b). A

significant deficiency exists in the interpretation of accumulations involving

both fluvial fossil deposits and non-mammal terrestrial vertebrate groups,

such as squamates. The latter is also a deficiency associated with

taphonomic studies throughout the world, as studies have generally focused

on mammals, with most other terrestrial vertebrates overlooked. The more

significant taphonomic studies of non-mammal vertebrates have focused on

larger-sized groups such as dinosaurs (e.g., Dodson, 1971; Eaton et al.,

1989; Smith, 1993) and marine reptiles (e.g. Martill, 1985; 1987). It is

generally assumed that the dispersal and accumulation of such groups follow

similar taphonomic pathways to mammals (Martin, 1999). The vertebrate

taphonomic component of this study focused on both mammals and non-

mammal vertebrates from the deposits. Identifiable cranial and post-cranial

material of terrestrial vertebrate species provided the basis for the

taphonomic study. Unidentifiable bone fragments were not used. Better

preserved specimens may yield more accurate palaeobiological and

palaeoecological information than unidentifiable fragments. However, it is

recognised that some components of the assemblages may have had

different taphonomic pathways leading to their final deposition.

The unit of element representation included MNI (minimum number of

individuals; equivalent to NISP [number of identified specimens] following

Badgely, 1986), and MNE (minimum number of elements; Lyman, 1994). For

vertebrates, calculation of MNI was based mostly on dentary and maxillary

remains, except in the case of fish, frogs, turtles and some squamates,

where vertebrae, pelves, carapace/plastron fragments and osteoderms were

used, respectively. I conducted rarefaction analyses on taxon abundance

data for each assemblage to test for potential bias introduced by differences

in sample sizes. Diversity patterns using the rarifed data sets were compared

between assemblages of standardised subsample sizes with independent

Kolmogorov-Smirnov two-sample statistical tests (Jamniczky et al., 2003;

58

Payne, 2003). Additionally, taxon abundance data from each assemblage

were combined, and bootstrapping analyses (1000 replicates with

resampling) were conducted to obtain 95% confidence intervals for the

estimate of N taxa in a given assemblage.

The taphonomic study investigated the range of characteristics relating to

skeletal preservation, relative abundance of skeletal elements, breakage and

fracture patterns, and relative degree of abrasion of fossil material

recovered. Those analyses demonstrated the utility of lithofacies and

depositional environment analysis for interpreting different taphonomic

accumulation patterns of both large- and small-sized taxa within the deposit.

Such analysis was crucial for constraining full palaeoecological information in

the fossil fauna.

Orientation of large freshwater bivalves (Velesunio ambiguus) and bones

generally larger than 2 cm were measured in situ with the angles between

long axes and north recorded. In situ bivalve taphonomy was evaluated

using the coexistence index of left and right valves (Cv) of V. ambiguus. Cv

was calculated using the equation:

1

211V

VVCv

−−= (1)

where V1 is the greater number of valves and V2 is the lesser number of

valves (after Shimoyama & Hamano, 1990). Cv values range between 0 and

1 and measure the deviation from the expected 1:1 ratio. Additionally, χ2

tests were computed to test for preservation differences between bivalves.

The attitude (i.e., concave up or convex up) of V. ambiguus valves was also

documented. Recorded orientations of fossil material allowed for the

documentation of aspects relating to palaeocurrent direction.

Kolmogorov-Smirnov two-sample statistical tests and χ2 analyses, were

performed using SPSS © statistical software. Rarefaction and bootstrapping

analyses were conducted using PAST © statistical software (Hammer et al.,

2001). All correlations were considered to be significant at the 95%

confidence level.

59

Palaeoecology

A multifaceted investigation of the fossil fauna was designed that allowed the

retrieval of high resolution palaeoecological data. Morphological and

morphometrical techniques were used to taxonomically identify and

characterise the fossil material. Comparative specimens were accessible

within the Queensland Museum collections. Ecological aspects of extant taxa

occurring as fossils in the deposit were drawn by analogy to modern

populations. Ecological aspects of extant species were derived from Beesley

et al. (1998) and Lamprell and Healy (1998) for molluscs, Cogger (2000) for

reptiles, and Strahan (1995) for mammals. Ecologies of fossil taxa occurring

in the deposit were largely derived from Bartholomai (1973a; 1975), Murray

(1984; 1991) and Flannery (1990). Previous palaeoenvironmental

interpretations of the Darling Downs have been based on the inferred

ecologies of extinct megafauna (e.g., Bartholomai, 1976b; Molnar & Kurz,

1997). However, extant species that occur in fossil assemblages form a more

rational basis for palaeoenvironmental interpretations (Lundelius, 1983), and

the value of using small-sized taxa in reconstructing past environments is

increasingly being documented (Brothwell & Jones, 1978; Andrews, 1990;

Vigne & Valladas, 1996). Small-size taxa generally have smaller home

ranges, more specific habitat requirements and shorter life spans, making

them more useful for habitat reconstruction than larger-sized taxa. The

small-sized taxa of site QML796 were used in conjunction with megafaunal

species to make interpretations regarding Darling Downs

palaeoenvironments.

Ecological characteristics (e.g., locomotory or feeding behaviours) of

mammalian assemblages within the deposit were calculated. Andrews et al.

(1979) demonstrated that the community structure of modern mammal

communities from similar modern habitat types is consistent, even where a

comparison of taxa between habitat types indicates few or no species in

common. Habitats of mammalian communities can be predicted on the basis

of their ecological diversity. Hence, establishing the community structure of

modern mammal faunas from particular habitats and subsequent

comparison with the community structure of fossil mammal assemblages has

predictive value for assessing palaeohabitats (Andrews et al., 1979). Thus,

60

aspects of community structure of modern Australian mammalian faunas

were compared with the community structure of fossil mammal assemblages

from site QML796, following methodology described in Andrews et al. (1979).

The quantification of ecological relationships between modern and fossil

assemblages were assessed statistically with bivariate Pearson analyses

using SPPS © statistical software. Correlations were considered to be

significant at the 95% confidence level.

The ability to quantify diversity is an important tool when attempting to

understand community structure (Vermeij and Leighton 2003). There are

several different ways to estimate the diversity of an assemblage or

community. One of the most simple diversity estimates is by comparison of

the total number of species recorded between assemblages. However, such

estimates of species richness do not take into account several major aspects

of diversity including equability or evenness of the relative abundance of

species, or heterogeneity of the fauna (Willig, 2003). Several indices have

been developed that attempt to take into account species abundance and

evenness, and may provide important information about rarity and

commonness of particular species within a community or assemblage (Buzas

and Hayek, 2005). Diversity estimates for site QML796 were based on

Simpson, Shannon-Weiner, Pielou, and Whittaker diversity indices, and

MacArthur rank abundance models for terrestrial species from each of the

main fossiliferous horizons.

The Simpson’s heterogeneity index (D) is calculated by the formula:

( )( )

1

11

=

��

��

�

−−

=�

i

NNnn

D

s

ii (2)

where s is the total number of species, ni is the number of individuals i in the

sample, and N is the total number of species in the sample. D ranges

between 0 and 1, and is larger for samples with less heterogeneity. That

relationship is neither logical nor intuitive, so the relationship is inverted with

D being subtracted from 1 so that lower values reflect less heterogeneity

(Rose, 1981).

61

The Shannon-Weiner heterogeneity index (H') is among the most widely

used indices of diversity and is calculated by the formula:

1

ln'

=

−= �i

ppH

s

ii (3)

where s is the total number of species in a sample and p is the frequency of

the ith species. The index is primarily used as a measure of heterogeneity or

mixed diversity, but also reflects evenness.

The evenness component of heterogeneity is measured using several

indices. Among the most simple is Pielou’s evenness index calculated by the

formula:

sH

Jln

'= (4)

The calculation is derived from the result of H' and number of species in the

sample (s).

An additional index of evenness is the Whittaker index (E), which is

calculated using the formula:

( )spps

Eloglog 1 −

= (5)

where s is the number of species, pi is the frequency of the most common

species, and ps is the frequency of the rarest species.

Each diversity index has limitations, but the indices can be highly

informative regarding community structure (Buzas and Hayek, 2005).

Diversity and evenness may also be estimated using hypothetical models

of rank abundance of species within a given community or assemblage. Two

main models of the hypothetical distribution of species within a given

community were developed by MacArthur (1957; 1960). The ‘dependent

model’ (as hypothesis I in MacArthur, 1957) predicts that the relative

abundance of any species is dependent on the relative abundance of all

other species within a fauna. Thus, the relative abundance �

��

mN r of the rth

rarest species is calculated by the formula:

62

( )1

111

=+−

= �

iinnm

Nr

r

(6)

where m is the total number of individuals in a fauna, n is the total number of

species in the fauna, and Nr is the abundance of the rth rarest species. Here,

m is the total MNI and Nr is the MNI of the rth species. If relative abundance

is plotted against the logarithm of the rank abundance, the resulting curve is

nearly linear. MacArthur (1957) demonstrated that certain bird communities

from homogeneously diverse tropical and temperate forests fit the dependent

model hypothesis.

The ‘independent model’ (as hypothesis II of MacArthur, 1957) predicts

that the relative abundance of species r is independent of all other species

within a given fauna. The relative abundance mN r of the rth rarest species is

calculated by the formula:

( ) ( )( )n

rnrnmN r −−+−

=1

(7)

where n is the number of species in the fauna and r is the rank abundance of

species r. Here, rank is based on the abundance rather than rarity such that

1+−= rni . The model predicts that the common species are commoner and

rare species are rarer than that predicted by the ‘dependent model’.

Hutchinson (1961) observed independent model-type distributions of

diatoms, arthropods and plankton species in heterogeneous environments.

Dating

Dating the deposit is a critical aspect of the investigation. Accurate dating is

crucial for testing the previous reported ages for the region, establishing a

reliable chronology for the deposits, and for better understanding the timing

and means of extinction of many species. Dating the succession will also

support investigations of the systematics and phylogenetics of several

species that have Pleistocene records within the deposit. Samples of

bivalves (Velesunio ambiguus), charcoal and bone were submitted to

ANSTO (Australian Nuclear Science and Technology Organisation; Lawson

63

et al., 2000) for the purpose of accelerator mass spectrometry (AMS) 14C

dating. Only complete, conjoined bivalves were submitted for dating, as they

are unlikely to have been reworked from older units. V. ambiguus, like most

Unionoidea, have the ability to burrow (Walker, 1981). Hence, it is possible

that individuals selected for dating could have burrowed into sediment older

than that in which they lived. However, at site QML796, stratigraphic and

sedimentologic sequences are preserved intact and there is no evidence of

extensive burrowing of bivalves (see Chapter 4). Additionally, bivalves

selected for dating included only those that were lying with their valves

horizontal in the sediment and not in ‘growth’ or ‘burrowing’ positions (i.e.,

valves in vertical positions). Those individuals are presumed to have been

deposited in that position and were unlikely to have burrowed into older

sedimentary horizons

Selection of bivalves and charcoal samples for dating followed the dating

selection criteria established by Meltzer and Mead (1985). Samples were

collected from stratigraphic horizons containing megafauna and other small-

sized taxa that were entirely capped above and below by different sediments.

Results obtained from the dating of bivalves or charcoal indicate the

approximate time of deposition.

Bone samples from site QML796 were submitted to ACQUIRE (Advanced

Centre for Queensland University Isotope Research Excellence, University of

Queensland) for U/Th dating. Bone submitted for dating using both AMS 14C

and U/Th dating methods included near complete megafauna crania and

dentaries, isolated teeth, and complete post-cranial elements. Specimens

selected were well-preserved, relatively complete, and unabraded. Hence,

the selection criteria targeted fossil material that was particularly well

preserved, and highly unlikely to have been transported far or reworked. U-

series dating is based on the premise that U is taken up from the

environment by bone apatites that scavenge U, but exclude Th, during

diagenesis. The age is calculated by determining the amount of 230Th that

was produced by the decay of 238U (via intermediate isotope 234U). Since

bones are open systems for uranium, in most cases the U/Th dates

represent the mean ages of the U-uptake history and thus the minimum ages

of deposition (Simpson & Grün, 1998; Thorne et al., 1999; Zhao et al., 2001).

64

Meltzer and Mead (1985) considered that direct dating of fossil bone

represents a ‘strong’ association between fauna and deposition time and is

desirable for securely dating fossil assemblages.

Correlation to other Kings Creek deposits

Other Kings Creek catchment megafauna-bearing deposits were examined

to determine litho- and/or biostratigraphic relationships to QML796. Such

deposits included sites QML100, QML913, QML1396 (Kings Creek),

QML782 (Budgee Creek), and QML783 (Ned’s Gully) (Figure 1). Fossil

material was previously collected from each of those deposits and was

available for study in the Queensland Museum. However, additional material

was also collected from each of those localities using excavation techniques

similar to those utilised at site QML796, but to a lesser magnitude.

Stratigraphic, sedimentologic, taphonomic and palaeoecologic characteristics

were examined based on techniques used at QML796. Due to financial

constraints, analytical dating was attempted only for QML796 and QML1396.

The ultimate aim of such correlations was to provide a chronology for the

depositional history of Kings Creek catchment fossil deposits. Biocorrelation

between sites may allow species to be studied at varying temporal and

spatial scales.

SUMMARY

The ability to answer questions regarding ancient populations and species

may allow us to anticipate changes in modern ecosystems subject to

environmental change (Barnosky et al., 2004a). Environmental records that

have been derived through the investigation of Quaternary environments and

the mechanisms that have been proposed to account for the observed

changes, provide a vital resource for modeling an understanding of the

global environment (Willis et al., 2004). Additionally, the knowledge of both

the history and modern conditions of lineages are required to best determine

a species’ current conservation status and make reasoned predictions about

its future survival.

65

Essentially, to resolve the issue of late Pleistocene Australian megafauna

extinction, several issues require investigation including: 1) the temporal and

spatial extinction patterns of megafaunal species (Horton, 1984; Grayson,

1989; Gonzalez et al., 2000; Stuart et al., 2002; 2004); 2) the temporal and

spatial patterns of arrival and dispersal of human colonisers in Australia

(O’Connell & Allen, 2004); 3) determining what megafaunal species co-

occurred with humans and the nature of the interaction (direct [e.g. hunting]

or indirect [e.g. habitat modification via burning]) (Horton, 1984; Field &

Dodson, 1999; Prideaux, 2004; Arroyo-Cabrales et al., 2006); 4) determining

whether that interaction was a casual factor for the extinction (Trueman et

al., 2005); and 5) discriminating anthropogenic factors from natural inherent

climatic variability (Diamond, 1989b; Burney & Flannery, 2005). Confusion

surrounding the timing and causes of Australian megafauna extinctions is

due primarily to the paucity of well-dated late Pleistocene megafauna

deposits. A combination of more rigorous dating and increasingly complex

models incorporating detailed ecological analyses at differing regional scales

are required to resolve the issue of megafauna extinction.

Previous investigations of the Pleistocene Darling Downs place the age of

the deposits close to the terminal extinction ‘event’ of the megafauna. Hence,

detailed investigation of its deposits and Pleistocene faunas may have

critical implications for the understanding of regional and continental

megafauna extinction.

66

PUBLISHED PAPERS / SUBMITTED MANUSCRIPTS

Paper 1. PRICE, G.J. 2005 (2004)a. Fossil bandicoots (Marsupialia,

Peramelidae) and environmental change during the Pleistocene on the

Darling Downs, southeastern Queensland, Australia. Journal of Systematic

Palaeontology. 2: 347-356.

This chapter documents the geographic sampling area of the Pleistocene

Kings Creek catchment. Additionally, late Pleistocene Darling Downs

climates and habitats are interpreted based on fossil bandicoot

assemblages.

Contribution of authors

I collected, prepared and identified most of the material that was examined in

this paper (with additional support from others noted in the

Acknowledgements). I also supervised labouring efforts of the volunteers

who assisted in the preparation of fossil material. Additionally, I prepared the

original and final manuscript for publication.

67

Journal of Systematic Palaeontology 2 (4): 347–356 Issued 26 January 2005

DOI: 10.1017/S1477201904001476 Printed in the United Kingdom C© The Natural History Museum

Fossil Bandicoots (Marsupialia,

Peramelidae) and environmental

change during the Pleistocene on

the Darling Downs, southeastern

Queensland, Australia

Gilbert J. PriceQueensland University of Technology, School of Natural Resource Sciences, GPO Box 2434, Brisbane,Queensland, Australia 4001

SYNOPSIS Systematic collecting from fluviatile Pleistocene fossil deposits of the Darling Downs,southeasternQueensland, Australia, has led to an increase in the region’s fossil record of bandicoots.Isoodon obesulus, Perameles bougainville and P. nasuta are reported for the first time in the DarlingDowns fossil record. Accelerator mass spectrometry 14C dates based on charcoal from bandicootfossil-bearing stratigraphic horizons indicates deposition 45–40 ka. Additional material attributed tothe recently described Darling Downs P. sobbei is also described. P. sobbei retains plesiomorphiccharacters in theupperdentition including reductionof themetaconuleonM3 and the lackofposteriorcingula on M2 and M3. Phylogenetic interpretation of dental characters suggests that P. sobbei hascloser affinities to the Pliocene P. bowensis than to any modern species. The presence of extantspeciessuchasP.bougainvilleand I. obesulusas fossilsprovidesevidence thatscrublandsandclosedwoodlandswith dense understories existed on the Darling Downs during the Pleistocene. The DarlingDowns bandicoot assemblage represents the only known fauna, fossil or modern, where I. obesulus,P.bougainvilleandP.nasutaoccursympatrically. ThePleistoceneDarlingDownsmayhavehadamoreequable climate than occurs today and a greater range of habitat niches to support such populations.The southern and western contraction of the geographical ranges of I. obesulus and P. bougainvillebetween the Pleistocene and the present was probably the result of significant environmental changethat may have involved the contraction of woodlands and expansion of grasslands. The persistenceof P. nasuta populations on the Darling Downs from the Pleistocene to the present may reflect thatspecies’ ability to adapt to a wide range of habitats.

KEY WORDS Isoodon, Perameles, non-analogue assemblage, Kings Creek catchment

E-mail:[email protected].

Contents

Introduction 348

Geography and stratigraphy 348

Materials and methods 348

Systematic palaeontology 349Supercohort Marsupialia Cuvier, 1817 349Cohort Australidelphia Szalay, 1982 349

Order Peramelemorphia Kirsch, 1968 349Family Peramelidae Gray, 1825 349Genus Isoodon Desmarest, 1817 349

Isoodon obesulus Shaw, 1797 349Genus Perameles Geoffroy, 1804 351

Perameles bougainville Quoy & Gaimard, 1824 351Perameles nasuta Geoffroy, 1804 352Perameles sobbei Price, 2002 352

Discussion 353

Acknowledgements 355

References 355

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Introduction

Palaeoenvironmental interpretations of past climates and cli-mate change are commonly based on fossil assemblages thatcontain extant species with known environmental tolerances.Such interpretations are generally based on the assumptionthat species have not undergone significant biological orphysiological change over time. It is clear that many ex-tant taxa have experienced major shifts in their geograph-ical distributions since the Late Pleistocene, indicating thattheir environmental tolerances in a particular area may havechanged (Lundelius 1983, 1989; Graham et al. 1996; Staffordet al. 1999). However, evolutionary tracking of biologicalor physiological change in extant species over time in re-sponse to environmental change, would probably result inno alteration to their Pleistocene geographical distributions(Lundelius 1983). That hypothesis is difficult to assess andmay limit the precision of palaeoenvironmental interpreta-tions that are based on extant taxa occurring as fossils, butdoes not necessarily invalidate them (Lundelius 1983).

Complications commonly occur where fossil as-semblages contain extant species that provide conflicting in-formation about past climates. Many late Pleistocene fossilassemblages are characterised by the coexistence of extantspecies that today show allopatric geographical distributions(Graham & Lundelius 1984). For example, Dyrovaty KamenCave, Russia, contains the pied lemming (Dicrostonyxgulielmi near D. torquatus), a species presently confinedto arctic tundra, as well as the steppe lemming (Laguruslagurus), an inhabitant of grasslands (Stafford et al. 1999).Those species have completely allopatric distributions today,separated by over 1000 km and they occupy distinctly dif-ferent habitats. Similar types of conflicting faunal associ-ations are common throughout Eurasia, Africa, America andAustralia (Lundelius 1983, 1989; Graham & Lundelius1984). Semken (1974) used the phrase ‘disharmonious’ todescribe those fossil associations of extant species that haveno analogue with modern communities. Non-analogue as-semblages are generally time restricted, being quite commonin Late Pleistocene deposits, but rare in Holocene deposits,suggesting that most modern biomes are Holocene in age(Lundelius 1989; Stafford et al. 1999). Non-analogue asso-ciations of fossil species that provide conflicting informationabout palaeohabitats are generally interpreted as indicatinggreater habitat diversity or patchiness and such greater di-versity may have been maintained by more equable climateswith less seasonality (Lundelius 1983, 1989). Climatic in-terpretations of non-analogue assemblages are based on theassumptions that: (i) faunas, particularly mammals, are notdirectly affected by climates, but by availability of vegetationfor food and shelter and that is, in turn, affected by climate(Graham et al. 1996) and (ii) geographical ranges of extantspecies are well known (Lundelius 1983). However, the doc-umentation of geographical distributions of extant taxa hasbeen compromised in some areas such as Australia owingto the rapid contraction and disappearance of sensitivetaxa in many areas immediately following European settle-ment. Australian examples include the contraction of therange and subsequent mainland extinction of the western-barred bandicoot (Perameles bougainville) and the absoluteextinctions of the thylacine (Thylacinus cynocephalus) andToolache wallaby (Macropus greyi: Friend & Burbidge 1995;Rounsevell & Mooney 1995; Smith 1995). In contrast,

post-European settlement and pastoral activities have ledto increases in the distributions of other species such asthe eastern grey kangaroo (M. giganteus: Poole 1995). Theaim of this paper is to discuss the taxonomy and palaeoen-vironmental significance of an assemblage of fossil bandi-coots, a group of rabbit-sized terrestrial vertebrates in thefossil record of the Pleistocene Darling Downs, southeasternQueensland, Australia.

The Darling Downs is renowned as a rich source ofPleistocene vertebrate fossils. Megafaunal species such asthe rhinoceros-sized Diprotodon and giant kangaroos, in-cluding Procoptodon and Protemnodon, are well representedin the deposits, although small-sized species remain poorlyknown. Recent systematic collecting from various DarlingDowns fossil deposits have begun to yield both megafaunaltaxa as well as small-sized taxa including land snails, frogs,skinks, agamids and small mammals (Price 2002). Amongthe more interesting discoveries were new records of Pleis-tocene bandicoots that included a new species of long-nosedbandicoot, P. sobbei (Price 2002). More recent systematiccollecting from the P. sobbei type locality (QML796) andan additional fluviatile fossil deposit (QML1396: See Fig. 1)has led to further additions to the Darling Downs Pleistocenebandicoot fossil record, including examples of species thathave modern allopatric distributions.

Geography and stratigraphy

The Darling Downs, southeastern Queensland, encompasseslow rolling hills and plains west of the Great Dividing Range.The Great Dividing Range extends along the eastern seaboardof Australia (Fig. 1) and is responsible for the extreme cli-matic regimes experienced between central and eastern coa-stal Australia. Darling Downs sediments consist of clays, siltsand sands derived from erosion of underlying Miocene basaltflows and Mesozoic sandstones (Woods 1960; Gill 1978).

The Kings Creek catchment, southern Darling Downs,contains the most abundant and extensive vertebrate fossildeposits of the region (Molnar & Kurz 1997). The mod-ern Kings Creek catchment, bounded to the north, east andsouth by the Great Dividing Range, is fed by several mainlydry or intermittent watercourses (Fig. 1). Two fossil depos-its (QML796 and QML1396) located in the Kings Creekcatchment, formed the focus for the investigation (Fig. 1).Both deposits consist of fluvially transported sediments andare interpreted as representing channel and overbank de-posits. Samples of charcoal from both deposits were sub-mitted to ANSTO = Australian Nuclear Science and Tech-nology Organisation. AMS = accelerated mass spectrometry(Lawson et al. 2000) for the purpose of AMS14C dating.The QML1396 bandicoot fossil-bearing horizon was datedto 45 150 ± 1200 years ago (OZG855). A horizon overlyingthe main bandicoot fossil-bearing horizon at QML796 wasdated to 40 000 ± 750 years ago (OZG853), thereby provid-ing a minimum age for fossil bandicoots from the deposit.

Materials and methods

Fossils were recovered from distinct stratigraphic horizonsby the removal of sediment to target smaller fossil specimens.The sediments were washed using graded sieves of 10 mmto 1 mm and small bones were sorted following similar tech-niques to those described in Andrews (1990).

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Fossil Bandicoots and environmental change 349

Figure 1 Modern Kings Creek Catchment with heights (in metres) of surrounding peaks and deposits (QML) where fossil bandicoot remainswere recovered. GDR, Great Dividing Range; KCC, Kings Creek Catchment; QML, Queensland Museum Locality.

Dental nomenclature follows Luckett (1993), where theadult unreduced cheek tooth formula of marsupials is P1−3

and M1−4 in both upper and lower dentitions. Tooth mor-phology follows Archer (1976). Higher systematics followAplin & Archer (1987). Features distinguishing Isoodon andPerameles are outlined in Smith (1972) and Archer (1978).Referred material is deposited in the Queensland Museum(QMF) under Queensland Museum Localities (QML).

Systematic palaeontology

SupercohortMARSUPIALIA Cuvier, 1817Cohort AUSTRALIDELPHIA Szalay, 1982Order PERAMELEMORPHIA Kirsch, 1968

Family PERAMELIDAE Gray, 1825Genus ISOODON Desmarest, 1817

Isoodon obesulus Shaw, 1797 (Figs 2A, B; Table 1)

REFERRED MATERIAL. QMF44548, isolated LM1;QMF44547, right dentary with RM3; Both from QML796.

DIAGNOSIS. See Lyne & Mort (1981).

DESCRIPTION.

Dentary. Deepest below M3; horizontal ramus broken anteri-orly to M1 anterior alveolus and posteriorly just past anterioredge of masseteric fossa; mental foramen small, anterovent-ral to anterior alveolus of M1; vertical ramus approximately115◦ to horizontal ramus.

LM1. Sub-rectangular in occlusal outline; talonid markedlywider than trigonid; relative heights of cuspids indetermin-

Table 1 Measurements of fossil bandicoot molar teeth fromQML796 and QML1396, Darling Downs.

Species QMF Tooth Length Ant. width Post. width

Isoodon obesulus 44548 LM1 3.34 1.80 2.35Isoodon obesulus 44547 RM3 3.78 2.27 2.29Perameles 44549 RM1 2.89 1.58 1.95bougainville

Perameles 44550 RM3 – 1.83 1.88bougainville

Perameles nasuta 44567 RM1 3.62 1.91 2.33Perameles nasuta 44568 RM1 3.43 – 2.52Perameles nasuta 44566 LM3 4.20 2.50 2.56

All measurements are in mm. Length is the anterior-posterior distance. Ant.width is the lingual–buccal distance across the trigonid. Post. width is thelingual–buccal distance across the talonid.

ate due to wear; paraconid forms anterior margin of tooth,entirely lingual to midline; metaconid posterolingual toparaconid; protoconid occupies buccal portion of trigonid,slightly anterobuccal to metaconid; entoconid lies directlyposterior to metaconid; hypoconid lies posterobuccal to pro-toconid; entoconid and hypoconid on the same transverseplane; hypoconulid prominent, posterior to entoconid; formof posthypocristid and cristid obliqua obliterated by wear;buccal surface of tooth is curved lingually with enamel ex-tending to base of crown.

RM3. Sub-rectangular in occlusal outline; trigonid andtalonid are of a similar width; metaconid is tallest cusp fol-lowed in descending order by protoconid, entoconid, para-conid, then hypoconid; paraconid just posterior to anterior

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Figure 2 Darling Downs fossil bandicoot teeth. A, Isoodon obesulus, right dentary, QMF44547, lingual view; B, buccal view; C, Peramelesbougainville, RM1, QMF44549, occlusal view; D, P. nasuta, LM3, QMF44566, occlusal view; E, P. sobbei, RM2, QMF21680, occlusal view;F, P. sobbei, LM3, QMF44569.

margin, positioned lingual to midline; metaconid directlyposterior to paraconid; metaconid and protoconid are in sametransverse plane; entoconid directly posterior to metaconid;hypoconid directly posterior to protoconid; entoconid andhypoconid are in the same transverse plane; hypoconulidreduced or absent; posthypocristid runs posterolingually toposterior base of entoconid; cristid obliqua descends antero-lingually from apex of hypoconid, curving slightly to termi-nate in the midvalley at posterobuccal base of metaconid; an-terior cingulid high on anterior face of paraconid, rounded inits lingual corner, tapering buccally to terminate at theanterobuccal base of protoconid; small buccal cingulidpresent at anterobuccal base of hypoconid; buccal surfaceof tooth curved lingually with enamel extending to base ofcrown.

REMARKS. The morphology of the Darling Downs ma-terial is well within that exhibited by extant populations(Tables 1 & 2). Isoodon obesulus is easily distinguished fromall other Isoodon species by: (i) being intermediate in its size

Table 2 Mean and observed range of measurements of modern bandicoot molar teeth.

Species Tooth Length Ant. width Post. width

Isoodon obesulus M1 3.23 (3.08–3.42) 1.81 (1.74–1.90) 2.27 (2.15–2.37)Isoodon obesulus M3 3.56 (3.38–3.80) 2.45 (2.19–2.49) 2.47 (2.27–2.56)Perameles bougainville M1 2.91 (2.79–3.03) 1.53 (1.48–1.58) 1.90 (1.85–1.95)Perameles bougainville M3 3.04 (2.94–3.14) 1.88 (1.82–1.94) 1.94 (1.86–2.02)Perameles nasuta M1 3.44 (3.25–3.64) 1.95 (1.8–2.04) 2.39 (2.24–2.53)Perameles nasuta M3 3.96 (3.82–4.23) 2.42 (2.37–2.53) 2.48 (2.40–2.58)

All measurements are means in mm, with range in parentheses. Length is the anterior–posterior distance. Ant. width is the lingual–buccaldistance across the trigonid. Post. width is the lingual–buccal distance across the talonid. Measurements of Isoodon obesulus and Peramelesnasuta teeth are based on modern comparative material within the Queensland Museum and were adapted from Freedman (1967b) forP. bougainville.

between the larger I. macourous and smaller I. auratus and(ii) possessing a wider angle of the ascending ramus (Lyne &Mort 1981).

Isoodon obesulus is generally regarded as a nocturnalspecies feeding on earth worms and other invertebrates, in-sects, fungi and subterranean plant material (Braithwaite1995). Extant populations prefer sclerophyllous woodlandswith scrubby vegetation or areas with low ground coverthat are burnt out periodically (Menkhorst & Seebeck 1990;Braithwaite 1995). Braithwaite (1995) suggested that afterfire, growing vegetation supports abundant insect food andthat forms a favourable habitat for I. obesulus.

The presence of Isoodon obesulus in the Pleistocenedeposits of the Darling Downs fills a significant spatial gapbetween extant populations from southern Australia and farnorth Queensland suggesting it had a more complete distri-bution in the past (Fig. 3). It is probable that additional sys-tematically collected Pleistocene fossil deposits north andsouth of the Darling Downs will reveal additional informa-tion about the past distribution of I. obesulus populations.

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Figure 3 Extant and sub-fossil geographical distributions of bandicoot species that occur in Darling Downs fossil deposits, with otherAustralian Pleistocene deposits where combinations of those species occurred sympatrically.

Genus PERAMELES Geoffroy, 1804

Perameles bougainville Quoy & Gaimard, 1824(Fig. 2C; Table 1)

REFERRED MATERIAL. QMF44549, isolated RM1, QML1396,King Creek; QMF44550 isolated RM3, QML796, KingCreek.

DIAGNOSIS. See Freedman (1967a).

DESCRIPTION.

RM1. Sub-rectangular in occlusal outline; talonid slightlywider than trigonid; metaconid, protoconid and entoconidsub-equal in height, followed in descending order by para-conid, then hypoconid; paraconid forms anterior margin oftooth positioned slightly lingual to midline; metaconid pos-terior and slightly lingual to paraconid; protoconid occu-pies buccal portion of tooth, slightly anterobuccal to meta-conid; entoconid conical in shape, directly posterior to meta-conid; hypoconid posterobuccal to entoconid; hypoconulidlarge at posterior base of entoconid; posthypocristid incom-plete but may be an artefact of preservation; cristid obliquadescends anterolingually from apex of hypoconid, curvingslightly buccally to terminate at posterobuccal base ofprotoconid.

RM3. Anterior portion of trigonid broken; trigonid andtalonid approximately equal in width; heights of cuspids in-

determinate due to wear, although trigonid cuspids appearto be higher than talonid cuspids; hypoconulid at posteriorbase of entoconid; posthypocristid terminates at posterobuc-cal base of entoconid. All other distinguishing characters areeither not preserved or obliterated by wear.

REMARKS. The teeth described here are morphologically andmorphometrically similar to those from extant populationsof P. bougainville (Tables 1 & 2). Perameles bougainville isdistinguished from all modern species by a combination offeatures including: (i) its small size and (ii) more equidistanttrigonid cuspids. It is similar in lower molar morphology tothe Pliocene P. bowensis (Muirhead et al. 1997), but is distin-guished from it by (i) its larger size and (ii) less equidistanttrigonid cuspids. A broken RM3 (QMF44550) is referred toP. bougainville based on its small size.

Perameles bougainville is a nocturnal species, with ex-tant populations occurring only on Bernier and Dorre Is-lands, Shark Bay, Western Australia, although it once oc-curred throughout much of southern Australia (Ashby et al.1990; Kemper 1990; Menkhorst & Seebeck 1990; Friend &Burbidge 1995: Fig. 3). Post-European extinction on themainland of Australia may be attributed to land clearance andpredation from feral species such as cats and foxes (Friend &Burbidge 1995). Extant populations are commonly associ-ated with scrub and open steppe habitats, although it wasonce found on the continent in dense scrub thickets, opensaltbush and bluebush plains and on stoney ridges bordering

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352 G. J. Price

scrubland (Friend & Burbidge 1995). It is generally regardedas a semi-arid species.

The presence of P. bougainville in the Darling DownsPleistocene extends its previously known northeastern record(Fig. 3).

Perameles nasuta Geoffroy, 1804 (Fig. 2D; Table 1)

REFERRED MATERIAL. QMF44567-8, isolated RM1s;QML796, King Creek; QMF44566 isolated LM3, QML1396,King Creek.

DIAGNOSIS. See Freedman (1967a).

DESCRIPTION.

RM1. Anterior one-third triangular, remainder sub-rectangular in occlusal outline; talonid wider than tri-gonid; protoconid tallest cusp followed in descendingorder by metaconid, paraconid, hypoconid and ento-conid; paraconid forms anterior margin of tooth, po-sitioned slightly lingual to midline; metaconid poster-olingual to paraconid; protoconid occupies buccal por-tion of trigonid, on the same transverse plane as meta-conid; entoconid directly posterior to metaconid; hypo-conid posterobuccal to protoconid; hypoconid slightly pos-terobuccal to entoconid; hypoconulid at posterobuccalbase of entoconid; posthypocristid extends from hypo-conid to midline of posterior base of entoconid; cristid obli-qua straight, descending anterolingually from hypoconid toterminate at posterolingual base of protoconid; anterior andposterior cingula absent.

RM3. Sub-rectangular in occlusal outline; trigonid andtalonid of approximately equal width; protoconid tallest cuspfollowed in descending order by metaconid, paraconid, ento-conid and hypoconid; paraconid slightly posterior to an-terior margin; metaconid slightly posterolingual to para-conid; metaconid and protoconid on same transverse plane;entoconid directly posterior to metaconid; hypoconid dir-ectly posterior to protoconid; hypoconid slightly posterior totransverse entoconid; hypoconulid at posterior base of ento-conid; posthypocristid runs posterolingual to posterobuccalbase of entoconid; cristid obliqua straight, terminating at pos-terobuccal base of metaconid; anterior cingulid low on baseof crown, tapering buccally to terminate at anterobuccal baseof crown.

REMARKS. The lower molars of P. nasuta are distinguishedfrom all other Perameles (excepting the relatively larger Plio-cene P. allinghamensis where the lower dentition is unknown)by its larger size. Perameles nasuta is most similar in size toP. gunnii but is distinguished from that species by possessinga broader anterior cingulid that results in a more rectangu-lar occlusal outline of the lower molar teeth. Lower molarsdescribed here are morphologically and morphometricallysimilar to the corresponding teeth of individuals from extantpopulations (Tables 1 & 2).

Extant populations of P. nasuta have wide ranging hab-itat tolerances, being recorded from rainforest to closed andopen woodlands, to areas with little ground cover (Lavery &Grimes 1974; Stoddart 1995).

Extant P. nasuta populations have been recorded on theDarling Downs (Van Dyck & Longmore 1991: Fig. 3).

Table 3 Measurements of referred P. sobbei uppermolar teeth from QML796, Darling Downs.

QMF Tooth Length Width

21680 RM2 3.86 –44569 LM3 4.13 3.8044570 LM3 4.08 3.9944571 LM3 3.85 –

All measurements are in mm. Length is the anterior-posteriordistance. Width is the maximum lingual–buccal distance.QMF, Queensland Museum Fossil accession code.

Perameles sobbei Price, 2002 (Figs 2E & 2F;Table 3)

REFERRED MATERIAL. QMF21680, isolated RM2;QMF44569-71, isolated LM3s; all from QML796,King Creek.

DIAGNOSIS. See Price (2002), with the addition of: (i) meta-conule on M3 reduced in comparison to similar sized species,(ii) anterobuccal and posterobuccal corners of M3 less exten-ded, (iii) anterior cingulum on M2 short, absent on M3 and(iv) posterior cingula absent on M2 and M3.

DESCRIPTION.

RM2. Sub-triangular in occlusal outline; shallow ectoflexus;metacone tallest cusp followed in descending order by St D,St B, St A, metastylar tip and paracone. Comparison ofheights of metaconule and protocone not possible as lin-gual portion of tooth broken; St A forms anterobuccal cornerof tooth; St B posterolingual to St A; paracone postero-lingual to St A and anterolingual to St B; St D directlyposterior to St B; metastylar tip posterobuccal to St D;metacone lies posterolingual to paracone, transversly pos-terolingual to St D and anterolingual to metastylar tip; pre-paracrista curves anteriorly to connect to St A; postparacristaslightly shorter in length compared to preparacrista, runsposterobuccally to connect to St B; premetacrista runs trans-versely across tooth to link metacone and St D; postmetac-rista run posterolingually to link metacone and metastylar tip;preprotocrista terminates at anterolingual base of paracone;posthypocrista terminates at postlingual base of metacone;anterior cingulum short, below and buccal to midpoint ofpreparacrista.

LM3. Triangular in occlusal outline with posterior surfaceshortest of three crown dimensions; deep ectoflexus; shal-low inflexion between protocone and metaconule; metaconetallest cusp followed in descending order by St D, St B, St A,metastylar tip, protocone and metaconule; St A forms anter-obuccal corner of tooth; St B posterolingual to St A; paraconeposterolingual to St A and anterolingual to St B; St D dir-ectly posterior to St B; metastylar tip posterobuccal to St D;metacone lies posterolingual to paracone, transversely pos-terolingual to St D and anterolingual to metastylar tip; pro-tocone lies directly lingual to paracone; metaconule greatlyreduced lying posterobuccal to protocone and anterolingualto metacone; preparacrista straight, connecting paracrista andSt A; postparacrista shorter than preparacrista and connects toparacone to St B; premetacrista short, directed anterobuccallyfrom metacone, terminating at anterolingual base of St D;postmetacrista straight, connecting metacone and metastylar

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tip; preprotocrista terminates at anterolingual base of para-cone; posthypocrista absent; anterior and posterior cingulaabsent.

REMARKS. The new upper molars described here are placed inPerameles rather than Isoodon because they possess smallermetaconules on M2 and M3 (Smith 1972), less extendedanterobuccal and posterobuccal corners on M2 and M3 andthey lack complete anterior and posterior cingula on M2 andM3. The upper molars are placed in P. sobbei based on: (i)correlation of size between lower and upper molar teeth and(ii) by being morphologically distinct from all other knownspecies of Perameles.

Perameles sobbei is distinguished from P. bowensis,P. bougainville and P. eremiana by being much larger andfrom the poorly known P. allinghamensis by its smaller size.

Perameles sobbei is most similar in size to the extantP. nasuta and P. gunnii, but differs from those species bypossessing a combination of features including: (i) smallermetaconule on M3, (ii) less extended anterobuccal and pos-terobuccal corners on M2 and M3, (iii) lacking anterior andposterior cingula on M2 and M3 and (iv) preprotocrista con-necting to the anterolingual base of paracone.

Perameles sobbei is so far restricted to the type locality(QML796), despite specific searches for it at other DarlingDowns fossil localities. Morphological variation required toinclude P. sobbei in any other species of Perameles is muchgreater than that known in any single Perameles species,fossil or extant. Therefore, P. sobbei is regarded as a validspecies rather than a highly variable population of a previ-ously recognised Perameles species.

AFFINITIES. Perameles sobbei shares a combination of ple-siomorphic and apomorphic characters with most modernPerameles species. Perameles sobbei is morphologically sim-ilar to the Pliocene P. bowensis and extant P. bougainville as itpossesses a reduced metaconule on M3, a condition regardedas plesiomorphic by Muirhead (1994) who noted the autapo-morphic trait is for the metaconule to be almost as large asthe protocone.

Perameles sobbei and P. bowensis retain the ple-siomorphic character of lacking a posterior cingulum on M2

and M3, a condition that is also exhibited in plesiomorphicdidelphoids and dasyuroids. Modern Perameles are moreapomorphic in that character, as they possess better de-veloped posterior cingula. Muirhead (1994) considered thatthat feature is partially independent to the development ofthe metaconule, as evidenced in other species of bandicoots.

Perameles sobbei and P. bowensis are the only membersof the genus where the preprotocrista connects to the anter-olingual base of the protocone, a condition that also occursin plesiomorphic dasyuroids. The apomorphic condition isexhibited by all modern Perameles where the preprotocristacontinues past the anterolingual base of the paracone andterminates below the midline of the preparacrista.

Perameles bowensis is more plesiomorphic thanP. sobbei as it exhibits poor trough development betweenSt. B and St. D in the upper molars. However, on the basisof the synapomorphic condition of the reduction of thehypoconulid on M1 and absence from M3 (Price 2002),P. sobbei and P. bowensis are regarded as sister taxa andform a sister clade to all Recent Perameles. In addition, bothspecies are regarded as being more plesiomorphic than Re-cent Perameles as they retain plesiomorphies in the upper

dentition including (i) reduced metaconule on M3, (ii) lack-ing posterior cingula on M2−3 and (iii) shorter preprotocrista;and in the lower dentition by possessing equidistant trigonidcuspids (Price 2002).

The relationship between P. sobbei and the PlioceneP. allinghamensis is unclear. P. allinghamensis is so farknown only from an isolated M2 that is markedly larger thanthe corresponding tooth of all other species of Perameles.It is unique in that it is the only member of the genus thatpossesses the apomorphic character of a complete anteriorcingulum on M2 (Archer 1978). However, the anterior cingu-lum of M2 is lower on the crown than that of all other knownPerameles, a feature considered to be plesiomorphic (Muir-head et al. 1997). In addition, the preparacrista and para-stylar corner of the crown is arranged entirely differentlyto all other known species of Perameles (Muirhead et al.1997). It is for such reasons that Archer (1978) suggestedthat additional material may indicate that P. allinghamensismay actually represent a new genus of bandicoot.

Discussion

Early species lists of Darling Downs Pleistocene vertebratefaunas are dominated by extinct megafaunal taxa such asDiprotodon, Protemnodon and Macropus titan (Bartholomai1976, 1977), with small-sized forms such as bandicoots be-ing overlooked. However, since systematic collecting com-menced on the Darling Downs fossil deposits in 1997, extens-ive faunas containing small-sized taxa have been collectedthat include more samples of extant species (Molnar & Kurz1997; Price 2002). This paper extends those results with theextant species Isoodon obesulus, Perameles bougainville andP. nasuta being recognised in the Darling Downs Pleistocenefossil record for the first time.

Isoodon macrourus remains absent in the DarlingDowns fossil record despite the occurrence of extant popula-tions in the region (Van Dyck & Longmore 1991). Its absencein the Darling Downs fossil record may be explained by threehypotheses: (i) suitable habitat to support its populations waslacking on the Darling Downs during the Pleistocene; (ii) itwas out-competed for resources by other species such asI. obseulus that share a similar ecology or (iii) it occurredbut has not been sampled. Extant I. macrourus has a similardistribution to P. nasuta (Gordon et al. 1990) and both spe-cies occur in a wide variety of habitats. Hence, I. macrourusmight be expected to have occurred with P. nasuta in theDarling Downs fossil deposits. Extant I. macrourus andI. obesulus populations occur sympatrically in far northQueensland, possibly ruling out the competitive exclusionhypothesis. However, Gordon & Hulbert (1989) suggestedthat when some bandicoot species occur in areas of sympatry,habitat utilisation may be slightly different from those areaswhere they occur allopatrically. Regardless, the favoured hy-pothesis is that I. macrourus was missed during sampling.

Previous Darling Downs palaeoenvironmental analyseshave been based on interpreted ecologies of extinct mega-fauna. Previous investigations have suggested that the Pleis-tocene Darling Downs was composed of expansive grass-lands, as inferred by the wide range of grazing species, al-though some woodlands must have existed to support less di-verse populations of browsing taxa (Bartholomai 1973, 1976;Archer 1978; Molnar & Kurz 1997). Creeks and watercoursesmay have been larger in order to support the populations

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354 G. J. Price

of crocodiles that are represented in the fossil deposits(Molnar & Kurz 1997). Recently recovered small-sizedfossil taxa are beginning to demonstrate that Darling Downspalaeoenvironments were more complex than originallythought (Price 2003; Price & Sobbe 2003) and the value ofusing small-sized taxa in reconstructing past environmentsis increasingly being documented (Brothwell & Jones 1978;Andrews 1990; Vigne & Valladas 1996).

Extant species that occur in fossil assemblages forma rational basis for palaeoenvironmental reconstructions(Lundelius 1983). Interpreted ecologies of fossil bandicoottaxa drawn by analogy with extant bandicoot populations al-low additional palaeoenvironmental inferences to be madeabout the Darling Downs Pleistocene environments. In thecase of the Darling Downs, investigations of small-sized taxasuch as bandicoots are particularly important because theyonce occurred sympatrically with now extinct megafauna. Inthe light of the on-going controversy over the timing andcauses of Australian megafauna extinctions (Choquenot &Bowman 1998; Miller et al. 1999; Field & Fullager 2001;Roberts et al. 2001a, b; Brook & Bowman 2002) studies ofsmall-sized taxa and habitat change may elucidate causes formegafaunal decline on the Darling Downs.

The occurrence of P. nasuta in the Darling Downs fossilrecord is of little palaeoenvironmental significance becausethe species is known from a wide range of varying habitats.However, the fossil record of species that have more criticalenvironmental preferences such as I. obesulus, provides evid-ence that sclerophyllous woodlands and forests with denseunderstory vegetation were significant on the PleistoceneDarling Downs. Periodic Pleistocene fires may have createdmosaics of habitat suitable to sustain I. obesulus populationson the Darling Downs. Scrubby thicketed areas may alsohave existed to support populations of P. bougainville.

Comparison of the Darling Downs fossil bandicoot as-semblages to the geographical distribution of both mod-ern and fossil bandicoot assemblages where I. obesulus,P. bougainville and P. nasuta co-exist, suggests that theDarling Downs assemblage is unique. The geographical dis-tributions of extant populations of I. obesulus and P. nasutaoverlap in southeastern Australia and in far north Queensland(Fig. 3). Similarly, I. obesulus and P. nasuta occur sympatric-ally in Pleistocene fossil assemblages of the Texas Cavesfaunas, southeastern Queensland (Archer 1978), CathedralCave, central New South Wales (Dawson & Augee 1997) and,possibly, Cement Mills, southeastern Queensland (Bartho-lomai 1977: Fig. 3). Pre-European settlement, extant andsub-fossil populations of I. obesulus and P. bougainville over-lapped in southern South Australia and southwestern WesternAustralia (Fig. 3). Pleistocene fossil assemblages containingsympatric associations of those two species have been recor-ded from Victoria Cave and Henschke Fossil Cave, south-eastern South Australia (Smith 1972; Pledge 1990), SetonRock Shelter, Kangaroo Island (Hope et al. 1977) and Mam-moth Cave and Devil’s Lair, southwestern Western Australia(Merilees 1965; Dortch & Merrilees 1971: Fig. 3). Similarly,prior to European settlement, the geographical distributionof extant populations of P. bougainville and P. nasuta over-lapped slightly in southeastern New South Wales. On theDarling Downs, P. bougainville and P. nasuta are the onlybandicoot taxa represented at QML1396. However, thosetwo species, plus I. obesulus and P. sobbei, were collectedfrom the same stratigraphic horizon at QML796. Hence, theQML796 fossil bandicoot assemblage represents the only

fauna, fossil or modern, where I. obesulus, P. bougainvilleand P. nasuta are known to have occurred sympatrically.Although there are no modern analogues to explain such adiverse assemblage, the dynamic processes involved in theaccumulation of fossil assemblages must be fully understoodbefore palaeoenvironmental interpretations can be made. Hy-potheses to explain the accumulation of the QML796 include:(i) the Kings Creek catchment sampled a wide geographicalarea and possibly several habitats resulting in a spatiallymixed assemblage; (ii) fossil material was reworked fromolder to younger units resulting in a temporally mixed as-semblage; or (iii) a mosaic of habitats was present during thePleistocene to support more diverse bandicoot populationsthan today.

Documentation of the geographical area sampled in pa-laeoecological studies of fossil vertebrate deposits is rarelyattempted, primarily because it is commonly difficult orimpossible to determine the precise geographical extentrepresented by samples. The geographical extent of pa-laeodrainages is commonly poorly constrained, hence fossilassemblages in fluvial settings may contain geographic-ally mixed assemblages. However, the modern Kings Creekcatchment suggests a relatively small sampling area (Fig. 1).With relatively low rates of erosion and uplift since the latePleistocene, the Pleistocene Kings Creek catchment is un-likely to have been significantly larger than present and theupstream portion of the catchment is bounded to the north,east and south by the Great Dividing Range, which actsas a regional divide. Hence, it is highly unlikely that theKings Creek fossil deposits represent accumulations of ma-terial from geographical areas outside the immediate moderncatchment area. Therefore, hypothesis 1 is rejected. In addi-tion, while the bandicoot fossil assemblage is representedby disarticulated material, the lack of abrasive markings androunding of edges of bone indicate that reworking is minimal.Hence, hypothesis 2 is also rejected. The favoured hypothesisexplaining the Kings Creek bandicoot assemblages is that amosaic of suitable habitats was present in the PleistoceneKings Creek catchment.

The occurrences of non-analogue assemblages of fossiltaxa, such as the Darling Downs Pleistocene bandicoot taxa,can be interpreted to suggest that past climates were moreequable than at present and a greater range of habitat nicheswere available (Lundelius 1983, 1989; Graham & Lundelius1984). A more equable climate may be achieved when anenvironment has a lower temperature and lower evaporationrate resulting in increased moisture and that would result ina less extreme environment throughout the year (Lundelius1983). A climatic regime such as that may have operated onthe Darling Downs during the Pleistocene such that it couldsupport sympatric populations of I. obesulus, P. bougainvilleand P. nasuta.

The relationship between fossil and extant populationsof I. obesulus, P. bougainville and P. nasuta on the DarlingDowns is similar to that for certain Pleistocene faunas ofsouthern Africa, where Pleistocene deposits contain severalspecies that do not occur in those regions today, althoughthey do occur sympatrically in other parts of Africa (Klein1975). Lundelius (1989) recognised that those African fossilmammal assemblages are not ‘disharmonious’ assembl-ages in the sense that the extant species populations aretotally allopatric, but that they indicate that environmentalchange must have altered the distribution of those populationssignificantly since the Pleistocene. Significant environmental

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change is also likely to be responsible for the changes inthe geographical distributions of Darling Downs bandicoots.Contraction of woodlands and scrublands and expansion ofgrasslands would probably have resulted in less suitable hab-itat for bandicoots in general. Habitat change was clearlydetrimental to I. obesulus and P. bougainville populations,resulting in the contraction of their geographical distribu-tions. The persistence of P. nasuta populations on the DarlingDowns from the Pleistocene to the present is likely to be at-tributable to that species’ ability to occupy a wide range ofhabitats.

Extinction of the megafauna during the late Pleisto-cene may also be associated with environmental changeon the Darling Downs. Whether that environmental changewas due to the effects of anthropogenic modification of thelandscape through the over-use of land management prac-tices such as burning (Jones 1969), or natural contraction ofwoodlands and scrublands through aridification during theonset of the last glacial maximum, is unknown. Burning ofthe Pleistocene Darling Downs landscape by humans couldhave indirectly created mosaics of suitable habitat to supportI. obesulus populations, but may have been detrimental tothe persistence of the megafauna. However, while there isa temporal overlap in the age of the Darling Downs fossildeposits (45–40 ka) and the arrival of the first humans inAustralia (∼ 56 ± 4 ka: Roberts et al. 1994; Thorne et al.1999), there is no evidence of humans on the Darling Downsbefore 12 ka (Gill 1978). Clearly, significant environmentalchange occurred on the Darling Downs some time during thelate Pleistocene resulting in both absolute and regional ex-tinctions of several species. Only through additional studiesof Darling Downs palaeoenvironments will hypotheses aboutenvironmental change and species extinction be further con-strained.

Acknowledgements

I thank Gregg Webb and Bernie Cooke for helpful com-ments and discussions on earlier drafts of this manuscript.Scott Hocknull and Brendan Brooke are thanked for help-ful discussions on various aspects of Darling Downs pa-laeoenvironments. Discussions with Alex Baynes stimulatedthe investigation of non-analogue faunas from the Pleisto-cene Darling Downs. Ricky Bell, Phillip Colquhon, LukeShipton, Matthew Ng, Joanne Wilkinson, Trevor Sutton andIan, Diane and Amy Sobbe provided much needed supportand assistance in the collection and preparation of fossil ma-terial. Andrew Amey provided access to modern comparativematerial in the Queensland Museum. Desmond and JenniferPrice are thanked for their continued support. AMS14C dat-ing of the study at ANSTO was supported by grants fromAINSE (Grant nos: 02/013 & 03/123). This work was fun-ded in part by both the Queensland University of Technologyand the Queensland Museum.

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Paper 2. PRICE, G.J., TYLER, M.J. & COOKE, B.N. 2005. Pleistocene frogs from

the Darling Downs, southeastern Queensland, Australia, and their

palaeonenvironmental significance. Alcheringa 29: 171-182.

Late Pleistocene Darling Downs climates and habitats are interpreted based

on fossil frog assemblages. Potential taphonomic biases are also identified.


I collected, prepared and identified most of the material that was

documented in this paper (with additional support from others noted in the

Acknowledgements). I also supervised the labouring efforts of the volunteers

who assisted in the preparation of fossil material. Additionally, I prepared the

original and final manuscript for publication.

Michael J. Tyler confirmed my original identifications of fossil material and

provided comments on a draft of the manuscript.

Bernard N. Cooke provided material from two of the four localities

mentioned in the manuscript and contributed to the discussion.

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Paper 3. PRICE, G.J. & SOBBE, I.H. 2005. Pleistocene palaeoecology and



This chapter presents a detailed stratigraphic, sedimentologic, taphonomic

and palaeoecologic analysis of the late Pleistocene Darling Downs fossil

deposit at site QML1396. It represents the first of my broader excavations of

the dated faunas, including the descriptions of over 40 taxa, and provides the

first palaeoecological interpretations from this study that bear on megafaunal

extinction.



this paper (including all non-megafaunal taxa, with additional support from

others noted in the Acknowledgements). I also supervised the laboring

efforts of the volunteers who assisted in the preparation of the fossil material.

I measured stratigraphic sections, collected sediment samples, and carried

out grain size analyses. I conducted all taphonomic analyses and

subsequent palaeoecologic analyses. I prepared grants for funding the

radiocarbon dating component of the study. Additionally, I prepared the

original and final manuscripts for publication.

Ian H. Sobbe assisted in the collection, preparation, identification of

megafauna taxa, and interpretation of formational processes of the deposit.

93

PLEISTOCENE PALAEOECOLOGY AND ENVIRONMENTAL CHANGE ON THEDARLING DOWNS, SOUTHEASTERN QUEENSLAND, AUSTRALIA.

GILBERT J. PRICE AND IAN H. SOBBE

Price, G.J. & Sobbe, I.H. 2005 05 31: Pleistocene palaeoecology and environmental changeon the Darling Downs, southeastern Queensland, Australia. Memoirs of the QueenslandMuseum 51(1): 171-201. Brisbane. ISSN 0079-8835.

A diverse Pleistocene fossil assemblage was recovered from a site (QML1396)exposed in the southern banks of Kings Creek, Darling Downs, southeasternQueensland. The site includes both high-energy lateral channel deposits andlow-energy vertical accretion deposits. The basal fossil-bearing unit is laterallyextensive, fines upward and its geometry and sedimentary structures suggestdeposition within a main channel. The coarse channel fill passes upward intooverbank levee deposits made up of lenticular sandy-shelly strata alternating withmuds. Several taphonomic biases relating to preservation of different faunal groupsand skeletal elements was discerned. Biases may be related to fluvial sorting of theassemblage, but causes for differences between the preservation and accumulationof mammal versus non-mammal terrestrial vertebrates remain unclear. In general,the vertebrate material was accumulated and transported into the deposit from thesurrounding proximal floodplain. The assemblage is composed of 44 speciesincluding molluscs, teleosts, anurans, chelids, squamates, and small and large-sizedmammals. Palaeoenvironmental analysis suggests that a mosaic of habitats,including vine thickets, scrublands, open sclerophyllous woodlands interspersedwith sparse grassy understories, and open grasslands, were present on thefloodplain during the late Pleistocene. From sedimentological and ecological data,it is evident that increasing aridity during the late Pleistocene led to woodland andvine thicket habitat contraction, and grassland expansion on the floodplain. Atpresent, there is no evidence to support the suggestion that the retraction of latePleistocene Darling Downs habitats was due to anthropogenic factors.�Pleistocene, Darling Downs, Kings Creek catchment, taphonomy,sedimentology, habitat change, megafauna.

Gilbert J. Price, Queensland University of Technology, School of Natural ResourceScience, GPO Box 2434, Brisbane, 4001, Australia. Ian. H. Sobbe, M/S 422,Clifton, 4361, Australia. 1 August 2004.

The Darling Downs, southeastern Queensland,contains some of the most extensive andsignificant Pleistocene megafauna deposits inAustralia. Molnar & Kurz (1997) recognisedmore than 50 specific Darling Downs localitieswhere fossil material has been collected. Specieslists are dominated by large-sized taxa such asDiprotodon spp. , Macropus t i tan , andProtemnodon spp. (Bartholomai, 1976; Molnar& Kurz, 1997). More recently, Roberts et al.(2001a) suggested that some Darling Downsfossil deposits are among the youngest depositsknown to contain megafauna remains. AsPleistocene fossils have been known from theDarling Downs since the 1840’s (Owen, 1877a),i t is general ly assumed that thepalaeoenvironmental record is well established.Darling Downs palaeoenvironments have beeninterpreted as consisting of vast grasslands andwoodlands, as indicated by an abundant and

diverse range of grazing and browsingmegafauna species preserved in the deposits(Bartholomai, 1973; 1976; Archer, 1978; Molnar& Kurz, 1997). However, Molnar & Kurz (1997)recognised a collecting bias towards large-sizedspecies suggested that smaller-sized taxa havegenerally been overlooked. Additionally, therehave been few attempts to documentsedimentologic and stratigraphic aspects of thePleistocene deposits of the region. Macintosh(1967), Gill (1978), and Sobbe (1990) providedlimited stratigraphies for sections along creeksfrom the southern Darling Downs, introducingthe terms ‘Toolburra silt’, ‘Talgai pedoderm’ and‘Ellinthorpe clay’. However, those names havenot seen subsequent use and are not consideredvalid stratigraphic units (Molnar & Kurz, 1997).Taphonomic aspects of the deposits are alsolargely unknown. Molnar et al. (1999) reported adeposit that contained articulated remains of

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megafauna taxa, but noted that articulation offossil skeletal material was relatively uncommonin the region. Collectively, palaeonvironmentalinterpretations of the region are limited owing tothe poor understanding of stratigraphic,sedimentologic and taphonomic aspects of thedeposits, as well as past collecting biases thathave focused on the recovery of large-sized taxa.

Recent systematic collecting of a deposit (siteQML1396) from the Darling Downs targeted therecovery of both large and small-sized taxa.Consequently, a comprehensive faunalassemblage has been uncovered. Typical DarlingDowns megafauna taxa are represented, as wellas an extensive small-sized fauna that includes adiverse range of molluscs, teleosts, anurans,chelids, squamates, and small and large-sizedmammals. Such assemblages are beginning todemonstrate that Pleistocene Darling Downspalaeoenvironments were much more complexthan previously thought (Price, 2002; Price,2004; Price et al., in press). The aim of the presentpaper is to describe a multidisciplinary approachintegrating sedimentologic and taphonomicinformation, as well as ecological informationobtained from mammals and non-mammals thatoccur in the deposit. The combined data sets

allow a better understanding of Pleistocenepalaeoenvironments and possible climate changein the region. In light of the ongoing debate overthe causes and timing of Australian megafaunaPleistocene extinctions (e.g. Field & Fullager,2001; Roberts et al. 2001a, b; Brook & Bowman,2002; 2004; Barnosky et al., 2004; Johnson &Prideaux, 2004; Wroe, 2004), studies ofPleistocene palaeoenvironments may provideimportant information that could aid inelucidating the causes of faunal change.

SETTING

The Darling Downs, southeastern Queensland,encompasses low rolling hills and plains west ofthe Great Dividing Range. Fluvial sediments ofthe region consist of clays, silts and sands that aregenerally derived from the erosion of Mesozoicsandstones (Gill, 1978) and Miocene basalts ofthe Great Dividing Range (Woods, 1966). SiteQML1396 is exposed laterally over 70 metres inthe southern bank of Kings Creek, southernDarling Downs (Fig. 1). The modern KingsCreek catchment, bounded to the north, east andsouth by the Great Dividing Range, is fed byseveral mainly dry or intermittent watercourses(Fig. 1), resulting in a relatively small geographic

172 MEMOIRS OF THE QUEENSLAND MUSEUM

FIG. 1. Modern Kings Creek Catchment with heights (metres) of surrounding peaks, and the current study area,QML1396 (GDR: Great Dividing Range; KCC: Kings Creek Catchment).

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sampling area. Considering relatively low ratesof erosion and uplift since the late Pleistocene, itis unlikely that the Pleistocene Kings Creekcatchment was markedly larger than present(Price, 2004). Therefore, it is unlikely thatmaterial from QML1396 was subjected to longdistance fluvial transport from a significantlylarger catchment.

METHODS

SEDIMENTOLOGY. A section was measuredrepresenting the entire depositional sequenceexposed in the creek bank. Stratigraphic horizonswere distinguished on the basis of lithologicalcriteria. Sediment samples were collected fromeach stratigraphic horizon for the purpose ofgrain size analysis. The sediment samples weredisaggregated by applying alternating cycles ofbleach and detergent. Disaggregated sedimentswere dried and sieved according to Wentworthsize classes (-2 to +4 phi; Wentworth, 1922).Differentiation and identification of calcretefollowed Arakel (1982).

One unit (Horizon D; Fig. 2) containedabundant lenses of the freshwater gastropod,Thiara (Plot iopsis) balonnensis . Theorientations of 100 gastropods from one suchlense were measured to determine whetherfluvial transport acted on the gastropods ininfluencing their final orientations. The anglewas measured between north and the spire of theshell (long direction).

TAPHONOMY. Cranial and post-cranialelements from horizons B and D formed the basisfor the taphonomic study. The units of elementrepresentation were NISP (number of identifiedspecimens), MNI (minimum number ofindividuals- as determined by counting the mostabundant element referable to a particular speciesrepresented in the sample), and MNE (minimumnumber of elements) (following Andrews, 1990).For vertebrates, calculation of MNI was based onmaxillary and dentary remains, except in the caseof fish, frogs, turtles and some squamates wherevertebrae, pelvi, shell fragments and osteodermswere used respectively.

Several indices were used to characterise anddescribe the taphonomic features of theassemblage based on the skeletal remains of largeand small mammals, as well as squamates.Relative abundance. Relative abundance of eachskeletal element was calculated following theequation:

Ri= Ni � 100 / (MNI)Ei (1)

following Andrews (1990), where R = relativeabundance of element i, n= minimum number ofelement i, MNI = minimum number ofindividuals, and E = expected number of elementi in the skeleton. The relative abundance equationallows the comparison of different skeletalelements that occur in varied proportions inmammal or squamate skeletons. Determinationof E was based on modern comparative skeletonsfor mammals and follows Greer (1989) forsquamates.

% Post-crania to crania. The percentage ofpost-crania to crania follows Andrews (1990).The number of post cranial elements (femur,tibia, humerus, radius and ulna [n=10]) arecompared to cranial elements (dentary, maxillaand molars [n=16 for murids, 20 for marsupials, 4for squamates]). As the ratio of post crania tocrania is not 1:1, the post crania and crania arecorrected by 10/16 for murids, 10/20 formarsupials, and 10/4 for squamates, to matchnumbers of skeletal elements.

DARLING DOWNS PALAEOECOLOGY 173

FIG. 2. Measured section of QML1396.

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% Distal element loss. Distalelement loss was measured bycomparing the number of distallimbs (tibia and radii) to proximallimbs (femura and humeri). Theratio measures preferential loss ofdistal limbs.% Fore limb element loss. Limbelement loss was measured bycomparing the number of fore limbbones (humeri and radii) to hindlimb bones (femora and tibiae).The rat io measures anypreferential loss of fore limbs.% Molar tooth loss. Molar toothloss was measured by comparingthe number of isolated molars inthe sample to the number ofavailable alveoli spaces in thedentaries or maxillae. Values>100% indicates the loss ordestruct ion of dentar ies ormaxillae (Andrews, 1990).% Relative loss of molar tooth sites. Relative lossof molar tooth sites was calculated by comparingthe actual number of tooth sites in the sample(regardless of whether they contain teeth or not)to the theoretical number of molar tooth sitesassuming that there was no breakage. Relativeloss of molar tooth sites was used as anindependent check for cranial breakage (Kos,2003).Cranial modifications. The cranial breakagepatterns of squamates and mammals wereidentified within the deposit following Andrews(1990; Figs 3 & 4). The percentage ofrepresentation of each pattern was calculated toattempt to distinguish any differences betweenlarge and small-sized mammals, as well asbetween agamid and scincid lizards.Breakage of post-crania. Identification ofbreakage patterns of major post-cranial limbbones (humeri, femora, ulnae and tibiae) followsAndrews (1990). Broken limb bones were scoredas to whether the represented proximal, shaft, ordistal portions.Comparison to “Voorhies Groups”. Theexperimental work of Voorhies (1969) andDodson (1973), on hydraulic dispersivemechanisms for mammal bones, forms acomparative framework for explaining thedispersal of skeletal elements in the fossil record.Their studies documented transportability ofdifferent skeletal elements at constant rates of

water flow, and concluded that different skeletalelements disperse at different rates in relation tostream flow velocity. Differences in the dispersalpotential of skeletal elements reflect the densityand shape of the elements. Relative abundance ofelements from the QML1396 assemblage werecompared to the published results for skeletalelement transportability in hydraulic systems.

FAUNA. Fossils were recovered by in situcollecting and sieving of sediment specifically totarget smaller specimens. Fossil material wasgenerally restricted to Horizons B and D (Fig. 2).All fossil material collected was labeledaccording to the stratigraphic horizon where itwas collected. Sediments were washed usinggraded sieves of 10mm to 1mm. Approximately700kgs of sediment were processed fromHorizon D, and 200kgs of sediment wereprocessed from Horizon B. The disparity incollecting efforts between Horizons D and Breflects the position of Horizon B below thepresent water table. Collecting of Horizon B wasgenerally possible only during droughtconditions. Most material was collected fromHorizon B in November and December 2002.

Descriptions of the fossil fauna have beenlimited to diagnostic features in most cases.Molluscan shell terminology follows Smith andKershaw (1979). Squamate cranial morphologyterminology follows Withers and O’Shea (1993).Marsupial dental nomenclature follows Luckett(1993), where the adult unreduced cheek tooth


FIG. 3. Mammal cranial breakage categories from the QML1396assemblage (shaded areas indicates the preserved portions). Refer totable 5 for definition of the breakage categories.

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formula is P1-3 and M1-4 in both upper andlower dentitions. Marsupial dental morphologyfollows Archer (1976). Higher systematicsfollows Beesley et al. (1998) for molluscs,Glasby et al. (1993) for amphibians and reptiles,and Aplin and Archer (1987) for mammals. Allmaterial is deposited at the Queensland Museum(QMF: Queensland Museum Fossil; QML:Queensland Museum Locality).

DATING. Samples of charcoal and freshwaterbivalves (Velesunio ambiguus) were submitted toANSTO (Australia Nuclear Science andTechnology Organisation; Lawson et al., 2000)for the purpose of AMS14C dating. Onlycomplete, conjoined bivalves were submitted fordating. Con-joined, apparently well-preservedbivalves are unlikely to have been reworked incomparison to disarticulated or fragmentary shellremains.

RESULTS

SEDIMENTOLOGY. The entire deposit ischaracterised by a fining-upwards sequence (Fig.2). The section is comprised of: 1) grey-white toblack clays; 2) in-situ mottled calcretes; 3) ironnodules; 4) quartz sand in channel fills; 5) basalt,calcrete and sandstone pebbles and cobbles (pre-dominantly in coarser fills); and 6) invertebrateand vertebrate fossils (Table 1). Freshwaterbivalves (Velesunio ambiguus and Corbicula(Corbiculina) australis) and thiarid gastropods(Thiaria (Plotiopsis) balonnensis) are moreabundant in coarser-grained horizons such asHorizon B and D, than fine-grained horizons.Vertebrate fossil material is generally restrictedto Horizons B and D.

Horizon B exhibits the largest grain sizes (Fig.2, Table 1). The horizon is laterally extensive,being recorded over approximately 70 metres.The majority of the lower portion of Horizon B is


Horizon(height)

Fill type Mean � Characteristics Notes

A (0-0.2m) Fine montmorilloniteclay 2.65 crudely horizontal bedding; poorly

sorted, srtrongly fine skewed grainspebbles to 20mm rare; shelly marterialrare; vertebrate material rare

B(0.2-0.6m) coarse grain fill bed -0.78-0.19 fining upwards sequence; poorly sorted;finely skewed grains

Freshwater molluscs abundant;vertebrate material abundant; roundedbasalt, calcrete and sandstone pebblesand cobbles abundant

C(0.6-1.7m) brown-grey clay 1.7crudely horizontal bedding, poorly tovery poorly sorted; strongly finelyskewed grains

Mollusc shell rare; vertebrate materialrare

D (1.7-2.6m) coarse to fine-sizedquartz sand beds 0.6-2.0

Sand beds 3cm to 10cm thick overlainby laterally discontinuous horizontaland sloping shelly lenses 2-10cm thick;shell beds with desiccation cracks, infilled by fine clays; very poorly sorted,fine skewed grains

Freshwater gastropods and small bi-valves common, large-sized bivalvesrare; polymodal orientation of Thiara(Plotiopsis) balonnensis gastropods(Fig. 5); vertebrate material abundant;shell and vertebrate fossil material com-monly cemented by calcrete

E (2.6-3.1m) brown clay 2.53 Crudely horizontal bedding; poorlysorted, strongly fine skewed grains


F (3.1-7.2m) brown clay 1.88

Crudely horizontal bedding; in-situ,mottled, grey-white calcrete; ironnodules to 5mm diameter present;poorly sorted, strongly fine skewedgrains


G (7.2-7.7m) black clay 2.0Crudely horizontal bedding; iron oxidesto 5mm diameter present; poorly sorted,strongly fine skewed grains

Organic rich clay; mollusc shell rare;vertebrate material rare

H (7.7-8.3m) grey-white clay 2.8 Crudely horizontal bedding; poorlysorted, strongly fine skewed grains


I (8.3-8.8mm) grey-white clay 3.0Crudely horizontal bedding; iron oxidesto 5mm diameter present; poorly sorted,strongly fine skewed grains


J (8.8-9.5m) grey clay 2.4 Crudely horizontal bedding; poorlysorted, strongly fine skewed grains


K (9.5-10.2m) black clay 2.98 Moderately sorted, strongly fine skewedgrains

Organic rich, likely altered by modernagriculture

TABLE 1. Description of stratigraphic horizons at QML1396.

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below the modern watertable. Large-sizedbivalves (Velesunio ambiguus) are moreabundant in Horizon B than in Horizon D.

Horizon D is represented by a series of coarseto fine quartz sand beds that are overlain bylaterally discontinuous horizontal and slopingshelly lenses (Fig. 2, Table 1). Desiccation crackswithin the shelly lenses are filled with fine clay. Arose diagram plot of the orientations offreshwater gastropods (Thiaria (Plotiopsis)balonnensis) indicates a polymodal distribution(Fig. 5).

In-situ, non-reworked mottled calcretes occurin Horizon F. Iron oxide nodules were alsopresent within that horizon, as well as Horizons Gand I. Few sedimentary structures other thancrudely horizontal bedding were observed withinother stratigraphic horizons (Fig. 2, Table 1).

TAPHONOMY. Vertebrate fossil material wasgenerally restricted to Horizons B and D. Fossilmaterial from other horizons is poorly preserved.Hence, the following taphonomic observationsare based on fossil material from Horizons B andD. Additionally, a large number of unidentifiablebone fragments were collected from the mainfossiliferous horizons. Few meaningful datacould be obtained from those fragments, hence,the taphonomic component was based solely onidentifiable elements.


Horizon D Horizon B

Species NISP MNI NISP MNI

Velesunio ambiguus 10+ 5+ 20+ 10+

Corbicula (Cobiculina) australis 100+ 100+ 50+ 50+

Thiara (Plotiopsis) balonnensis 1000+ 1000+ 50+ 50+

Gyraulus gilberti* 249 249 0 0

Coencharopa sp.* 9 9 0 0

Gyrocochlea sp. 1* 35 35 0 0

Gyrocochlea sp. 2* 5 5 0 0

Austrocuccinea sp.* 1 1 0 0

Xanthomelon pachystylum* 1 1 0 0

Strangesta sp.* 1 1 0 0

Saladelos sp.* 1 1 0 0

Teleost 89 1 0 0

Limnodynastes tasmaniensis 8 8 0 0

L. sp. cf. L. dumerili 3 3 0 0

?Limnodynastes 1 1 0 0

Neobatrachus sudelli 2 2 0 0

Kyarranus sp.* 1 1 0 0

chelid 4 1 0 0

Tympanocryptis “lineata”* 15 4 0 0

"Sphenomorphus group” sp. 1 19 13 0 0

“Sphenomorphus group” sp. 2 6 2 0 0

Tiliqua rugosa* 6 1 0 0

Cyclodomorphus sp.* 1 1 0 0

Varanus sp. 1 1 0 0

Megalania prisca** 4 1 0 0

elapid 14 1 0 0

Sminthopsis sp. 1 1 0 0

Dasyurus sp. 1 1 0 0

Sarcophilus sp.* 0 0 1 1

Thylacinus cynocephalus** 0 0 1 1

Perameles bougainville* 1 1 0 0

Pe. nasuta 1 1 0 0

Diprotodon sp.** 0 0 1 1

Thylacoleo carnifex** 0 0 1 1

Aepyprymnus sp. 1 1 0 0

Troposodon minor** 0 0 2 2

Macropus agilis siva** 5 2 1 1

M. titan** 1 1 5 2

Protemnodon anak** 2 1 3 1

Pr. brehus** 2 1 1 1

Pseudomys sp.* 4 2 0 0

Rattus sp. 2 1 0 0

unidentified murid 182 26 0 0

TABLE 2. Species NISP and MNI for Horizons D andB at QML1396 (* Extinct on Darling Downs; **Totally extinct).

Horizon D Horizon B

<5kgmammals

<5kgsquamates

>5kgmammals

>5kgmammals

skeletalelement n % n % n % n %

dentary 7 10.6 29 72.5 1 8.3 6 30

maxilla 7 10.6 17 42.5 4 33.3 0 0

incisor 101 76.5 na na 2 8.3 4 20

molar 97 19 na na 23 24 19 11.9

femur 11 16.7 0 0 0 0 0 0

tibia 18 27.3 0 0 0 0 0 0

pelvis 2 3 0 0 1 8.3 0 0

calcaneum 10 15.2 0 0 1 8.3 0 0

humerus 4 6.1 2 5 0 0 0 0

radius 2 3 0 0 0 0 0 0

ulna 8 12.1 0 0 0 0 0 0

ribs 6 0.9 0 0 0 0 0 0

vertebra 57 3.9 196 12.6 20 7.6 0 0

phalange 53 3.5 2 0.2 1 0.4 2 0.4

TABLE 3. MNE and expected relative abundance ofskeltal elements recovered from Horizons D & B atQML1396.

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Species representation. In terms of diversity, landsnails, frogs, squamates and small mammalsdominated the terrestrial faunal componentrepresented in the Horizon D assemblage (Fig. 6,Table 2). Large mammals were the leastrepresented size group in Horizon D, and the onlyrepresented terrestrial group in Horizon B (Fig.6).

Skeletal relative abundance. Skeletal relativeabundance was calculated for large and smallmammals, as well as squamates (Table 3). Interms of relative abundance, cranial elements ofsquamates are the most well represented elementfor the three major groups of terrestrial animals inHorizon D. However, overall, the relativeabundance of all skeletal elements suggests thatthey are underrepresented. Incisors are the mostabundant cranial element recovered for smallmammals in Horizon D, but that may reflect aprocessing bias as incisors are among the mosteasily identifiable small mammal remains(Andrews, 1990). The dentary is a relativelyrobust element and that may account for thehigher proportion of skeletal elements forsquamates and mammals in both horizons. Thereis a greater loss of squamate post-cranial remainsin comparison to mammals in Horizon D.

Small-s ized terrestr ia lver tebrates were notrecovered from Horizon B.Skeletal modif icat ions.Indices of skeletal mod-ifications (Table 4) indicatethat there is significant loss ofpost-cranial elements in eachhorizon. Horizon B iscompletely devoid of large-sized mammal limb boneelements. For Horizon Dmammals there was a slightloss of proximal l imbs(femora and humeri) incomparison to distal limbs(tibiae and radii). Additionally,there was a significant loss offorelimb elements in com-parison to hind limbs. Reasonsfor the loss of different limbelements remain unclear, butmay simply be the result ofusing stat is t ical ly smallnumbers for comparison.Indices for the loss of molarteeth and molar tooth sitesindicate the loss or destruction

of dentaries or maxillae for mammals within eachmain fossiliferous horizons (Table 4).Breakage of crania. There were no completemammal skulls or dentaries recovered from thedeposit (Table 5). Mammal dentary breakageappears slightly greater for Horizon D thanHorizon B. A high proportion of broken maxillaeretained only a small portion of the zygomaticarch in Horizon D.


FIG. 4. Squamate cranial breakage categories from the QML1396assemblage (shaded areas indicates the preserved portions). Refer to table 6for definition of the breakage categories.

skeletalmodification

Horizon D Horizon B

<5kgmammals

< 5kgsquamates

>5kgmammals

>5kgmammals

% post-craniato crania 24.2 17 0 0

% distalelement loss 133.3 0 0 0

% fore limbloss 41.4 0 0 0

% molartooth loss 741 na

noavailable

toothspaces

150

% relativeloss of molartooth sites

275 na 160 109

TABLE 4. Skeletal modifications for arbitary faunalgroups from QML1396

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There also were no complete squamate skullsor dentaries preserved (Table 6). Reasonablycomplete dentaries are equally abundant in bothagamids and scincids. However, particularbreakage patterns appear to be exclusive to eachsquamate family (Table 6). For agamids, thecentral portion of the dentary and central toanterior portions of the maxilla are preserved; forskinks, the majority of the dentary and central toposterior portions of the maxilla are preserved.Overall, scincid dentaries are more completelypreserved than those of agamids. However, areverse trend exists for the maxillae, where agreater portion are preserved inagamids than scincids (Table 6).

Breakage of post crania. Therewere no complete major limbbones (i.e. humeri, ulnae, femora,tibiae) preserved in the deposit(Table 7). Additionally, majorlimb bones were mostly restrictedto small-sized mammals fromHorizon D. Most broken limbbones have transverse fracturesperpendicular to the bone surfaceand indicate post-mortemfracturing of dry or fossilised bone(Johnston, 1985). Additionally,the broken ends of the limb bonesdo not appear to be significantly

rounded or abraded, suggesting minimalreworking or transport of fossil material.Squamates were represented by only twoproximal humeri from Horizon D. However, highnumbers of unidentifiable limb element shaftsfrom small-sized animals (n~120) could equallybe referable to either squamates or mammalpost-cranial limb bones.Comparison to “Voorhies Groups”. For HorizonD small-sized mammals, the majority of theskeletal elements comprise those that woulddisperse in the middle to late categories ofdispersal (Table 8). Additionally, the highnumber of limb bone shafts (see earlierdiscussion) would presumably fit within thatcategory of stream transportability. There was noclear trend for small-sized squamates from


FIG. 6. Comparison of MNI and NISPof terrestrial taxa from Horizons Band D at QML1396.

Breakage patternHorizon D Horizon B

<5kgmammals

> 5kgmammals

<5kgmammals

% dentary with ascendingramus mostly absent (Fig.3A)

0 - 17

% dentary with ascendingand anterior ramus mostlyabsent (Fig. 3B)

33 - 50

% dentary with anteriorramus only, lacking inferiorborder(Fig. 3C)

67 - 0

% dentray with horizontalramus only lacking inferiorborder (Fig. 3D)

0 - 33

% maxilla with most ofzygomatic missing (Fig. 3E) 100 75 -

% maxilla alveoli or toothrow only (Fig. 3F) 0 25 -

TABLE 5. Mammal cranial modifications fromQML1396 (following breakage patterns Fig. 3)

FIG. 5. Orientations of Thiara (Plotiopsis) balonnensisgastropods (n: 100) from a single shelly lense withinHorizon D at QML1396.

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Horizon D. For large-sized mammals fromHorizon D, the majority of elements comprisedthose that are progressively the last to betransported in flowing water. Horizon B isdominated by middle-late transported elements(i.e. dentaries; Table 8).

SYSTEMATIC PALAEONTOLOGY

A much abbreviated treatment of thesystematic palaeontology is given in order todocument the specific material for which taxa areassigned. The fundamental purpose of thetaxonomic work was to facilitate ecologic andassemblage information. Thus, only thediagnostic features of the material are provided,as all faunal elements are well known fossil orextant taxa. At the end of each description theprimary authority used for identification is givenin closed brackets. Two other publications dealwith the amphibians (Price et al., in press) and thebandicoots (Price, 2004).

Phylum MOLLUSCA Linnaeus, 1758Class BIVALVIA Linnaeus, 1758

Family HYRIIDAE Ortmann, 1910

Velesunio Iredale 1934Velesunio ambiguus (Philippi, 1847) (Fig. 7A)

REFERRED MATERIAL. QMF44633; QMF44651;QMF44653.

DESCRIPTION. Equivalved, length to 110mm,moderately to well inflated; shell thin to verythick; weak ridge runs posteriorly from umbone;pallial line well developed; pallial sinus absent;anterior and posterior adductor muscle scars well

developed; teeth lamellar, cardinal teeth absent;hinge moderately developed; beak cavitymoderately developed. [Lamprell & Healy,1998]

Family CORBICULIDAE Gray, 1847

Corbicula Mühfeld, 1811Corbicula (Corbiculina) Dall, 1903

Corbicula (Corbiculina) australis (Deshayes,1830)

(Fig. 7B)

REFERRED MATERIAL. QMF44628-30.

DESCRIPTION. Equivalved, length to 20mm,slightly inflated; pallial line entire but weak;anterior and posterior adductor muscle scarsweakly defined; anterior and posterior pedalretractor muscle scars hidden by overhang ofanterior and posterior teeth respectively; threecardinal teeth, and anterior and posterior lateralteeth well developed; beak cavity very deep;hinge line narrow. [Lamprell & Healy, 1998]


<5kg mammals <5kg squamates

Limb bone n % n %

humerus

complete 0 0 0 0

proximal 1 17 2 100

shaft 4 66 0 0

distal 1 17 0 0

femur

complete 0 0 0 0

proximal 7 39 0 0

shaft 0 0 0 0

distal 11 61 0 0

ulna

complete 0 0 0 0

proximal 8 73 0 0

shaft 2 18 0 0

distal 1 9 0 0

tibia

complete 0 0 0 0

proximal 0 0 0 0

shaft 3 15 0 0

distal 18 85 0 0

TABLE 7. Breakage patterns of major post craniallimb bones from Horizon D, QML1396.

Breakage pattern agamids skinkids

% dentary mostly complete (Fig. 4A) 38 43

% posterior portion of dentary only (Fig. 4B) 0 33

% anterior portion of dentary only (Fig. 4C) 0 24

% central portion of dentary only (Fig. 4D) 38 0

% central portion of dentary only, lackinginferior border (Fig. 4E) 25 0

% premaxilla and maxilla mostly complete(Fig. 4F) 22 0

% maxilla mostly complete, lackingpremaxilla (Fig. 4G) 67 0

% premaxilla only (Fig. 4H) 11 0

% posterior portion of maxilla only(Fig. 4I) 0 25

% central portion of maxilla only (Fig. 4J) 0 75

TABLE 6. Squamate cranial modifications fromHorzon D, QML1396

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Class GASTROPODA Cuvier, 1797Order SORBEOCONCHA Fischer, 1884

Family THIARIDAE Troschel, 1857

Thiara (Plotiopsis) Brot 1874Thiara (Plotiopsis) balonnensis

(Conrad, 1850)(Fig. 7C)


DESCRIPTION. Shell. Elongate, dextrallycoiled, robust, turreted, length to 30mm; 6-7whorls, carinate, spiral ridges complementedwith nodules; ovoid shaped aperture; inner lipthickened, outer lip thin. [Smith and Kershaw1979]

Order PULMONATA Cuvier, 1817Family PLANORBIDAE Rafinesque, 1815

Gyraulus Charpentier,1837Gyraulus gilberti (Dunker, 1848)

(Fig. 7D).


DESCRIPTION. Shell. Planispiral, diameter to6.29mm; 4 whorls; spire sunken; umbilicus wide;last whorl with a peripheral keel; shell sculptureconsists of fine transverse ridges; aperture keeledelongate; outer lip relatively thin and straight.[Brown, 1981]

Family RHYTIDIDAE Pilsbry, 1895

Saladelos Iredale, 1933Saladelos sp.

(Fig. 7E)

REFERRED MATERIAL. QMF44956.

DESCRIPTION. Shell planispiral, diameter to3mm; whorl count reduced, 2-3 whorls, lastwhorl capacious; spire slightly depressed; shellsculpture of fine radial ribs; umbilicus narrow;aperture ovate-lunate; lip simple. [Iredale ,1933]

Strangesta Iredale, 1933Strangesta sp.

(Fig. 7F)


DESCRIPTION. Shell. Planispiral, diameter to6.82mm; 3-4 whorls; slightly depressed spire;apical sculpture of fine to medium coiled radialribs; umbilicus narrow; aperture wide,ovate- lunate; l ip simple. [Smith andKershaw,1979]

Family CHAROPIDAE Hutton, 1884.

Coenocharopa Stanisic, 1990Coenocharopa sp.

(Fig. 7G)


DESCRIPTION. Shell. Planispiral, diameter to4.5mm; whorls coiled, last descending; apex andspire slightly elevated; apical sculpture ofprominent coiled radial ribs; post-nuclear


Relativemovement

Dodson (1973)small mammals

Voorhies (1969)large mammals

Horizon D Horizon B

<5kg mammals < 5kg squamates >5kg mammals >5kg mammals

late mandible skull,maxilla

tibiafemur,

calcania,ulna,

dentarymaxilla

humerus,vertebrae

radius

dentary,maxilla,vertebaehumerus

maxilladentarypelvi

vertebrae

dentary

middle-latecalcania,radius,ulna

mandible

middle

skulltibia-fibula,

femur,hunerus

femur,tibia

humeruspelvisradius

early-middlepelvis,

cervical and caudalvert.

ulna

early thoracic vertmaxilla vertebra

TABLE 8. Skeletal element transportability for small mammals (Dodson, 1973) and large mammals (Voorhies,1969) compared to the relative abundance of skeletal elements from Horizons B and D at QML1396 (listed indecreasing abundance). Elements higher in the Dodson (1973) and Voorhies (1969) columns were the last to betransported by moving water in flume experiments.

103

sculpture moderately spaced; umbilicus wide andU-shaped; aperture ovate-lunate; lip simple.[Stanisic, 1990]

Gyrocochlea Hedley, 1924Gyrocochlea sp. 1 and 2

(Fig. 7H)REFERRED MATERIAL. Sp. 1: QMF44590-95; Sp. 2:QMF44598-602.

DESCRIPTION. Shell planispiral, diameter to4mm; moderately tightly coiled whorls, lastdescending more rapidly; apex slightly concave;apical sculpture of fine crowded spiral cords andweakly curved radial ribs; umbilicus wide andU-shaped; aperture ovately lunate; lip simple.[Stanisic 1990]

REMARKS. Gyrococlea sp. 1 differs fromGyrococlea sp. 2 by a smoother shell sculpture,and possessing a more closed umbilicus.

Family SUCCINEIDAE Beck, 1837

Austrosuccinea Iredale, 1937Austrosuccinea sp.

(Fig. 7I)REFERRED MATERIAL. QMF44580.

DESCRIPTION. Shell elongate, dextrallycoiled; shell height 10.65mm; 4 whorls present,last whorl large; spire short; fine growth lines on

shell; aperture ovate; inner lip relatively straight,outer lip thin and straight. [Smith & Kershaw,1979]

Family CAMAENIDAE Pilsbry, 1895

Xanthomelon Martens, 1861Xanthomelon pachystylum (Pfeiffer, 1845)

(Fig. 7J)REFERRED MATERIAL. QMF44581.

DESCRIPTION. Shell subglobose, diameter to18.7mm; 4 whorls present, body whorl large;spire slightly elevated; shell sculpture relativelysmooth; anomphalous; aperture ovate lunate;outer and inner lip simple, thin. [Solem,1979]

Phylum CHORDATA Linnaeus, 1758Class REPTILIA Laurenti, 1768Order SQUAMATA Oppel, 1811

Family AGAMIDAE Hardwicke & Gray, 1827.

Tympanocryptis Peters, 1863Tympanocryptis “lineata” Peters, 1863

(Fig. 8H)REFERRED MATERIAL. QMF44198-202, maxillaryfragments; QMF44619, dentary.

DESCRIPTION. Maxilla. 4 foramen present;pleurodont teeth 2, acrodont teeth 12; 1stpleurodont tooth oritentated mesiobuccally; 2ndpleurodont tooth caniniform; maxillary suture


FIG. 7. A. Velesunio ambiguus; B. Corbicula (Corbiculina) australis; C. Thiara (Plotiopsis) balonnensis ; D.Gyraulus gilberti; E. Saladelos sp.; F. Strangesta sp.; G. Coenocharopa sp.; H. Gyrococlea sp.; I.Austrosuccinea sp.; J. Xanthomelon pachystylum.

104

anterodorsal to pleurodont teeth; dorsalmaxillary process narrow.

Dentary. Short; 3 mental foramina present;pleurodont teeth 2, acrodont teeth 12; pleurodontteeth closely positioned, 2nd pleurodont twicethe size of the 1st; acrodont teeth sub-triangularwith indistinct anterior and posterior conids;Meckel’s groove parallel to dental sulcus,narrowed anteriorly. [Hocknull, 2002]

REMARKS. Tympanocryptis l ineata isdistinguished from other members of the genusby a combination of features including: 1) its

larger size, 2) 1st pleurodont tooth orientatedmesiolabially, and 3) lower anterior hook.

Family SCINCIDAE Oppel, 1811

Skinks are the largest and most diversesquamate group in Australia (Greer, 1979;Hutchinson, 1993). Within the Scincidae, threedistinct monophyletic groups are informallyrecognised: the Egernia group, Eugongylusgroup, and Sphenomorphus group (Greer, 1979,Hutchinson, 1993). Members allied to theSphenomorphous Group and Egernia group arerepresented in the deposit.


FIG. 8. A. Fish vertebra; B. Limnodynastes tasmaniensis, left ilium; C. L. sp. cf. L. dumerili, left ilium; D.?Limnodynastes sp., right ilium; E. Neobatrachus sudelli, right ilium; F. Kyarranus sp.; G. Chelid plastronfragment; H. Tympanocryptis “lineata”, right dentary. I. “Sphenomorphus Group” sp., right dentary; J. Tiliquarugosa, osteoderm; K. Cyclodomorphus sp., left dentary; L. Varanus sp. vertebra; M. Megalania prisca,osteoderms; N. Elapid vertebra.

105

“Sphenomorphus Group” sp. 1 and 2 (sensuGreer, 1979)

(Fig. 8I)REFERRED MATERIAL. Sp. 1: QMF44620-22,QMF44654, dentaries; Sp. 2: QMF44623-25, maxillae.

DESCRIPTION. Dentary. Tooth row bears up to17 teeth or tooth loci; Meckel’s groove widelyopen along ventrolingual margin; internalseptum poorly developed; up to 6 mentalforamina present, last one postitioned about thelevel of the 12th tooth; tooth crowns not flared orthickened; lingual face of each crown vertical.[Greer, 1979]

REMARKS. Sphenomorphus Group membersare distinguished from the Egernia andEugongylus Groups by possessing a Meckel’sgroove that remains open along the length of theventrolingual margin of the dentary (Hutchinson,1993). Two distinct size classes of membersrepresenting the Sphenomorphus group wereidentified within the deposit. Hutchinson (1993)recognised that while sexual dimorphism iscommon in skinks, it is only subtle. The large sizedifference between the two size classes isconsidered here to represent distinct species.

Until the taxonomy of those two species isbetter known, their significance in PleistoceneDarling Downs will remain unclear.

“Egernia group” (sensu Greer, 1979)

Tiliqua Gray 1825aTiliqua rugosa (Gray, 1825a)

(Fig. 8J)REFERRED MATERIAL. QMF44603-605, osteoderms.

DESCRIPTION. Osteoderms. Up to 10mm indiameter; thick, coarsely pitted; rugose surface.

REMARKS. The osteoderms of Tilqua rugosadiffer from all other Tiliqua as they are generallythicker and more coarsely pitted, functioning toform an armoured shield (Hutchinson, 1993).[Smith, 1976]

Cyclodomorphus Fitzinger, 1843Cyclodomorphus sp.

(Fig. 8K)REFERRED MATERIAL. QMF44639, dentary.

DESCRIPTION. Dentary. Near complete withlarge hemispherical teeth and closed Meckel’sgroove; ventral symphysal crest extends to thirdtooth; ten teeth present in dentary with tenth toothmarkedly larger than all anterior teeth; teethvariable in size, with acutely conical crowns;

specimen is adult as dental sulcus well defined,and dentary indicates cycles of toothreplacement.

REMARKS. Cyclodomorphus spp. are similar insize to Tiliqua spp., but are distinguished by amarkedly larger tenth tooth in the dentary(Hutchinson, 1993). The fragmentary nature ofthe fossil remains precludes a full comparison toother members of the genus. [Shea ,1990]

Family VARANIDAE Hardwicke & Gray,1827.

Varanus Merrem 1820Varanus sp.

(Fig. 8L)

REFERRED MATERIAL. QMF48166, vertebra.

DESCRIPTION. Vertebra broken dorsally;condyle overhanging, oblique articulation; cotyleoblique; centrum broad; neural canal round.

REMARKS. The fragmentary nature of thevertebra, particularly the lack of neural spine,precludes a full comparison to other Varanus spp.[Smith,1976].

Megalania Owen, 1860Megalania prisca (Owen, 1860)

(Fig. 8M)

REFERRED MATERIAL. QMF44615-17, osteoderms.

DESCRIPTION. Small , worm shapedosteoderms to 8mm in length, 3mm in diameter;growth lines evident.

REMARKS. Megalania prisca osteoderms growin the snout and nape regions of the lizard(Erickson et al., 2003). Growth lines present onthe osteoderms may reflect the age of theindividual (Erickson et al., 2003). [Hecht, 1975]

Family ELAPIDAE Boie, 1827gen. et sp. indet.

(Fig. 8N)

REFERRED MATERIAL. QMF44606-08,vertebrae.

DESCRIPTION. Vertebrae with long, acuteaccessory processes; hypapophysis arises nearlip of cotyle, extends posteriorly for half thelength of centrum, then deepens to taper into asharp point; parapophysial processes roundedanter ior ly; neural spine low, lateral lycompressed, does not extend posteriorly; fourpairs of foramina present.


106

REMARKS. Elapid vertebrae considered hereare comparable in size to extant forms currentlyfound on the Darling Downs today, suchPseudechis australis and P. porphyriacus.[Smith,1976]. However, the fragmentary natureof the fossil material precludes a full comparisonto other members of the family.

Class MAMMALIA Linneus, 1758Order MARSUPIALIA Cuvier, 1817

Family DASYURIDAE Goldfuss, 1820; sensuWaterhouse, 1838

Sminthopsis Thomas, 1887Sminthopsis sp.

(Fig. 9A)REFERRED MATERIAL. QMF44637, dentary.

DESCRIPTION. Dentary. Small, gracile,deepest below M1; mental foramenposteroventral to root of M1. P3 ovoid in occlusaloutline; anterior cuspid reduced, lingual tomidline, forming anterior margin; central cuspidmassive, positioned one third from anteriormargin; blade-like crest runs posteriorly to asmall posterior cuspid. M1 anterior one-thirdtriangular, remainder sub-rectangular in occlusaloutline; talonid wider than trigonid; protoconidtallest cusp on crown, followed by metaconid,hypoconid, paraconid and entoconid; paraconidforms anterior margin slightly lingual to midline;protoconid posterobuccal to paraconid;metaconid transverse and slightly posterior toprotoconid; hypoconid posterobuccal toprotoconid; entoconid most posterior cuspforming posterolingual corner of crown; anteriorand posterior cingula small but distinct;

metacristids and hypocristids transverse to longaxis.

REMARKS. Identification to specific level is notpossible due to insufficient preservation ofdiagnostic features. [Archer,1981]

Dasyurus Geoffroy, 1796Dasyurus sp.

(Fig. 9B)

REFERRED MATERIAL. QMF44597, M4.

DESCRIPTION. M4. Ovoid in occlusal outline;paracone tallest cusp on crown followed indescending order by stylar cusp B, metacone andprotocone; paracone most anterior cusp,positioned in midline of crown; Stylar cusp Bposterobuccal to paracone; metacone postero-lingual to paracone; anterior cingulum absent.

REMARKS. M4 described above is much largerthan the corresponding tooth in all species ofDasyurus excepting D. maculatus. It is wellwithin the size range of extant D. maculatus,although differs in that: 1) it is not anteriorlyconcave in occlusal outline, 2) the metacone ispositioned more lingually, and 3) the anteriorcingulum is absent. [Ride,1964].

Sarcophilus Cuvier, 1837Sarcophilus sp.

(Fig. 9C)

REFERRED MATERIAL. QMF44640, C1.

DESCRIPTION. C1. Enamel constricted toanterior one-quarter of tooth; curved slightly inocclusal view and is deepest one-third from


FIG. 9. A. Sminthopsis sp., left dentary; B. Dasyurus sp., M4; C. Sarcophilus sp., C1; D. Thylacinus cynocephalus,I1; E. Perameles bougainville, M1; F. P. nasuta, M3.

107

enamelised tip of tooth; root laterally compressedtapering to a blunt point.

REMARKS. QMF44640 compares well to thecorresponding tooth of recent Sarcophilus harissialthough is slightly larger and may represent thePleistocene S. laniarius. [Ride, 1964]

Family THYLACINIDAE Bonaparte, 1838

Thylacinus Temminck 1824Thylacinus cynocephalus (Harris, 1808)

(Fig. 9D)

REFERRED MATERIAL. QMF44643, I1.

DESCRIPTION. I1. Markedly curved in lateraland occlusal view; enamel constricted to theanterior one-quarter of tooth and tapers to anacute point; deepest and broadest half way alonglength of entire tooth; root laterally compressed,deep, with posterior half tapering to an acutepoint.

REMARKS. QMF44643 is morphologicallysimilar to the corresponding tooth of recentThylacinus cynocephalus. [Ride,1964]

Family DIPROTODONTIDAE Gill, 1872

Diprotodon Owen, 1838Diprotodon sp.

(Fig. 10A)

REFERRED MATERIAL. QMF44649, P3.

DESCRIPTION. P3. Sub-rectangular in occlusaloutline; bilophid with lophs connected by a highlingual crest; anterior lophid markedly largerthan posterior lophid; enamel thick with aworm-eaten puncate appearance.

REMARKS. Diprotodon sp. is distinguishedfrom other diprotodontids by possessing abilophodont lower premolar, with thick,punctated enamel. [Archer,1977]

Family THYLACOLEONIDAE Gill, 1872

Thylacoleo Owen 1858Thylacoleo carnifex Owen, 1858

(Fig. 10B)

REFERRED MATERIAL. QMF44642, I1.


FIG. 10. A. Diprotodon sp., P3; B. Thylacoleo carnifex, I1; C. Aepyprymnus sp., M3; D. Troposodon minor, rightdentary; E. Procoptodon pusio, left dentary; F. Macropus agilis siva, right dentary; G. M. titan, right dentary; H.Protemnodon anak, left dentary; I. P. brehus, right maxilla.

108

DESCRIPTION. I1. markedly curved in occlusalview with enamel confined to anterior and lateralsurface in a U shape; occlusal wear surfaceconcave; root deep and laterally compressed.

REMARKS. Thylacoleo carni fex isdistinguished from other members of the genusby its significantly larger size. [Wells et al., 1982]

Family POTOROIDAE Gray, 1821; sensuArcher & Bartholomai, 1978

Aepyprymnus Garrod, 1875Aepyprymnus sp.

(Fig. 10C)

REFERRED MATERIAL. QMF44652, M3.

DESCRIPTION. M3. metalophid low and verythin, but distinct; postmetacrista connects toposterior cingulum to form a very large and fairlydeep pocket-like structure on posterior margin oftooth; premetacrisa well defined.

REMARKS. Fragmentary material precludes afull comparison to Aepyprymnus rufescens, theonly the only known member of the genus. [Tate,1948]

Family MACROPODIDAE Gray, 1821Subfamily STHENURINAE Glauert, 1926

Procoptodon Owen 1874Procoptodon pusio (Owen, 1874)

(Fig. 10E)

REFERRED MATERIAL. QMF44648, dentary.

REMARKS. Dentary. Short, deep and robust;buccal groove on ramus well defined.Lower molars. Sub-rectangular in occlusaloutline, with slight constriction in midvalley;base of molars swollen and lophids high, convexanteriorly; enamel crenulated, though smooth onlingual and buccal lateral surfaces; anteriorcingulid is high, angled slightly lingually.

REMARKS. Propcoptodon pusio isdistinguished from other members of the genusby a combination of characters including: 1) itsslightly smaller size, 2) lacking a distinctposthypocristid, and 3) less extensive transverseanterior portion of paracristid (Prideaux, 2004).The horizon from which the P. pusio material wascollected is unknown. Procoptodon is restrictedto Pleistocene deposits, though may have had itsorigins in the late Tertiary (Bartholomai, 1970;Prideaux, 2004). [Prideaux, 2004]

Subfamily MACROPODINAE Gray, 1821

Troposodon Bartholomai 1967Troposodon minor (Owen, 1877b)

(Fig. 10D)

REFERRED MATERIAL. QMF44646-47, dentaries.

DESCRIPTION. Dentary. Shallow and gracile;symphysis elongate with ventral surfacemarkedly lower than ventral surface of ramus.Lower molars. Subrectangular in occlusaloutline, with slight kink in midvalley; lophs low,angled slightly lingually, and slightly concaveanteriorly; preparacristid links to anteriorcingul id; premetacr is t id descendsanterolingually from metaconid to fuse withpreparacristid.

REMARKS. Troposodon minor is placed withinMacropodinae rather than Sthenurinae followingPrideaux (2004). T. minor is easily distinguishedfrom other members of the genus by beingintermediate in size between the larger T. kentiand smaller T. bowensis. [Flannery and Archer,1983]

Macropus Shaw 1790Macropus agilis siva (De Vis, 1895)

(Fig. 10F)

REFERRED MATERIAL. QMF44638, I1; QMF44655,dentary; QMF44656-7, maxillary fragments.

DESCRIPTION. Dentary. Gracile, with grooveon ventral surface of ramus extending fromposterior of symphysis to below posterior root ofM2; symphysis elongated and diastema long. I1.Elongated and deeply rooted; slightly curved inboth lateral and occlusal views. P3. Elongated,blade-like; small ridges descend lingually andbuccally from apex of longitudinal ridge.Lower molars. Increase in size from M1-3;sub-rectangular in occlusal outline, with slightconstriction in midvalley; hypolophid wider thanprotolophid; lophids high; cristid obliqua high;posterior cingulid absent. DP2 elongated, broadposteriorly; small ridges descend main crest;posterolingual fossette shallow. DP3 molariform;subrectangular in occlusal outline with slightconstriction in midvalley; lophs low; metalophwider than protoloph; posterior fossettemoderately developed. M1 sub-rectangular inocclusal outline, with slight constriction inmidvalley; high lophs; metaloph broader thanprotoloph; midlink moderately high; posteriorfossette well developed.


109

REMARKS. Macropus agi l is s iva isdistinguished from other members of the genusby possessing a combination of featuresincluding: 1) elongate diastema, 2) P3 as long asM1, 3) lower molars high crowned, with highlinks, and lacking posterior cingula, 4) elongateupper premolars, and 5) upper molars elongatedwith high crowns, slight forelink and moderatemidlink. [Bartholomai,1975]

Macropus titan Owen, 1838(Fig. 10G)

REFERRED MATERIAL. QMF44645, dentary.

DESCRIPTION. Dentary. moderately deep, thebase of symphysis slightly lower than the base ofhorizontal ramus.Lower molars. Sub-rectangular in occlusaloutline, slightly constricted across talonid basin;lophids high and curved slightly anteriorly;forelink high, curving anteriorly to meet a highanterior cingulid; posterior fossette present onposterior loph.

REMARKS. Macropus titan is distinguishedfrom other members of the genus by acombination of features including: 1) its largesize, 2) elongate diastema, 3) high crowned,elongated lower molars with slightly curvedlophids, high links and high anterior cingulum(Bartholomai, 1975). An additional dentaryfragment, QMF44644, is referred to M. sp. cf. M.titan. The molars are within the size range of M.titan, however it differs in that: 1) the dentary ismarkedly more robust and deep, 2) forelink isslightly lower, 3) anterior cingulid broader, and4) cristid obliqua is higher. [Bartholomai,1975]

Protemnodon Owen 1874Protemnodon anak (Owen, 1874)

(Fig. 10H)

REFERRED MATERIAL. QMF44650, skull;QMF44658, dentary.

DESCRIPTION. Dentary. Moderately shallow,with elongated symphysis ascending anteriorly atlow angle; mental foramen oval shaped, close todiastemal crest. P3. Elongated, blade-like;exceeds length of M1.Lower molars. Sub-rectangular in occlusal viewwith slight constriction in midvalley; lophidshigh, concave anteriorly with high forelink;posterior cingulid small P3. Elongate; crownconcave buccally; high longitudinal crest,slightly concave buccally; transected by fourvertical blades.

Upper molars. Sub-rectangular in occlusaloutline, slightly constricted across mid valleys;midlink strong; forelink absent; anteriorcingulum slightly swollen.

REMARKS. Protemndon anak is distinguishedfrom other Pleistocene members of the genus by acombination of characters including: 1) smallsize, 2) P3 elongate, concave bucally, with highlongitudinal crest, and longer than M4, 3) M3 andM4 lacking cuspules in the lingual portion of themidvalley. [Bartholomai,1973]

Protemnodon brehus (Owen, 1874)(Fig. 10I)

REFERRED MATERIAL. QMF44627, maxilla.

DESCRIPTION. Upper molars. Sub-rectangularin occlusal outline, slightly constricted acrossmidvalley; anterior cingula broad; forelinkabsent; strong ridge curves from paracone intocrista obliqua.

REMARKS. Protemnodon brehus isdistinguished from other members of the genusby: 1) its large size, and 2) lacking a lingualcuspule in the midval ley of M3 - 4 .[Bartholomai,1973]

Order RODENTIA Bowdich, 1821.Family MURIDAE Illiger, 1811

Pseudomys Gray 1832Pseudomys sp. 1 & 2

(Fig. 11A)REFERRED MATERIAL. Sp. 1: QMF44609-10,maxillae; Sp.2: QMF48168, maxilla.

DESCRIPTION. Maxilla. Anterior portion ofzygomatic arch not broadened; molar alveolipattern 3(M1) 3(M2) 3(M3). M1. Relativelyelongate; T7 absent; three rooted, with onelingual root.

REMARKS. Pseudomys sp. 1 and 2 could not beidentified to specific level considering the natureof the fragmentary remains. Pseudomys sp. 1 fitswithin the size class of extant P. australis.Pseudomys sp. 2 is smaller, approximating thesize of extant P. delicatulus . [Jones &Baynes,1989]

Rattus sp. (Fischer, 1803)(Fig. 11B)

REFERRED MATERIAL. QMF44611-12, isolatedmolars; QMF44613-14, maxillae.

DESCRIPTION. M1. Cusps rounded in occlusaloutline; two lingual cusps; five rooted, with two


110

lingual alveoli. M2. Four rooted, arranged in asquare pattern.

REMARKS. Rattus spp. are distinguished fromother murid genera by possessing an M2 that hasfour roots, arranged in a square pattern (Knox,1976). [Jones & Baynes,1989]

MATERIAL ASSIGNED TO OTHER TAXA

Teleostei fam. gen. et sp. indet. (Fig. 8A); QMF44634-36,vertebrae.

Limnodynastes tasmaniensis (Gnther, 1858) (Fig. 8B);.QMF43978-43985, ilia.

L. sp. cf. L. dumerili (Peters, 1863) (Fig. 8C);QMF43995-43997, ilia.

?Limnodynastes (Fitzinger, 1843)(Fig. 8D); QMF44000,ilium.

Neobatrachus sudelli (Lamb, 1911) (Fig. 8E);QMF44001-44002, ilia,

Kyarranus sp. (Fig. 8F); QMF44003, ilium.

Chelidae gen. et sp. indet. (Fig. 8G); QMF44626;QMF44641, carapace fragments.

Perameles bougainville (Quoy & Gaimard, 1824) (Fig.9E); QMF44549, RM1,.

Perameles nasuta (Geoffroy, 1804) (Fig. 9F);QMF44566, LM3.

ECOLOGICAL REMARKS

Elements of the fauna are here listed withminor pertinent ecological comments asappropriate.

MOLLUSCS. The invertebrate fauna is rich anddiverse. Four families of land snails arerepresented, comprising seven species, as well astwo families of freshwater snails, containing twospecies (J. Stanisic, pers. comm.). Freshwaterbivalves are also common throughout the mainfossiliferous units.Velesunio ambiguus (Philippi, 1847): This mostcommon species of the Australian Unioniodea,occurs in coastal and interior rivers throughoutSouth Australia, Victoria, New South Wales andQueensland (Lamprell & Healy, 1998). Velesunioambiguus is a typical floodplain speciescommonly found in billabongs and creeks; itrarely occurs in large rivers, except in the vicinityof impoundments (Sheldon & Walker, 1989).The exclusion of V. ambiguus from larger riversprobably reflects its weak anchorage (Sheldon &Walker, 1989).Extant populations of Velesunio ambiguus arecommon throughout the creeks and tributaries ofthe Darling Downs. Additionally, V. ambiguushas been recorded from the Pleistocene DarlingDowns (Gill, 1978; Sobbe, 1990).Corbicula (Corbiculina) australis (Deshayes,1830): C. (C.) australis occurs in coastal andinland rivers and streams. It is a hermaphroditicspecies that has a benthic crawling larva thatmakes it possible for C. (C.) australis to spreadrapidly (Britton & Morton, 1982).Extant C. (C.) australis are common throughoutwater courses of the Darl ing Downs.Additionally, C. (C.) australis has been reportedfrom the Pleistocene Darling Downs (Gill, 1978;Sobbe, 1990).Thiara (Plotiopsis) balonnensis (Conrad,1850): T. (P.) balonnensis was the most commonidentifiable species recovered from the deposit. Itwas collected in-situ from shell beds up to 10cmthick. It is the most widespread of the Australianthiraids, common throughout the Murray-Darling River system.Extant populations commonly occur in ponds,dams and rivers (Smith & Kershaw, 1979).Extant populations of Thiara (Plotiopsis)balonnensis are present on the Darling Downs.Thiara (P.) sp. has been reported from the fossilrecord of the Pleistocene Darling Downs (Gill,1978; Sobbe, 1990).Gyraulus gilberti (Dunker, 1848): Planorbidsare a common Australian family of freshwatersnails. The Planorbidae are confined to waterswith low salinity and are generally associatedwith macrophytes or algae. Gyraulus has been


FIG. 11. A. Pseudomys sp. 1, left maxilla; Rattus sp.,left maxilla.

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reported in the Tertiary fossil record of northernAustralia (McMichael, 1968).Saladelos sp.: Saladelos sp. commonly occur inclosed to open forest to vine thicketed habitats (J.Stanisic pers. comm.).Strangesta sp.: Strangesta sp. commonly occurunder dry, dense ground cover in dry forest towoodland scrub, and vine thickets (Smith &Kershaw, 1979; J. Stanisic pers. comm.).Coenocharopa sp.: Coenocharopa sp. aregenerally found in warmer temperate forestthickets to cool, dry, sub-tropical notophyll vineforests from the central to north eastern coast ofthe Australian continent (Stanisic, 1990).Gyrocochlea sp. 1 and 2: Members ofGyrocochlea typically inhabit dry to humidsub-tropical vine forests and prefer to live underlogs (Stanisic, 1990). Like most charopids,Gyrocochlea sp. are common throughout centraleastern Australia (Stanisic, 1990).Austrosuccinea sp.: Austrosuccinea are landsnails that are found in a variety of habitatsranging from marches and swampyenvironments, to sand dunes and seasonally drystream basins (Solem, 1993).Xanthomelon pachystylum (Pfeiffer, 1845):Camaenids are among the most diverse ofAustralian land snails. The Australian camaenidfossil record is scant with only a few knownrecords (Ludbrook, 1978, 1984; McMichael,1968; Kear et al., 2003). X. pachystylum is aherbivorous species associated with dense vinethickets (J. Stanisic, pers. comm.).

AMPHIBIANSLimnodynastes tasmaniensis (Gnther, 1858):Extant L. tasmaniensis populations are commonover much of eastern Australia and have beenrecorded in a range of habitats ranging from wetcoastal environments to dry, arid regions(Cogger, 2000).Extant populations of L. tasmaniensis have beenrecorded from the Darling Downs (Ingram &Longmore, 1991).L. sp. cf. L. dumerili (Peters, 1863): Extantpopulations have been recorded in most habitats,with the exception of alpine areas, rainforest, andextremely arid zones (Cogger, 2000).Extant populations of L. dumerili have beenrecorded from the Darling Downs (Ingram &Longmore, 1991).Neobatrachus sudelli (Lamb, 1911)

Extant populations of Neobatrachus sudellioccur throughout southeastern Australia,commonly occurring in open woodlands withgrassy understories (Cogger, 2000).

Kyarranus sp.Extant Kyarranus populations occur in areas of

dense ground cover and thickets in isolatedmontane forest patches on the Great DividingRange in southeastern Queensland andnortheastern New South Wales (Tyler, 1991).

REPTILES

Tympanocryptis “lineata” (Peters, 1863):Extant T. lineata populations occur in a variety ofsemi-arid to arid environments in centralAustralia. T. lineata commonly occur in earthcracks, grass or ground litter on desert sandhills,to black soil plains (Cogger, 2000).

Extant T. lineata populations have been recordedfrom the Darling Downs (Covacevich & Couper,1991). Additionally, agamids have previouslybeen recognised in the Darling Downs fossilrecord (Bennett, 1876; Lydekker,1888; Molnar &Kurz,1997).

“Sphenomorphus Group” sp. 1 and 2: Theecology of extant members of theSphenomorphus group is varied and includes taxathat burrow in soil, burrow under leaf litter, havesemi-amphibious lifestyles and others that arefound in rocky arid environments (Cogger,2000).

Til iqua rugosa (Gray, 1825a): Extantpopulations of T. rugosa are found in a range ofhabitats including coastal heaths, dry sclerophyllforest, woodlands, mallee, and arid Acacia andeucalypt scrublands. T. rugosa shelters underfallen timber and leaf litter spinifex wheninactive (Cogger, 2000).

Cyclodomorphus sp.: Cyclodomorphus spp. areground dwelling skinks, although commonlyclimbs on low growing vegetation. ExtantCyclodomorpus populations have been recordedfrom wet to dry sclerophyll forest, commonlyfound under leaf litter or areas with low groundcover (Cogger, 2000).

Varanus sp.: Extant Varanus sp. populationshave been recorded in a wide range of habitatsfrom deserts to rainforest, and may havesemi-aquatic, terrestrial, or arboreal locomotivestrategies.

Extant Varanus populations have beenrecorded from the Darling Downs (Covacevich &Cooper, 1991). Additionally, Varanus sp. has

DARLING DOWNS PALAEOECOLOGY

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been recorded from the Pleistocene DarlingDowns (Wilkinson, 1995).

Megalania prisca (Owen, 1860): Molnar (1990)suggested that M. prisca was unlikely to havebeen arboreal, though it may have had asemi-aquatic life style.

Megalania prisca has been recorded from severalfossil localities on the Darling Downs (Molnar &Kurz, 1997).

Other elements: Indeterminate chelid and elapidremains have been found in the deposit.

MARSUPIALS

Sminthopsis sp.: Extant Sminthopsis spp.populations occur in open to closed habitats(Strahan, 1995).

Extant populations of S. murina have beenrecorded on the Darling Downs (Van Dyck &Longmore, 1991).

Dasyurus sp.: Dasyurus maculatus is the largestextant native mammalian carnivore on themainland of Australia. Dasyurus spp. are partlyarboreal and occur on the eastern margin of thecontinent and Tasmania in a wide range ofwooded habitats including rainforests, openforests, woodlands, and riparian forest. Den sitescommonly include caves, rock crevices andhollow logs.

Sarcophilus sp.: Once common over the centraland eastern portions of the Australian continent,Sarcophilus is now restricted to Tasmania whereit is abundant in dry sclerophyll forest andwoodlands that are interspersed with grasslands(Jones, 1995).

Thylacinus cynocephalus (Harris, 1808): Priorto European arrival in Australia, extant T.cynocephalus was restricted to Tasmania beforeover hunting led to its subsequent extinction. T.cynocephalus was once common in open forestand woodland (Dixon, 1989).

Perameles bougainville (Quoy & Gaimard,1824): Extant populations of P. bougainville arerestricted to Bernier and Dorre Islands, SharkBay, Western Australia, although once occurredover much of semi-arid Australia (Friend &Burbidge, 1995). Extinction on the mainland hasbeen attributed to the effects of habitatdisturbance and introduction of non-nativepredators by Europeans. P. bougainville was oncecommon on the mainland in a range of habitatsincluding dense scrub thickets, open saltbushplains and stoney ridges bordering scrubland(Friend & Burbidge, 1995).

Perameles nasuta (Geoffroy, 1804): ExtantPerameles nasuta populations occur in a widerange of habitats including rainforests, wet to drywoodlands, and areas with very little groundcover (Stoddart, 1995). It is a common andwidely distributed species with a wide range ofhabitat tolerances, and its presence in the fossilrecord is of li t t le palaeoenvironmentalsignificance.Extant Perameles nasuta populations arecommon on the Darling Downs.Diprotodon sp.: Diprotodon spp. are generallyregarded browsers of shrubs and forbs andprobably occupied an open woodland to savannahabitat (Murray, 1984).Thylacoleo carnifex (Owen, 1858) : T. carnifexmay have occupied an open forest habitat(Murray, 1984). T. carnifex filled the ‘large cat’niche of the Australian Pleistocene, and mayhave had the ability to kill Diprotodon-sizedanimals (Wroe, et al., 1999). The lower incisorfunctioned as a stabbing or piercing tooth thatoccludes with the upper incisors where it acts asan anvil against which food is restrained (Wells etal. 1982).T. carnifex has been recorded from several fossillocalities on the Darling Downs (Molnar & Kurz,1997).Aepyprymnus sp.: Extant A. rufescenspopulations occur in a variety of habitats rangingfrom wet sclerophyll to dry open woodlands, butonly occupy areas with sparse grassyunderstories commonly adjacent to areas ofdense undergrowth (Dennis & Johnston, 1995).Procoptodon pusio (Owen, 1874): Procoptodonspp. were adapted for a diet of highly fibrousvegetation (Prideaux, 2004).P. pusio has been recorded from several fossillocalities on the Darling Downs (Molnar & Kurz,1997; Prideaux, 2004).Troposodon minor (Owen, 1877b): Troposodonminor is generally regarded as a semi-browser(Bartholomai, 1967). Flannery & Archer (1983)suggested that at least two species of Troposodonoccurred sympatrically at most Plio-Pleistocenelocalities. However, T. minor remains the onlymember of the genus recorded at QML1396.Troposodon minor is relatively common inPleistocene Darling Downs deposits (Molnar &Kurz, 1997).Macropus agilis siva (De Vis, 1895): ExtantMacropus agilis populations favour savannahwoodland or open forest habitats (Bell, 1973).


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M. a. siva was common and widespread on thePleistocene Darling Downs (Molnar & Kurz,1997).Macropus titan (Owen, 1838): The highcrowned molars M. titan are typical of grazingspecies (Bartholomai, 1975).M. titan was one of the most common andwidespread megafauna species on the DarlingDowns, being recorded from 21 fossil deposits(Molnar & Kurz, 1997).Protemnodon anak (Owen, 1874),Protemnodon brehus (Owen, 1874):Protemnodon spp. are regarded as grazers(Bartholomai, 1973).P. anak and P. brehus have been recorded fromover 30 fossil localities on the Darling Downs(Molnar & Kurz, 1997).

RODENTSPseudomys sp. 1 & 2: Extant Pseudomys spp.populations occur in a wide variety of habitatsfrom sparsely vegetated deserts to closedsclerophyll forests (Strahan, 1995). Until thetaxonomy of the Pleistocene Darling DownsPseudomys spp. is better known, theirpalaeoenvironmental significance will remainunclear.Pseudomys spp. have been recorded from thePleistocene Darling Downs (Archer & Hand,1984).

Rattus sp.: In terms of abundance and diversity,Rattus is the most diverse extant murid genus inQueensland. Extant Rattus populations are found ina number of habitats including rainforests,woodlands, and savanna grasslands.

Extant Rattus spp. populations (native andintroduced) have been recorded from the DarlingDowns (Covacevich & Easton, 1974). Additionally,Rattus sp. has been reported from the PleistoceneDarling Downs (Archer & Hand, 1984).

DATING.

The AMS14C dating results of freshwaterbivalves and charcoal indicate that deposition ofHorizon B occurred 44300± 2200 to >49900 andHorizon D at 45150±2400 (Table 9). However,those results should be considered as minimumages only considering the fact that the QML1396assemblage appears to be close the limits of theAMS14C dating technique. Owing to theimportance associated with dating latePleistocene megafauna extinction and climate

change, it is desirable to further test the datingresults presented here.

DISCUSSION

SEDIMENTOLOGY. The deposit representsboth high velocity lateral channel deposition andlow velocity vertical accretion. The lowerfossiliferous unit, Horizon B, represents the mostsignificant input of sandy deposits in thesedimentary environment. Horizon B is laterallycontinuous for more than 70 metres. However,the horizon is largely unexposed and positionedbelow the modern water table, therefore theprecise lateral extent of Horizon B is unknown.Horizon B is characterised by: 1) abundantfreshwater mollusc fossils, including large-sizedbivalves; 2) vertebrate fossils; 3) fluviallytransported sediments (including rounded basalt,calcrete and sandstone pebbles and cobbles); and4) upwardly fining grain size. The geometry ofHorizon B and the interpreted sedimentaryprocesses suggest that deposition took place inthe main channel. Horizon B accumulated underhigher velocity deposition than Horizon Dconsidering the significantly larger grain sizesand preponderance of larger-sized bivalves (Fig.2, Table 1).

The fine brown-grey clay unit, Horizon C,suggests a period of low velocity deposition.Mollusc shells are rare, however, freshwatergastropods (Thiara (Plotiopsis) balonnensis) areslightly more common than freshwater bivalves.The presence of freshwater molluscs in thehorizon are consistent with the proximity to thechannel.

Horizon D is laterally continuous forapproximately 30 metres. Horizon D ischaracterised by: 1) discontinuous lenticularsandy and shelly beds; 2) mud cracks in-filledwith fine clays; 3) vertebrate fossils; and 4)fluvially transported sediments (includingrounded basalt, calcrete and sandstone pebbles).The facies association of lenticular shelly beds


ANSTO code sample horizon conventional 14C age �

2� error

OZG855 charcoal D 45150 � 2400

OZG547 bivalve B >49900

OZG548 bivalve B 44300 � 2200

TABLE 9. AMS 14C dating results of charcoal andVelesunio ambiguus samples from QML1396. Agesquoted are radiocarbon ages, not calendar ages. Agesrounded according to Stuiver & Polach (1977)

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overlies the low velocity brown-grey clay unit (incontinuity with the channel deposit). Freshwatergastropods in Horizon D show polymodal currentdirections indicating that they were not depositedas traction load in flowing water. The datasuggest that deposition occurred as overbankdeposits on the floodplain adjacent to the channelbelt. A succession of several small overbankdepositional events created superposed shellylenses up to 100mm thick. The depositionalset t ing of Horizon D is interpreted asrepresenting a series of small crevasse splays andsubsequent drying pools in the overbank thatresulted from minor flood events. It ishypothesised that as the pools evaporated,stranded gastropods moved into the deeper partsof the pools (hence showing polymodalorientations) eventually dying when the poolsevaporated.

Overlying fine-grained deposits of the upperunits represent vertical accretion on thefloodplain (Fig. 2, Table 1). The occurrence ofiron nodule formation in the upper units of theprofile reflect alternating periods of oxidationand reducing conditions due to watertablefluctuations. Additionally, in-situ, white tobrownish-grey mottled calcrete formation in theupper units is related to similar watertablefluctuations. Mottled calcretes are chemicallyprecipitated in the freshwater phreatic zone of thewatertable, and are primarily related to the lateralmovement and percolation of alkaline waters inthe soil profile (Arakel & McConchie, 1982). Theclose association of the formation of in-situmottled calcretes and ferruginous oxides areindicative of a response to an increasingly aridenvironment, subsequent to deposition of themajor fossiliferous horizons.

TAPHONOMIC HISTORY OF BONES.

Numerous unidentifiable bone fragmentsrecovered from the deposit exhibited a range ofabrasion and weathering characteristics.However, the following taphonomic conclusionsare largely based on identifiable vertebrateremains horizons B and D. Better preservedspecimens may yield more accuratepalaeobiological and palaeoecologicalinformation than unidentifiable fragments.However, it is recognised that some componentsof the assemblage may have had differenttaphonomic pathways leading to their finaldeposition.

It is unlikely that acidic ground waters haveplayed a role in the diagenesis of fossil material

from either horizon, considering the high degreeand diagentically unaltered preservation ofcalcareous material (i.e. mollusc shell andcalcrete) that has been identified in the deposit.Additionally, root etching of vertebrate fossilmaterial was not observed. Few of theidentifiable specimens indicate any significantpre-burial weathering (sensu Behrensmeyer,1978).

There were several biases in the preservation ofdifferent faunal groups and skeletal elementsobserved in the deposit. For squamates, there wasa noticeable lack of post-cranial materialpreserved in the deposit in comparison tomammals. Similar biases between terrestrialnon-mammals and mammals have beenidentified within fossil deposits of the KoobiFora Formation of Kenya (Behrensmeyer, 1975).Additionally, within the Agamidae andScincidae, differences were observed in thepreservability of cranial and dental elements. Thedifferences may be related to minor differences inbone density or structure. However, few previousstudies have addressed the causes of suchpreservational biases, focusing predominantly onthe accumulation of fossil mammals. In theabsence of comparative data on squamatetransportability and preservability in fluvialsystems, it is difficult to explain such biases in thefossil record.

Large-sized mammals are better preserved inHorizon B than Horizon D, but small-sized taxaare generally absent from Horizon B. Bones andshells act as sedimentary particles in fluvialsystems and may have settling velocities that arerelated to equivalent-sized spherical quartzgrains (Behrensmeyer, 1975). Therefore, if thesize of bone and shells are relative to the size ofthe surrounding grains, then coarse-grained unitssuch as Horizon B would be expected to containlarger-sized skeletal elements or species thanfiner-grained units such as Horizon D. Thathypothesis may equally explain: 1) whylarge-sized bivalves are more common inHorizon B than Horizon D; 2) why the Horizon Bassemblage is dominated by large-sizedvertebrates, and Horizon D by small-sizedvertebrates; and 3) the differences between therelative abundance of skeletal elements of largeand small mammals within Horizon D.

Assemblages of both horizons are generallycharacterised by: 1) low levels of post-crania; 2)high degrees of bone breakage; 3) low degrees ofabrasion; and 4) low degrees of weathering. A


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comparison of the abundance of skeletalelements to experimental data of skeletal elementtransportability in fluvial systems indicates thatboth units contain elements that are among thelast to be transported in flowing water. Thatsuggests that horizons B and D represent bone lagdeposits. The high degree of breakage of skeletalelements suggests that the vertebrate remainswere subjected to considerable forces.Additionally, the loss of limb bone ends mayreflect a density mediated destruction oflower-density bone (distal and proximal ends)and that the higher-density bone shafts were notdestroyed (Rapson, 1990). The low degree ofbone abrasion and low degree of pre-burialweathering indicate that the vertebrates diedwithin close proximity to the final point ofdeposition and were probably buried rapidly afterdeath. Additionally, no elements were recoveredthat show the effects of digestion, polishing orgnawing that may be attributable to predatoraccumulation (sensu Andrews, 1990; Sobbe,1990). Collectively, the data indicate that thevertebrate material was accumulated andfluvially transported into the deposit from thesurrounding proximal floodplain.

PALAEOENVIRONMENTALINTERPRETATION

Megafauna species are less abundant and lesswell preserved in Horizon D (low-energyoverbank deposi t ion) than Horizon B(high-energy channel deposition), and allvertebrate taxa smaller than Sarcophilus sp. (~8kg) are absent from Horizon B (Figure 6). Threehypotheses could explain the faunal differences:1) Megafauna went locally extinct progressivelybetween the time of deposition of Horizons B andD (the age of the two QML1396 assemblagesmay bracket the terminal extinction event of theAustralian megafauna [~46ka; Roberts et al.,2001a]); 2) Sampling by the creek system wasbiased towards the collection of small-sizedspecies in Horizon D; or 3) Larger-sized bonesmay not have been able to be transported intooverbank deposits from flood events (large bonesin the overbank deposits may be derived directlyfrom the proximal floodplain rather than fromfluvial transport). Additionally, a third of thelarge-sized taxa that are present in Horizon B, butabsent from Horizon D, are carnivorous species(Sarcophilus sp., Thylacinus cynocephalus &Thylacoleo carnifex; Table 2). Hence, the rarityof carnivorous taxa in the Pleistocene DarlingDowns might be assumed regardless. However,

considering the taphonomic sampling biases ofthe Pleistocene channel, it is difficult toaccurately compare habitat and speciesdifferences between the Horizon D and Bassemblages, and hence, directly demonstrate theextinction of megafauna temporally based ondata from QML1396.

Large-sized taxa previously used to makeinterpretations about Darling Downs Pleistocenepalaeoenvironments are present in the Horizon Bassemblage, thus in agreement with previousbroad interpretations of a woodland and opengrassland Pleistocene habitat (Table 10). All ofthe mammals recorded from Horizon B are eitherlocally or totally extinct.

The Horizon D assemblage consists of largeand small-sized taxa that are extant, locally ortotally extinct. The small-sized faunas haverevealed a series of increasingly complexterrestrial habitats, some that have not previouslybeen documented in the Pleistocene DarlingDowns. It appears that at the time of deposition ofHorizon D, a suite of habitats existed thatconsisted of grasslands, open woodlands withgrassy understories, and scrubby vine-thicketedhabitats (Table 11). A scrubby vine thicketedhabitat is indicated predominantly by the diverseland snail fauna. That interpretation isadditionally supported by the presence ofKyarranus, a frog genus whose extant membersare restricted to dense understories and thickets.Vine thickets are common on the Great Dividing


Species freshwater openwoodland

opengrassland

Velesunio ambiguus x

Corbicula(Cobiculina) australis x

Thiara (Plotiopsis)balonnensis x

Sarcophilus sp.* x

Thylacinuscynocephalus** x

Diprotodon sp.** x x

Thylacoleo carnifex** x

Troposodon minor** x

Macropus agilissiva** x

M. titan** x x

Protemnodon anak** x x

P. brehus** x x

TABLE 10. Preferred and inferred habitat types ofextant and fossil taxa recorded from Horizon B. (*Extinct on Darling Downs; ** Totally extinct).

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Range today and support a similar land snailfauna (J. Stanisic, pers. comm.). Additionally,scrubby and closed habitats have previously beensuggested for late Pleistocene deposits of the

Kings Creek catchment (Price, 2004; Price et al.,in press). Woodlands were likely to have beenopen sclerophyll, interspersed with sparse grassyunderstories. That interpretation is highlightedby the presence of taxa such as Austrocuccineasp., Neobatrachus sudelli, Aepyprymnus sp., andMacropus agilis siva. Grasslands were likelydominated by large browsing macropodsincluding Macropus titan and Protemnodon spp.Small agamid lizards such as Tympanocryptislineata probably occupied a similar open habitat,utilizing the earth cracks within black soils.

There are few modern analogues to explain thehigh habitat diversity indicated by the faunarepresented in the Horizon D assemblage.However, considering the relatively constrainedsampling area of the Kings Creek palaeo-catchment, it is unlikely that the diverseQML1396 assemblage resulted from thesampling of wide geographic areas outside theimmediate catchment area (i.e. by long distancefluvial transport). Additionally, taphonomic dataindicates that while the assemblage washydraulically transported, the components wereunlikely to have been transported over longdistances. Collectively, those data suggest that amosaic of grassland, sclerophyllous woodlands,and scrubby vine-thicketed habitats were presentwithin the geographically small PleistoceneKings Creek catchment. Non-analogueassociations of taxa (sensu Lundelius, 1989, as‘disharmonious’ associations) from other sites inthe Kings Creek catchment (e.g. bandicoots fromQML796) support the hypothesis that avegetative mosaic of habitats was present duringthe late Pleistocene (Price, 2004).

Comparison of such Pleistocene habitats tothose of the modern Kings Creek catchment isdifficult considering extensive pastoral activitieswhich have altered natural vegetation in theregion since the early 1840’s. Even where naturalremnant vegetation survives, its current structureand floristics do not necessarily reflect itspre-settlement character. However, a review ofover 5,000 land surveys from periods of theinitial settlement of the Darling Downs indicatesthat the region surrounding the immediate area ofdeposition of QML1396 was dominated bygrasslands, with Eucalyptus orgadophilawoodlands with grassy or shrubby understoriesbeing found closer to the range (Fensham &Fairfax, 1997). Based solely on the numbers ofdifferent species representing the interpretedPleistocene habitats of QML1396, it is evidentthat taxa indicating open grassland habitats are


species

fres

hwat

er

vine

-thi

cket

scru

blan

d

cols

edw

oodl

and

open

woo

dlan

d

open

/gra

ssla

nd

Velesunio ambiguus X

Corbicula (Cobiculina) australis X

Thiara (Plotiopsis) balonnensis X

Gyraulus gilberti* X

Coencharopa sp.* X

Gyrocochlea sp. 1* X

Gyrocochlea sp. 2* X

Austrocuccinea sp.* X X X

Xanthomelon pachystylum* X

Strangesta sp.* X X

Saladelos sp.* X

Teleost X

Limnodynastes tasmaniensis X X X X X

L. sp. cf. L. dumerili X X X X X

?Limnodynastes X X X X X

Neobatrachus sudelli* X X

Kyarranus sp.* X X

Chelid X

Tympanocryptis “lineata”* X

“Sphenomorphus Group” sp. 1 X X X X X

"Sphenomorphus Group” sp. 2 X X X X X

Tiliqua rugosa* X X X

Cyclodomorphus sp.* X X X X

Varanus sp. X X X X X X

Megalania prisca** X X X

Elapid X X X X X X

Sminthopsis sp. X X X X X

Dasyurus sp. X X

Perameles bougainville* X X

Pe. nasuta X X X X X

Aepyprymnus sp X

Macropus agilis siva** X

M. titan** X X

Protemnodon anak** X X

Pr. brehus** X X

Pseudomys sp.* X X X X X

Rattus sp. X X X X X

TABLE 11. Preferred and inferred habitat types ofextant and fossil taxa from Horizon D. (* Extinct onDarling Downs; ** totally extinct).

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the minority, and that species favouringwoodlands and scrubby, vine thicketed habitatsdominate the assemblage (Tables 10 & 11). It ishypothesised that the immediate areasurrounding the Pleistocene watercourse wasdominated by woodlands, scrublands and vinethickets, and that open grasslands were situatedfarther away from the creek. That interpretationsuggests that there must have been significantenvironmental change between the time ofdeposition of QML1396 and present, and thatwould have reflected contraction of woodlandsand vine thickets closer to the range, andexpansion of grasslands in the catchment area.

Deposition of the QML1396 assemblageoccurred around the time of the extinction of theAustralian megafauna, i.e. ~46ka (Roberts et al.,2001a). Hence, it is an extremely importantPleistocene assemblage as it provides detailedinformation about habitats and environmentsduring a critical period for Australian megafauna.The two major hypotheses surrounding theextinction of Australian megafauna are: 1) anaturally driven climate change that coincidedwith the last glacial maximum, and reducedviable habi ta ts for megafauna, and 2)anthropogenic overkill of megafauna ormodificat ion of habitats during ini t ialcolonisation of the continent during the latePleistocene (Martin & Klein, 1984; Diamond,2001, Roberts et al., 2001a; Brook & Bowman,2004; Barnosky et al., 2004; Wroe et al., 2004).While there are numerous examplesdocumenting increasing aridity and less fertilehabitats during the late Pleistocene (Ayliffe et al.,1998; Bowler et al., 2001; Field et al., 2002; Packet al., 2003), there are very few examples linkingearly human artifacts directly to megafauna(Roberts et al., 2001a). One source of confusionhas been that important archaeological sites suchas Lake Mungo and Koonalda Cave have yieldedmeager faunal data. Cuddie Springs, New SouthWales, is the only site in Australia that showsevidence of a dated association between humantechnology and megafauna (Dodson et al., 1993).Fossil bone exhibiting human processing markswere dated to 36-27 ka (Field & Dodson, 1999).However, the association between the artifactsand megafauna remains was questioned byRoberts et al. (2001a) who suggested: 1) thatsediment mixing and re-deposition of bones fromolder to younger units had occurred, and 2) thecut marks on the bones relate to an extant speciesof kangaroo. Although there is little systematicevidence to suggest an anthropogenic component

to Australian megafauna extinction, Flannery(1990) argued that because of the rapid nature ofan overkill ‘blitzkrieg’ extinction, kill sites areunlikely to be found. Additionally, timing thearrival of the first humans and extinction of themegafauna has been impeded by a lack of reliabledates (Baynes, 1999; Diamond, 2001; O’Connell& Allen, 2004). On the Darling Downs, there isno evidence of human occupancy prior to 12ka(Gill, 1978). From sedimentological andecological data, it is evident that increasingaridity on the Darling Downs during the latePleistocene may have led to woodland and vinethicket habitat contraction, and grasslandexpansion on the floodplain. Such habitat changewas likely detrimental to the persistence ofmegafauna species on the Darling Downs duringthe late Pleistocene. However, at present there isno direct evidence to support a hypothesis of ananthropogenic component relating to theretraction of habitats on the Darling Downsbetween the Pleistocene and present.

CONCLUSIONS

Systematic collecting targeting both large andsmall-sized species has facilitated the recovery ofa wide variety of fossil taxa, many previouslyunknown in the Darling Downs fossil record.First Pleistocene Darling Downs records include:pulmonates (7 terrestrial species, 1 aquaticspecies), Tympanocryptis “lineata”, scincids (4species), and Sminthopsis sp. Additionally,several of those new records indicate Pleistocenegeographic range extensions.

It has been assumed that the PleistoceneDarling Downs represents a single local faunawith no faunal regionalisation (Molnar & Kurz,1997). That may appear to be true for largermegafauna taxa, but the small-sized fossil faunasare poorly known at most sites owing to the lackof systematic treatment. Hence, additionalsystematically collected and dated sites arerequired to test the hypothesis proposed byMolnar and Kurz (1997), that the Darling Downsrepresents a single local fauna.

The habitats deduced for the time of depositionof Horizon D appear to be more floristicallycomplex than that of Horizon B. However,analysis of the Pleistocene channel deposits haverevealed several taphonomic biases relating tothe preservation of large- and small-sized taxawithin and between those horizons. Such biaseslimit palaeoenvironmental comparisons betweenthose two units.


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It is evident that there was major habitat changein the Kings Creek floodplain post-deposition ofthe two major fossiliferous horizons atQML1396. That habitat change likely reflectedthe contraction of woodlands, vine thickets andscrublands, and expansion of grasslands on thefloodplain. Sedimentological and ecological datasuggest that that habitat change was climaticallydriven and occurred irrespective of potentialhuman occupation of the region during the latePleistocene.

ACKNOWLEDGMENTS

We thank Gregg Webb, Alex Cook, Liz Reedand Troy Myers for valuable comments anddiscussion on earlier drafts of this manuscript.Bernie Cooke, Scott Hocknull, Liz Reed andBrendan Brooke are thanked for helpfuldiscussions and comments on various aspects ofDarling Downs palaeoenvironments. MatthewNg, Ricky Bell, Philip Colquhon, Luke Shipton,Kristin Spring, Trevor Sutton, Diane and AmySobbe, and Desmond and Jennifer Price,provided much needed support and assistance inthe collection and preparation of fossil material.John Stanisic and Scott Hocknull providedidentifications for the molluscs and agamidsrespectively. The AMS14C dating component ofthe study at ANSTO was supported by grantsfrom AINSE (Grant no’s. 02-013 & 03-123). Thiswork was funded in part by both the QueenslandUniversity of Technology and the QueenslandMuseum.

LITERATURE CITEDANDREWS, P. 1990. Owls, Caves and Fossils. (Natural

History Museum Publications. London).APLIN, K.P. & ARCHER, M. 1987. Recent advances in

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Paper 4. PRICE, G.J. & WEBB, G.E. in press. Late Pleistocene sedimentology,



This chapter presents a comprehensive stratigraphic, sedimentologic, and

taphonomic analysis of a late Pleistocene Darling Downs fossil deposit at site

QML796. Those investigations allowed additional development of

hypotheses relating to Darling Downs megafaunal extinction. This chapter

represents a preprint of an article submitted for consideration in Australian

Journal of Earth Sciences (2005 © Geological Society of Australia).

Australian Journal of Earth Sciences is available online at:

http://journalsonline.tandf.co.uk/openurl.asp?genre=journal&issn=0812-0099.




Acknowledgements). I also supervised that laboring efforts of the volunteers

who assisted in the preparation of fossil material. I measured stratigraphic

sections, collected sediment samples, and carried out grain size analyses.

Additionally, I conducted all subsequent taphonomic analyses and prepared

the original and final manuscripts for submission.

Gregory E. Webb guided the sedimentological analyses and assisted in

the development of ideas and interpretation of the deposits. His role in

manuscript preparation was primarily editorial.

125

Late Pleistocene sedimentology, taphonomy and megafauna extinction on

the Darling Downs, southeastern Queensland, Australia

Gilbert J. Price and Gregory E. Webb

School of Natural Resource Sciences, Queensland University of Technology,

GPO Box 2434, Brisbane, Queensland, Australia 4001

[email protected]

Phone: (07) 3406 8350

Mobile: 0439 876 005

Fax: (07) 3406 8355

Suggested running title: Darling Downs megafauna deposits

126

ABSTRACT

The Kings Creek catchment, southeastern Queensland, contains a variety of

Pleistocene-Holocene depositional settings. Fluvial depositional accumulation

processes in the catchment reflect both high-energy channel and low-energy

episodic overbank deposition. The lithofacies and depositional environments of

locality QML796 were examined in detail to aid interpretation of taphonomic

accumulation patterns of large and small taxa in the deposit. The basal

fossiliferous unit was deposited in a meandering channel and passes upward

into overbank deposits that include ephemeral interfluve channels and splays.

The most striking taphonomic observations for vertebrates at the locality

include: 1) low representation of post-cranial elements; 2) high degree of bone

breakage; 3) variable abrasion but most identifiable bone elements with low to

moderate degree of abrasion; 4) low rates of bone weathering; and 5) low

degree of articulated or associated specimens. Collectively, those data suggest

that the material was transported into the deposit from the surrounding proximal

floodplain and that the assemblages reflect substantial hydraulic sorting.

However, despite that, sequential faunal horizons show a step-wise decrease in

taxonomic diversity that cannot be explained by sampling or taphonomic bias.

The decreasing diversity includes loss of some, but not all, megafauna and is

consistent with a progressive local loss of megafauna in the catchment over an

extended interval of time. Data are consistent with a climate change model for

megafauna extinction but not with nearly simultaneous extinction of megafauna

as required by the human-induced blitzkrieg extinction hypothesis.

Key words: fluvial sedimentology, taphonomy, Darling Downs,

Queensland, Australia, megafauna extinction, Pleistocene.

INTRODUCTION

Our understanding of current threats to biodiversity and the prospects for

survival of extant species is informed by palaeoecology, and in particular,

knowledge of previous extinction events. Although mass extinction events have

been documented throughout the Phanerozoic, one of the most relevant, but

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least well understood, intervals of species loss occurred near the end of the

Pleistocene, i.e., the extinction of terrestrial megafauna.

The late Cainozoic witnessed the evolution and subsequent extinction of

some of the largest land animals (lizards, birds and mammals) that the world

has known. In Australia, 88 % of Pleistocene terrestrial taxa with average

weights in excess of 44 kg became extinct before the end of the epoch

(Barnosky et al., 2004). Causes for extinction have been debated widely with

climate change, human hunting and/or agricultural practise, or a combination of

those factors being the dominant hypotheses (for recent reviews see Horton,

2000; Barnosky et al., 2004; Wroe et al., 2004; Burney & Flannery, 2005).

Testing such hypotheses has proven difficult, and in Australia in particular, the

lack of a spatially constrained chronology for the extinction of individual species

and for human occupation renders many hypotheses almost impossible to test.

Roberts et al. (2001) suggested that the last Australian megafauna occurred at

~46.4 ka, but their sampling procedures and subsequent interpretations have

been strongly criticised (Field & Fullager 2001; Wroe et al., 2004). Aside from

the fact that the 46.4 ka date falls near the limit of effective radiocarbon dating

(Gillespie, 2002), Roberts et al. (2001) analysed only deposits that contain

articulated remains of megafauna. Although the sampling strategy was aimed at

limiting the possibility of reworking of older megafaunal remains into younger

deposits, it automatically excludes the majority of known late Pleistocene

megafauna sites, including, for example, most archaeological sites (e.g., Field &

Fullagar, 2001). Many such sites have been dated younger than 46.4 ka (e.g.,

Cuddie Springs; Field & Dodson, 1999; Roberts et al., 2001; Trueman et al.,

2005). The stratigraphic integrity and provenance of fossils from younger

deposits may be questioned (Baynes, 1999), but reworking cannot be assessed

on the basis of dating alone (Field & Fullagar, 2001; Trueman et al., 2005).

Specific hypotheses of reworking can be tested by using data from disciplines

such as taphonomy, sedimentology, geochemistry, archaeology and

geomorphology, to independently establish the context and accumulation

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processes of a fossil deposit (e.g., Behrensmeyer, 1988; Lyman 1994; Trueman

et al., 2005).

Unfortunately, few studies have specifically investigated the depositional

processes and taphonomic modes of fossil accumulation of Australian

megafauna deposits (e.g., Baird, 1991; Long & Mackness, 1994; Van Huet,

1999; Brown & Wells, 2000). Hence, spatial and temporal constraints on the

palaeoecology of prehistoric Australian terrestrial communities are poorly

known, especially including those that encompass late Pleistocene megafauna

extinction. Studies that document taphonomic modes of bone accumulation are

particularly relevant in that they can aid recognition of reworking and bias

related to both accumulation processes and preservation. Bias in the fossil

record may affect diversity estimates, timing of extinction events, and analysis of

palaeobiological and palaeoenvironmental parameters (Behrensmeyer, 1988;

Lofgren et al., 1990). Many processes influence the progression of bones from

the living animal to their final place of burial and preservation, including activity

by carnivores, pre-burial weathering, hydraulic transport and abrasion,

diagenesis, and the accumulation mode itself (i.e., processes that cause sorting

in specific depositional environments) (Voorhies, 1969, Dodson, 1971; 1973;

Behrensmeyer, 1975; 1978; 1982; 1988; Haynes, 1980; 1983; Andrews, 1990;

Lyman, 1994). Hence, taphonomic processes must be considered in order to

constrain palaeoecological inferences based on fossil assemblages.

Vertebrate accumulations from deposits such as those in caves are generally

considered to be of high value for interpreting past environmental conditions

because remains typically are not transported far or reworked and mixed

vertically (Andrews, 1990; Baird, 1991). However, more abundant deposits from

fluvial depositional environments commonly have much more complicated

depositional histories, both temporally and spatially. Hence, fluvial environments

hold greater possibilities for mixing local faunas with contemporaneous faunas

transported from distant environments or with older fossils reworked from

eroding deposits (Behrensmeyer, 1988). However, faunal associations from

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such deposits are capable of yielding useful information on past environmental

conditions provided they are carefully documented and analysed.

Some of the youngest known Australian Pleistocene megafaunal remains

have been recovered from fluvial deposits in the Kings Creek catchment in the

Clifton region of the Darling Downs, Australia (Roberts et al., 2001). Late

Pleistocene vertebrate remains from the Kings Creek area range from

articulated skeletons to disarticulated and highly fragmented, abraded remains

and occur in low-energy overbank deposits at QML783 (Molnar et al., 1999) and

in high-energy channel deposits and lower-energy, episodic overbank deposits

at site QML1396 (Price & Sobbe, 2005). Importantly, the Pleistocene catchment

size is constrained by regional drainage divides and was very small in area

(Price, 2005), probably not much larger than the present catchment (~500 km2)

(Figure 1). Thus, faunal remains represent local Pleistocene environmental

conditions. Price and Sobbe (2005) described the depositional environment of

the vertebrate-bearing site QML1396 (Figure 1) and concluded that a lower

fossiliferous horizon was deposited as a high-energy channel fill, whereas a

higher horizon was deposited in an overbank setting as crevasse splay

deposits. The ecologies of the faunal assemblages from the two horizons

suggested that woodland and vine-thicket habitats contracted as open

grasslands expanded between deposition and European arrival in the region.

Radiocarbon dating of the horizons yielded dates of 44.3-49.9 ka (Price &

Sobbe, 2005), near the limits of effective dating. Interestingly, the lower channel

deposits contain diverse megafaunal remains, whereas megafaunal diversity is

greatly reduced in the upper horizon. Unfortunately, it could not be determined if

the rarity of megafauna in the upper horizon was due to local extinction or to a

bias in accumulation due to differential sorting during deposition of the overbank

deposits (Price & Sobbe, 2005). Regardless, the site shows evidence of

changing faunal composition, which may reflect changing habitat, between the

two horizons, and megafauna clearly became extinct some time subsequent to

deposition of the upper fossiliferous horizon.

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Figure 1. Modern Kings Creek Catchment with heights (metres) of surrounding peaks, the main

study locality (site QML796), and other localities mentioned in the text (GDR: Great Dividing

Range; KCC: Kings Creek Catchment; QML: Queensland Museum Locality).

The purpose of this paper is to describe the sedimentology and taphonomy of

vertebrate remains from site QML796, located in the northern bank of Kings

Creek, ~200 m downstream from site QML1396. Fossil remains at site QML796

include more than sixty species ranging in size from small invertebrates to

megafauna (e.g., Diprotodon sp.) and occur in at least three highly fossiliferous

horizons, at least one of which appears to be younger than both fossiliferous

horizons studied at site QML1396. Thus, the site can provide data to test the

hypothesis that megafauna became extinct in a single event in the Kings Creek

catchment. Site QML796 was excavated from the top down so as to record

stratigraphic data and bone orientation, and >24 m3 of sediment were sieved to

recover both large and small remains. The small catchment size combined with

detailed excavation and sieving techniques provides an opportunity to

investigate sedimentologic and taphonomic controls on the accumulation of

remains of large- and small-sized taxa from in situ stratigraphic horizons that

131

could bracket the extinction of some megafauna on the Darling Downs. Such

analyses are crucial for interpreting fossil-based palaeoecological information,

thereby providing data for testing specific hypotheses about the causes of

megafaunal extinction in Australia.

SETTING

The Darling Downs, southeastern Queensland, Australia, encompasses the low

rolling hills and plains west of the Great Dividing Range (Figure 1). Site QML796

(Figure 1) was discovered on the northern bank of Kings Creek by Mr. Ian

Sobbe of Clifton in the early 1980s. The initial exposure was ~6-7 m in diameter

with a 2.3 m-thick fossil bearing horizon. The modern Kings Creek catchment is

fed from the east by shallow, ephemeral watercourses, and is bounded to the

north, east and south by the topographically high Great Dividing Range (Figure

1). On the basis of regional topographic constraints, Price (2005) suggested that

Pleistocene fossil material deposited in the catchment is unlikely to have been

sourced from geographic areas outside the modern catchment (i.e., from

distances greater than 20-25km to the east). Early collecting at site QML796

was sporadic, generally focusing on recovery of larger megafaunal taxa.

Systematic collecting of the deposit by the Queensland Museum (QM)

commenced in 2000, and a diverse small-sized fauna was recovered (Price

2002, Price et al., 2005). More recently, joint excavations by the Queensland

University of Technology (QUT) and QM have focused on the collection of

stratigraphic, sedimentologic, and taphonomic data from the deposit.

The poorly indurated sediments of the Darling Downs consist of clay, silt and

sand derived from the erosion of underlying Mesozoic sandstone and Tertiary

basalt (Woods, 1960; Gill, 1978); previous stratigraphic studies were described

by Price and Sobbe (2005). The exact age of Darling Downs fossil deposits is

poorly constrained. Gill (1978) dated fossiliferous deposits near Talgai,

Queeensland using radiocarbon techniques and obtained dates of 41.5-23.6 ka

for charcoal, 20.17-6.45 ka for molluscs, and 30.8-4.42 ka for carbonate

nodules. Price (2005), Price and Sobbe (2005), and Price et al. (2005) reported

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accelerator mass spectrometry (AMS) radiocarbon dates from charcoal and

fossil bivalves for QML796 and QML1396 of 49.9-40 ka. Roberts et al. (2001)

dated site QML783 (= ‘Ned’s Gully’; Figure 1) to ~47 ka based on optically-

stimulated luminescence (OSL). Hence, deposits in Kings Creek are most likely

late Pleistocene.

METHODS

Excavation and Sedimentology

The early QM excavation involved the documentation of seven main

stratigraphic units (designated A1 to A7) from top to bottom. Fossils were

recovered from an exposed vertical section by in-situ collecting and removal of

bulk sediment to target smaller specimens. All fossil material was labelled

according to the sedimentary horizon from which it was derived, and >10 m3 of

sediment were processed.

More recent QUT-QM excavations involved a ‘top down’ excavation

approach. A 3x2 m plot was surveyed on the ground above the site, and 1x1 m

quadrats were excavated in 10 cm increments using trowels and brushes.

Excavated layers were correlated to stratigraphic units on the vertical sides of

the pit. The excavation continued to the depth of 2.3 m yielding an additional

~14 m3 of material. Orientations of freshwater bivalves (Velesunio ambiguus)

and bones larger than 2 cm were recorded in-situ. The attitude (i.e., concave- or

convex-up) of V. ambiguus valves was also documented. Excavated sediment

was washed using graded sieves (10 and 1mm), and small bones were sorted

following techniques described by Andrews (1990). The manual sieving and

sorting was particularly labour intensive, with museum volunteers contributing

>15 000 hours of labour.

The entire exposed section was measured and documented on vertical

surfaces during excavation. Sediment samples from each stratigraphic unit were

disaggregated using alternating cycles of bleach and detergent, dried, and

sieved using –2 to 4 phi mesh sizes for grain size analysis. A 2.3 metre-long

auger was used to probe surrounding sediment to determine the lateral extent

133

of particular beds. Lithofacies and fluvial architectural elements were identified

and assigned facies codes following the technique described by Miall (1996).

Taphonomic Analysis

Identifiable cranial and post-cranial material of terrestrial vertebrate species

provided the basis for the taphonomic study. Unidentifiable bone fragments

were not used. The unit of element representation includes MNI (minimum

number of individuals; equivalent to NISP [number of identified specimens]

following Badgely, 1986), and MNE (minimum number of elements; Lyman,

1994). For vertebrates, identification of taxa was based mostly on dentary and

maxillary remains, except in the case of fish, frogs, turtles and some

squamates, where vertebrae, pelves, carapace/plastron fragments and

osteoderms were used, respectively. We conducted rarefaction analyses using

the PAST © statistical software (Hammer et al., 2001) on taxon abundance data

for each assemblage to test for potential bias introduced by differences in

sample sizes. Diversity patterns using the rarifed data sets were compared

between assemblages of standardised subsample sizes with independent

Kolmogorov-Smirnov two-sample statistical tests (Jamniczky et al., 2003;

Payne, 2003). Additionally, taxon abundance data from each assemblage were

combined, and bootstrapping analyses (1000 replicates with resampling) were

conducted using PAST © to obtain 95% confidence intervals for the estimate of

N taxa in a given assemblage.

The colour of all bones used in the taphonomic study was documented.

Other bone surface features relating to root etching, bacterial action, pH

corrosion, and calcrete encrustation were also noted. The relative degree of

weathering of the bones was determined following criteria of Behrensmeyer

(1978; Table 1), and each element was assessed for abrasion using a

descriptive scale adapted from Spencer et al. (2003; Table 2).

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Table 1. Bone weathering stages (following Behrensmeyer, 1978).

Stage Character

0 No signs of weathering

1 Bone surface cracking

2 Deep cracking and flaking of bone surface

3 Large patches of rough, compact bone

4 Bone surface fibrous, exhibiting splintering

5 Bone falling apart in-situ, large splinters missing with deep

cracking

Mammal skeletal relative abundance was calculated using the equation:

( )EiMNINi

Ri100×= (1)

where R is the relative abundance of element i, N is the minimum number of

element i, MNI is the minimum number of individuals, and E is the expected

number of element i in a skeleton (Andrews, 1990). Determination of E was

based on comparison with modern mammal skeletons. The equation allows

comparison of numbers of different skeletal elements that occur in varying

proportions in mammalian skeletons.

Table 2. Abrasion stages of fossil bone (modified from Spencer et al., 2003).

Abrasion stage Characteristics

Absent Absent

Minimal Slight erosion to one or two points on bone

Light <25% of bone surface exhibits erosion

Moderate 25-50% of bone surface exhibits erosion

Heavy 50-75% of bone surface exhibits erosion

Extreme >75% of bone surface exhibits erosion

Cranial and dentary breakage patterns of large (>5kg) and small (<5kg)

mammals were identified in the deposit following the techniques of Andrews

(1990) and Price and Sobbe (2005; Figures 2, 3). Identification of post-cranial

breakage patterns of major limb bones (humeri, ulnae, femora, tibiae) followed

Andrews (1990). Broken limb bones were classified as proximal, shaft, or distal

135

portions. The percentage of representation for each breakage pattern was

calculated to determine potential differences between large- and small-sized

mammal skeletal breakage within and between horizons.

Figure 2. (a-g) Mammal cranial breakage categories from the QML796 assemblage (shaded

areas indicates the preserved portions).

Identification of the taphonomic agents responsible for bone fracturing can

provide significant information about the formational history of an assemblage

(Shipman et al., 1981; Villa and Mahieu, 1991). Bone fractures were classified

into one of eight main fracture patterns that commonly occur in fossil

assemblages (Figure 4; adapted from Marshall, 1989; Reed, 2003).

Figure 3. (a-l) Mammal dentary breakage categories from the QML796 assemblage (shaded

areas indicates the preserved portions).

Indices of taphonomic modification patterns of vertebrates in the deposit

mostly were derived from Andrews (1990), and their specific applications were

as described by Price and Sobbe (2005). Indices calculated include: percent of

136

post-crania to crania; percent of distal element loss; percent of fore limb loss;

percent molar tooth loss; and relative loss of molar tooth sites, as an

independent index of cranial breakage (Kos, 2003).

Figure 4. Stylised distal portion of a macropod femur indicating bone fracture patterns. (a)

Stepped. (b) Crenulated. (c) Spiral; (d) V-shaped. (e) Smooth perpendicular. (f) Irregular

perpendicular. (g) Longitudinal. (h) Impact.

Bone modification by carnivores includes a range of different tooth marks.

For example, rodents produce characteristic parallel tooth markings through

gnawing (Lyman, 1994), whereas larger carnivores generally crush bone by

static loading, which produces consistent breakage patterns (Johnston, 1989).

Sobbe (1990) identified ten categories of tooth markings on fossils from

Pleistocene deposits of the Darling Downs (Table 3), and tooth markings on

bones from QML796 were classified based on comparison to those examples.

Each identified bone also was scored with respect to the number and position of

tooth marks.

The degree of hydraulic sorting experienced by the accumulations was

determined by comparing the relative abundance of elements to experimental

results from studies by Voorhies (1969), Dodson (1973), Behrensmeyer (1975),

and Korth (1979).

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Table 3. Characteristics of tooth markings on fossil bone that commonly occur in Darling Downs

deposits (following Sobbe, 1990).

Tooth marking Characteristics

Round bottom scratches with

anchor point

Series of closely spaced near parallel scratches;

characteristic of rodents

Blade-like impressions Long blade-like impressions to 27mm long, V-shaped in

cross section; characteristic of Thylacoleo

Crescent-shaped markings Bone surface displaced at right angles to long axis leaving

ridge of semi-attached bone at concave edge

Pits and scratches Pits round to oval to diameter of 2mm; round bottomed

scratches parallel to walls with corrugations at right angles

to long axis marks

Large deep scratches Scratches to 27mm long, 5mm wide

Fine scratches tapered at

both ends

Fine, round bottomed scratches with widest point near

middle, tapering to both ends

Round punctures Round punctures depressing compact bone surface, 3-

3.5mm in diameter; similar to Sarcophilus.

Large oval punctures Large oval punctures to 14mm long, 7mm wide

Spongy bone removal with

depressed punctures

Depressed punctures 5-8mm diameter on articular ends of

long bones

Ragged edges and hollow-

backed edges

Bone with ragged edges and associated depressions of

bone edge; attributed to carnivore gnawing

In situ bivalve taphonomy was evaluated using the coexistence index of left

and right valves (Cv) of V. ambiguus. Cv was calculated using the equation:

1

211V

VVCv

−−= (2)

where V1 is the greater number of valves and V2 is the lesser number of valves

(after Shimoyama & Hamano, 1990). Cv values range between 0 and 1 and

measure the deviation from the expected 1:1 ratio. Additionally, χ2 tests were

computed to test for preservation differences between bivalves.

Other statistical analyses were performed using SPSS © statistical software.

Correlations were considered to be significant at the 95% confidence level.

138

Figure 5. Murid age classification scheme based on M1 tooth wear. (a) Young. (b) Adult. (c)

Mature.

Faunal attributes

Vertebrate mortality profiles were determined for murids and macropods. The

age structure classification for murids was based on the degree of tooth wear of

the M1 (Figure 5). Age structure classification of larger (>5 kg) macropods was

determined using molar eruption patterns following criteria in Table 4.

Body weights of extant and extinct vertebrate taxa were derived from Hecht

(1975); Murray (1991), Strahan (1995), and Wroe et al. (2003a, b).

Table 4. Age class characteristics for macropods based on premolar and molar eruption

patterns, modified from Reed (2003).

Age class Eruption sequence

Pouch young dp2, dp3, M1 erupting

Young dp2, dp3, M1, M2 erupting

Juvenile dp2, dp3, M1-2, M3 erupting

Sub-adult dp3, M1-M3, M4 erupting (M1 & M2 worn)

Adult P3, M1-M4 (M1-3 worn)

Mature M1-M4 (all molars worn)

Senile M2-4 (molars worn)

RESULTS

Sedimentology and Stratigraphy

Stratigraphy of the deposit was determined to be more complex than was

documented in the earlier excavation, but we retain original QM stratigraphic

139

nomenclature for the main fossiliferous horizons (A7, A4 and A1) to be

consistent with pre-existing collections. The deposit is characterised by

alternating coarse- and fine-grained siliciclastic sediment, mostly arranged into

individual fining-up cycles or couplets of coarser and finer sediments with a

single coarsening-up unit near the top (denoted C1-C8; Figure 6). Fine-grained

horizons contain abundant smectite clays as evidenced by cracking behaviour in

the excavation (Figure 7). Vertebrate material occurs in each horizon, but is

most abundant in coarser units. In general, freshwater bivalves (V. ambiguus

and C. (C.) australis) and thiarid gastropods (T. (P.) balonnensis) are most

abundant in coarse horizons, but some fine-grained horizons contain scattered

shelly lenses with abundant T. (P.) balonnensis. Elongate fossil material is

generally oriented within 10° of horizontal. Fine-grained units contain rare

calcrete rhizocretions.

Figure 6. Measured section of QML796 (stratigraphic column D; see also figure 8) indicating

coarsening upward cycles and original QM nomenclature.

140

The base of the section is generally below the modern watertable and

consists of crudely bedded siltstone and claystone (Fsm), mudstone (Fm), and

interlaminated mudstone and laminated sandstone (Fl) (Table 5; lithofacies

codes of Miall, 1996). The fine-grained rocks are overlain by a very coarse to

coarse, fining-up sandstone unit (0.7-1.3 m) containing scour-fill sand (Ss) at

the base passing upwards into massive sand (Sm) (C1 on Figure 6). The basal

contact represents the highest order erosion surface in the section, and the

deposit is laterally extensive, being recorded 50 m upstream and 70 m

downstream from the excavation (Figure 8). The unit is equivalent to the ‘lower’

A7 horizon of the QM excavation. Freshwater mollusc and vertebrate fossils are

abundant along with reworked, rounded pebbles of calcrete and rarely, basalt,

at the base. The orientation of fossil bivalves (V. ambiguus) and long bones

shows a strong east-northeast to west-southwest trend (Figure 9a) and 50% of

V. ambiguus valves occur with their anterior portion directed to the eastern

quadrant (i.e., between NE and SE; Figure 9a). Both conjoined and non-

conjoined V. ambiguus are most abundant within the C1 sands, and a high

percentage of valves occur in hydrodynamically unstable positions. The top of

the C1 sandstone passes into Fm through most of the excavation, but the base

Table 5. Lithofacies classification and description (adapted from Miall, 1996).

Lithofacies code Description

Fsm Massive to crudely bedded siltstone and claystone

Fm Massive mudstone

Fl Interlaminated mudstone and laminated sandstone

Ss Scour-fill sand

Sm Massive sand

Sh Horizontal laminated sand

Sl Low-angle bedded sand

141

Figure 7. Stratigraphic exposure of site QML796. (a) Photograph of outcrop. (b) Line drawing of

stratigraphic units indicating fluvial architectural elements. See table 6 for definition of codes.

of the overlying C3 sandstone Ss rests directly on C1 sandstone to the north

(Figures 6-8). Lithofacies Ss of C2 pinches out against the base of C3 to the

north, but is otherwise separated from C1 and C2 by Fsm (Figures 6-8). The

combined C2-C3 cycles collectively represent the ‘upper’ A7 horizon of the QM

excavation. Long bones and bivalve shell orientations in C2 and C3 exhibit a

142

northwest to southeast trend (Figure 9b), and 40% of V. ambiguus valves occur

with anterior portions directed to the eastern quadrant (Figure 9a).

Figure 8. Fence diagram of consistent stratigraphic units at site QML796. (a) Plan view of

stratigraphic columns indicating position of detailed QUT-QM ‘top-down’ excavation (columns C-

E). (b) Stratigraphic columns. See table 6 for fluvial architectural element code definition.

Laterally extensive, crudely horizontally bedded Fm overlies the upper C3

sand and is overlain to the north by three stacked, fining-up, very coarse Ss and

horizontally bedded sand (Sh) units that pass upward into Fl (C4-C6; Figures 6-

8). The coarse units represent the A4 horizon of the QM excavations and do not

persist to the south, where they have been truncated against a scour surface.

The sands contain few internal structures other than fine lamination and contain

abundant mollusc and vertebrate remains, but lack the coarser pebbles and

cobbles that characterise the base of C1. Bivalves and long bones are oriented

east to west, and ~54 % of V. ambiguus valves occur with their anterior portion

directed to the eastern quadrant (Figures 9c & 10a).

143

Figure 9. Orientations of bone and large bivalves (Velesunio ambiguus) from QML796. (a) A7

‘lower’ horizon. (b) A7 ‘upper’ horizon. (c) A4 horizon. (d) FF between A1 and A4 horizons. (e)

A1 horizon.

The C6 sand passes into laterally persistent, crudely bedded to massive Fsm

and Fm. To the south this fine unit clearly lies above a scour surface that has

removed C4-C6, but no coarse lag occurs above the scour contact in the

excavation (Figures 6-8). The base of the overlying C7 unit also represents a

broad scour surface. The base of C7 consists of Ss and Fl with crude horizontal

bedding. The deposit is laterally discontinuous and thins to the west. Freshwater

molluscs are abundant, but vertebrate fossils are rare. Bivalves and long bones

from the coarse and fine C7 horizons show no obvious trend in orientation, but

~39 % of V. ambiguus valves occur with anterior portions directed to the eastern

144

quadrant (Figure 10a). The C7 sand passes into massive to crudely bedded

Fsm and Fm up section.

The highest coarse unit is the base of C8 (Figure 6). The deposit consists of

crudely laminated, coarsening-up, coarse to very coarse sand (Sl) with crude,

low-angle (<15o) accretion surfaces and a broad scoured base. The sand is

discontinuous to the north and south and thins to the west (Figure 8).

Freshwater molluscs and vertebrate fossils are abundant. Orientation of V.

ambiguus and long bones shows a strong northwest to southeast trend.

Approximately 54% of V. ambiguus valves occur with anterior portions directed

to the eastern quadrant (Figure 10a). The base of C8 is synonymous with the

A1 horizon of the QM excavations. Overlying fine-grained deposits are Fm that

has been disturbed by modern soil formation and agriculture. There is no

evidence that modern soil processes disturbed the underlying stratigraphy

documented above.

Figure 10. Characteristics of large-sized, in-situ bivalves (Velesunio ambiguus) from QML796.

(a) Orientation of anterior portion of valves. Error bars indicate binomial 95% confidence

intervals. (b) Frequency of single valves in hydraulically unstable positions and frequency of

conjoined bivalves.

145

INTERPRETATION

Four main fluvial architectural elements (sensu Miall, 1996) were identified in

the deposit (Table 6). The base of the section is interpreted as floodplain fines

(element FF) on the basis of massive to crudely horizontally bedded Fm, Fl and

Fsm.

Table 6. Fluvial architectural element classification and description (adapted from Miall, 1996).

Element Code Description Constituent lithofacies

FF Overbank fines Fm, Fl, Fsm

LA Lateral accretion Ss, Sm

CH Channel Ss, Sh

CS & CR Crevasse splay and channel Ss, Sl

The coarse parts of cycles C1-C3 (A7 horizon) represent lateral accretion

(LA) elements and consist of channel lag or channel bar deposits. The lack of

preserved channel margins in C1 precludes distinguishing between a channel

lag and a bar. However, the wide lateral extent and fining-up nature of C1 within

a floodplain fines-dominated sequence is consistent with a point bar. The

coarse sands of C3 may represent a small channel lag based on the lateral

pinching character (Figures 7, 8). The lower LA deposit (C1) represents higher

velocity currents than subsequent horizons based on the significantly coarser

grain size near the base and high order scoured base and is interpreted to have

been deposited in a main channel. The high proportion of V. ambiguus valves

preserved in hydraulically unstable positions in the lower portion of C1 may

represent deposition in deeper scour pools amongst coarse sediment. Current

direction is difficult to determine based solely on bone orientation. Long bones

orient parallel with the current in high velocity flow with the heavier ends

upstream, but may orient perpendicular to the current flow at lower velocities

(Behrensmeyer, 1990). The common fragmentation of bone with loss of heavier

146

ends in C1 complicates the issue. However, the orientations of V. ambiguus

shells provide evidence for current direction. Experimental and field results on

similarly shaped bivalves indicate that valves preferentially orient with their long

axis parallel to the flow and with their anterior ends up-current (Nagle, 1967).

Additionally, Brenchley and Newall (1970) suggested that if unidirectional

orientations of bivalves were observed in transported assemblages, then the

portion of the shell closest to the centre of gravity would be directed up-current.

For single V. ambiguus valves the centre of gravity is closest to the anterior end.

The common anterior orientation of valves in C1 to the eastern quandrant

(Figure 10a) suggests that flow was generally from east to west, which is

consistent with data from long bones and predicted flow direction based on the

modern catchment.

The succeeding LA elements (C2 and C3) were minor in comparison to C1,

and each passes upwards into lithofacies Fm, Fsm, and Fl that are interpreted

as element FF. The erosion of C3 into the top of C1 and lateral pinch-out of C2

within the excavation suggests reactivation of an abandoned channel in an

ephemeral system. C2 and C3 sands are not interpreted as levee deposits

owing to their pinching and erosive nature and separation from each other and

from C1 by FF. Combined bone and shell orientation data indicate

palaeocurrent direction for C2-C3 was from southeast to northwest. Minor

differences in flow orientation between C1 and C2-C3 (Figure 9) may reflect

channel migration over time in the ephemeral system, but all flow was basically

east to west. As the Pleistocene floodplain was geographically small, it is

unlikely that Fm deposits within the FF element represent in-channel mud

drapes, which are common in larger, sandy ephemeral channel systems where

waning flood deposition allows the settling of fines (e.g., Best et al., 2003). No

fluvial flaser-like structures were observed (e.g., Martin, 2000). The wide lateral

extent and considerable vertical variability of the FF deposits and abrupt

transitions to thin channel deposits is more consistent with a low relief

depositional surface that is susceptible to minor changes in depositional

processes (Miall, 1996). Scattered shelly lenses in the FF deposits are

147

consistent with episodic overbank deposition, and bone and shell orientation

data do not indicate significant palaeocurrent trends in the fine horizons.

The sands of C4-C6 are interpreted as stacked minor channel elements (CH)

owing to their laterally restricted occurrence, fining–up grain size, and enclosure

in FF deposits. Deposition probably occurred in minor tributaries on the

interfluve during high rainfall periods, with at least three main depositional

phases preserved. Combined bone and shell orientation data indicate that

palaeocurrent direction was from east to west. The CH deposits pass upwards

into a thick section of FF but were eroded away to the south beneath a scour

surface. Any lag deposits associated with the scour do not crop out in the

excavation, suggesting that the truncation of C4-C6 was located relatively high

on the shoulder of the eroding channel.

Coarse sands at the bases of C7 and C8 are interpreted as crevasse splay

(CS) and crevasse channel (CR) deposits, respectively (Figure 7). Element CR

was defined by the concave-up, scoured channel floor and likely proximity to a

main channel based on content of coarse reworked bone clasts. Internal scour

and fill structures between accretionary units indicate multiple episodes of

erosion and sedimentation. Bone and shell palaeocurrent direction data indicate

southeast to northwest flow. Both C7 and C8 thin to the west indicting

progradation onto the floodplain. The CR element of C8 exhibits low-angle

accretion surfaces recording growth by lateral accretion within the channel, and

the coarsening-up pattern is consistent with progressive erosion deepening the

breach during flooding.

Collectively, the point bar, flashy discharge features, scour surfaces, and

abundant abrupt lithofacies shifts between Sh, Sl, Fm, and Fl suggest that site

QML796 represents ephemeral channel deposits and overbank fines in a

meandering stream system (Miall, 1996). That interpretation is supported by the

ecology of the abundant V. ambiguus. Extant populations are generally

associated with low velocity creeks and billabongs, rarely occurring in large,

high-velocity rivers (Sheldon & Walker, 1989). Larger-sized unionoids with

elongate, ‘winged’ shells, such as Alathyria spp., are more commonly

148

associated with permanent high-velocity rivers, but were not identified in the

Kings Creek deposits.

Stratigraphic correlation within Kings Creek catchment

The C1 LA deposit of QML796 can be lithologically and biostratigraphically

correlated to the basal channel deposit of QML1396 (Horizon B of Price &

Sobbe, 2005) (Figure 11). Site QML1396 represents a basal channel deposit

passing upwards into overbank deposits (Price & Sobbe, 2005). The basal

channel deposit is laterally extensive, fines upwards and has abundant

freshwater molluscs and vertebrate fossils. It occurs at approximately the same

elevation with respect to the modern watertable as C1 at QML796. Thicker (~9

m) overlying FF deposits at site QML1396 contain alternating Sl and Fm with

desiccation cracks, mottled calcrete and Fe nodules.

Figure 11. Stratigraphic relationships between QML796 (stratigraphic column D) and QML1396.

Site QML783 (= ‘Ned’s Gully’ in Molnar, et al., 1999; Roberts et al., 2001), in

the southern bank of Ned’s Gully, Kings Creek catchment, was interpreted as

an overbank abandoned flood channel deposit (Figure 1; Molnar et al., 1999).

Articulated and associated specimens are abundant. Molnar et al. (1999)

149

suggested that there was no bias in species size represented in the deposit as

both large- and small-sized mammals were recorded. The low degree of

scattering of skeletal material may indicate rapid burial by slumping of an

unstable gully wall (Molnar et al., 1999). Tufa was subsequently found at the site

suggesting a possible spring deposit, but was not collected in situ. Regardless,

the absence of freshwater molluscs indicates that the deposit was not a main

watercourse during the period of deposition (Molnar et al., 1999). Stratigraphic

relationship of QML783 to sites QML796 and QML1396 remains unclear.

Bivalve Taphonomy

Cv values indicate that a disproportionately high number of single left valves of

V. ambiguus were preserved in the deposit (A7: Cv = 0.62, N = 379; A4: Cv =

0.52, N = 229; A1: Cv = 0.66, N = 103). Single left valves contributed 60-65% of

all non-conjoined V. ambiguus valves within each main fossiliferous horizon (A7:

χ2 = 19.97, df = 1, σ = <0.001; A4: χ2 = 22.01, df = 1, σ = <0.001; A1: χ2 =

4.28, df = 1, σ = 0.039). Non-conjoined valves generally occurred in

hydraulically stable positions (i.e. concave down; Brenchley & Newall, 1970), but

single valves dipping between 20o and vertical to concave up (i.e., unstable)

positions were most common in A7 (Figure 10b). Conjoined bivalves were twice

as abundant in A1 as in other horizons (Figure 10b).

INTERPRETATION

Bivalves generally disarticulate after death with initial ratios of preserved left and

right valves generally near 1:1 (i.e., Cv = 1) at the source spot (Shimoyama &

Fujisaka, 1992) where the probability of preserving complete and undamaged

conjoined shells is highest (Cadée, 1968). The low Cv of V. ambiguus at

QML796 indicates transport from the original source spot, which is consistent

with a flashy, ephemeral discharge regime. The left-right sorting phenomenon of

bivalves and brachiopods during transport has been documented in marine

environments (Martin-Kaye, 1951; Boucot et al., 1958; Johnson, 1960; Behrens

& Watson, 1969) but not in non-marine environments. Low Cv values in marine

150

environments generally reflect minor differences in the hydrodynamic properties

of left and right valves, even where valves are bilaterally symmetrical. However,

bivalves in marine environments are generally exposed to a greater variety of

currents and swashing effects than are bivalves in uni-directional currents in

most low-velocity water courses. Random walk simulations of shell diffusion can

produce low Cv’s in marine environments with statistically small samples

(Shimoyama & Fujisaka, 1992). However, Cv approaches unity with larger

sample sizes. Regardless, Cv values decrease with increasing distance from

the source spot. Hence, the QML796 bivalves probably experienced significant

transport from their source spots. The Cv values are closer to unity for the A1

horizon, which also has the highest proportion of conjoined bivalves (Figure

10b), and are lowest for A4, which has the lowest proportion of conjoined

bivalves (Figure 10b). Thus, the source spot for A1 bivalves may have been

closer to the final point of deposition than for A7 and A4, which is consistent

with A1 representing a splay deposit and A4 and A7 representing channels.

Vertebrate Taphonomy

Fossil material is unequally distributed through the deposit. Fossils recovered

from FF deposits are poorly preserved and markedly less abundant than fossils

in coarser-grained horizons. Due to the paucity of fossil material in the fine-

grained horizons, taphonomic inferences are based on fossil material recovered

from the coarser-grained horizons (A7, A4 and A1). Few meaningful data could

be obtained from the tens of thousands of small (generally <20 mm),

unidentifiable bone fragments that represent differing stages of preservation,

weathering and abrasion, and that range from angular bone shards to rounded

bone pebbles. Thus, the taphonomy discussed below was based on identifiable

species and/or skeletal elements.

BONE APPEARANCE

Fossil bone colours range from creamy-white, brown, brown-red, to black,

representing variable degrees of mineralisation. Brown-red bones were more

151

common in A4 and A7 than in A1, but no definitive trend in colour was identified.

Root etching of bone surfaces was uncommon (<1%) in each horizon, and

where present, generally affected less than 5% of the bone surface. There was

no observed evidence of pH-related or bacterial etching (e.g., Chaplin, 1971) on

any fossil material from the deposit. Calcrete encrustations on bone are

relatively uncommon but are slightly more abundant in the A1 horizon.

The majority of identifiable specimens from the deposit represent weathering

stages 0-2, showing either no weathering or some cracking and exfoliation of

the outermost bone surface (Figure 12) (criteria of Behrensmeyer, 1978). For

large-sized mammals, A1 exhibits the highest proportion of unweathered bone

(Figure 12a). Horizon A7 exhibits the highest degree of weathered bone and the

only material in weathering stage 3 (Figure 12a). Small-sized mammal material

is generally within weathering stage 0 (Figure 12b).

Figure 12. Weathering of bone from QML796. (a) Large-sized mammals. (b) Small-sized

mammals. See table 1 for definition of weathering stages. Error bars indicate binomial 95%

confidence intervals.

152

FAUNAL ATTRIBUTES

Species recovered from the deposit are listed in tables 7 and 8. In terms of

abundance and diversity, mammals dominated the terrestrial faunal component

in each horizon (Tables 7 and 8). At the family level, murids were the most

common group in each horizon. Several groups are rare in the assemblage,

including birds, monotremes, vombatids (wombats), and palorchestids

(marsupial tapirs). Other groups were recovered from only one horizon (e.g.,

potoroids in A4) or were represented by single specimens (e.g., thylacinids in

A4).

Table 7. MNI (minimum number of individuals) of non-mammalian taxa for main fossiliferous

horizons at QML796 (excluding bivalves and Thiara (Plotiopsis) balonnensis). * indicates species

recorded solely by abraded material.

Class Family Species A7 A4 A1

Gastropoda Planorbidae Glyptophysa gibbosa - 1 -

Gyraulus gilberti 131 133 58

Punctidae Paralaoma caputspinulae 1 1 -

Charopidae Coencharopa sp. 2 6 2

Gyrocochlea sp. 5 29 9

Rhytididae Strangesta sp. - - 1

Succineidae Austrosuccinea sp. - 1 1

Osteichthyes (Teleostei)

? Teleost gen. et. sp. indet. 94 152 96

Anura Myobatrachidae Limnodynastes tasmaniensis 1 4 4

L. sp. cf. L. spenceri - 1 -

Kyarranus sp. 1 - -

Reptilia Chelidae Chelid gen. et sp. indet. 4 20 4

Agamidae Tympanocryptis lineata 19 31 16

Physignathus leseurii 44 1 3

153

Table 7 continued

Scincidae ‘Sphenomorphus Group’ sp. 1 2 4 5

‘Sphenomorphus Group’ sp. 2 2 6 6

‘Sphenomorphus Group’ sp. 3 - 3 -

Tiliqua rugosa 4 20 7

Varanidae Varanus sp. 3 1 3

Megalania prisca 52 51 58

Elapidae Elapid gen. et sp. indet. 6 37 17

Crocodylidae Crocodylid gen. et. sp. indet. 2 4* 1*

Aves ? Aves gen. et sp. indet. - - 6

Anatidae Anatid gen et. sp. indet. sp. 1 - 1 -

Anatid gen et. sp. indet. sp. 2 - 1 -

Rallidae Gallinula mortierii - - 1

Casuriidae Dromaius novahollandiae 1 1 1

TOTAL 374 509 299

Analytical rarefaction data tend towards an asymptote for each of the

assemblages at site QML796 (Figure 13a). Although the A4 horizon

assemblage contained the most samples, the observed biotic diversity

decreased from A7 (44 taxa) to A4 (39 taxa) and from A4 to A1 (33 taxa) based

on a subsample number of 705 individuals following rarefaction (Figure 13a).

Kolmogorov-Smirnov independent two sample tests comparing the rarified

curves indicated that the A7 and A4 assemblages were not significantly different

(z = 1.06; σ = 0.206). However, the A1 assemblage was significantly less

diverse than both A7 (z = 4.36, σ = <0.001) and A4 (z = 3.40, σ = <0.001).

Hence, sampling cannot account for the observed patterns of diversity. A

bootstrap analysis was applied to test whether the sampled assemblages were

derived from the same initial community, thus testing the null hypothesis that the

observed decrease in diversity (i.e., possible local extinctions) was caused by a

154

synchronous event that occurred some time after deposition of the A1 horizon.

Bootstrap analyses indicated that the observed diversity of A7 and A4 fit within

the 95% confidence boundaries predicted based on the original sample sizes

(Figure 13b). However, the observed diversity of A1 fell below the lower

predicted 95% confidence boundary (Figure 13b), suggesting that the

assemblage was derived from a different, less diverse biotic community than

were A7 and A4.

Figure 13. Diversity measures for QML796. (a) Rarefaction curves for assemblages. (b)

Bootstrap results for assemblages indicating predicted diversity (95% confidence intervals) and

observed results.

Diversity was also compared between the lithologically equivalent units at

QML796 (A7 horizon) and QML1396 (Horizon B). The abundance data of

equivalent taxa was rarified, and Kolmogorov-Smirnov tests based on

standardised subsample sizes (16 individuals) indicated that the diversity was

not significantly different (z = 1.06, σ = 0.211). Additionally, with the exception of

a single Thylacinus cynocephalus specimen, a carnivorous species that is

generally rare in Darling Downs fossil deposits, there are no taxa represented in

155

the basal channel unit of QML1396 that are not also represented in the LA

deposit of QML796. The overall more diverse faunal assemblage of QML796

probably reflects more intensive sampling at QML796 than at QML1396.

Table 8. MNI (minimum number of individuals) of mammalian taxa for main fossiliferous horizons

at QML796. * indicates species recorded solely by abraded material.

Class Family Species A7 A4 A1

Mammalia Ornithorhyncidae Ornithorhyncus anatinus - 1 -

Tachglossidae Tachyglossus sp. - 1 -

Zaglossus sp. 4 - -

Dasyuridae Dasyurid gen. et. sp. indet. 1 1 4

Sminthopsis sp. 2 2 1

Dasyurus sp. cf. D. viverrinus 5 13 7

D. vivverinus 1 4 4

Antechinus sp. - 1 -

Sarcophilus laniarius 2 - 5

Thylacinidae Thylacinus cynocephalus - 1* -

Peramelidae Peramelid gen. et. sp. indet. 7 15 11

Perameles sp. 1 6 1

P. bougainville 2 - -

P. nasuta 2 1 3

P. sobbei 6 5 6

Isoodon sp. - 4 -

I. obesulus 2 2 -

Vombatidae Vombatid indet. 3 2 1

Vombatus sp. - - 1

Phascolonous gigas 1 - -

Palorchestidae Palorchestes azael 1 - -

Palorchestes sp. 1 - -

156

Table 8 continued

Diprotodontidae Diprotodon sp. 26 42 2*

Zygomaturus trilobus 4 - -

Thylacoleonidae Thylacoleo carnifex 1 1 -

Potoroidae Bettongia sp. - 1 -

Aepyprymnus sp. - 3 -

Macropodidae Macropod gen. et. sp. indet. 26 112 33

Sthenurine gen. et. sp. indet. - 2 -

Sthenurus andersoni - 1* -

Troposodon minor 14 10 3*

Macropus sp. 22 3 1

Macropus sp. A - 1 -

M. agilis siva 18 18 -

M. titan 7 11 4

M. pearsoni - - 1*

Protemnodon sp. 14 18 2

Pr. brehus 1 8 1

Pr. roechus 3 7 -

Pr. anak 19 12 3

Muridae Murid gen. et. sp. indet. 387 905 478

Ps. gracilicaudatus 4 - -

Ps. australis 18 20 4

Pseudomys sp. A - 1 -

Rattus sp. (close to R. tunneyi

or R. sordidus)

8 6 7

Hydromys chrysogaster 2 2 1

TOTAL 615 1243 584

157

The percentage of non-aquatic taxa representing different body weights at

QML796 indicates that small-sized taxa dominated each assemblage and were

slightly more common in A1 (Figure 14). Additionally, the A1 horizon had only a

single taxon >100 kg, Megalania prisca. Taxa >100 kg were slightly more

abundant in A7 than in other horizons.

Figure 14. Body sizes of terrestrial vertebrate taxa from QML796. Error bars indicate binomial

95% confidence intervals.

Large-sized macropods were poorly represented in A1. Hence, mortality

profiles are based only on larger-sized macropods from A4 and A7 (Figure 15a).

Macropod age profiles for A4 and A7 are generally negatively skewed towards

younger individuals. Sub-adult individuals are most common in A7, whereas

mature adults are most common in A4. Mortality profiles show that murid

mortality was evenly distributed for the three age classes in A4 and A7 (Figure

15b). However, murid mortality was highest for young individuals and lowest for

aged individuals in A1.

SKELETAL PART REPRESENTATION

With the exception of molluscs, non-mammalian skeletal elements are poorly

represented at QML796 (Table 9). Where present, they are generally

represented by fragmentary material. Comparison of non-mammalian vertebrate

post-cranial elements (Table 9) to the MNI data (Table 7) indicates a high

relative loss of post-cranial skeletal material.

158

Tab

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7 A

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4 A

7 A

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4 A

7 A

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4 A

7 A

1 A

4 A

7 A

1 A

4 A

7 A

1 A

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1 A

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Max

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-

- -

- -

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- 9

17

10

1 2

- -

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- -

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Den

tarie

s -

- -

- -

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14

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12

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- -

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91

110

41

- -

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21

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48

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7 15

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1 1

159

Figure 15. Mortality profiles of mammals from QML796. (a) Macropods, excluding A1 individuals.

(b) Murids. See table 4 and figure 5 for definitions of age classes. Error bars indicate binomial

95% confidence intervals.

Cranial elements are the best represented elements of both large and small

mammals in each horizon (Figure 16). However, all skeletal elements are under-

represented in comparison to numbers of elements expected in complete

skeletons. For large-sized mammals, A4 has the highest relative abundance of

all skeletal elements. A1 is particularly devoid of large mammal material, with

maxillae and molars the only skeletal elements with greater than 6% relative

abundance. For small mammals, incisors are abundant in each horizon (>80%).

Small mammal post-cranial material is poorly represented in each horizon with

no element represented by greater than 10% relative abundance.

SKELETAL BREAKAGE

Large-sized mammal cranial material of A4 is more fragmentary than that of A7

and A1 (Figures 17-18). The only complete cranium (Diprotodon sp.) was

collected from the A7 horizon. No complete dentaries were recovered from any

horizon, and maxillae and dentaries of large mammals are rare in A1. Thus,

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comparisons of large mammal maxillae and dentary breakage patterns were

restricted to A4 and A7 (Figures 17-18). Large mammal dentaries from A4 are

Figure 16. Skeletal relative abundance of mammals from QML796. (a) Large-sized mammals;

(b) Small-sized mammals.

more fragmentary and exhibit a wider range of breakage patterns than A7 large

mammals. For small mammals, dentaries lacking the inferior border of the

horizontal ramus were the most abundant breakage pattern identified in each

horizon. Small mammal maxillae were more completely preserved in A7.

Of the major limb bones, the number of complete elements is very low for

both large and small mammals (Table 10). Moderate proportions of complete

specimens occur for all post-cranial elements (Figure 19), but robust elements

(calcania, phalanges and unguals) represent 48-98 % of those complete

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Figure 17. Frequencies of cranial breakage patterns of mammals from QML796. (a) Large-sized

mammals. (b) Small-sized mammals. See figure 2 for illustrations of breakage patterns. Error

bars indicate binomial 95% confidence intervals.

specimens. Due to relatively low abundance of post-cranial remains, breakage

trends between horizons could not be confidently assessed (Table 10).

Proportions of fracture patterns of post-cranial material show that fracture

patterns of dry or fossilised bone, particularly transverse fractures (fracture

pattern F), make up the majority of specimens in each horizon for both large

and small mammals (Figure 19). Green type fractures, although rare, are slightly

more common in A4 and A7 than in A1 (Figure 19).

Skeletal modification indices suggest that there was a significant loss of post-

cranial skeletal material for both large and small mammals within each horizon

(Table 11). Proximal limb elements (femora and humeri) are more abundant

than distal elements (tibiae and radii) for large and small mammals in horizons

A1 and A4. The ratio of distal to proximal elements is approximately 1:1 for

large and small mammals in A7. Forelimb elements (humeri and radii) are less

represented than hindlimbs (femora and tibiae) for large- and small-sized

mammals of A1 and large-sized mammals of A4 and A7. Hindlimbs are slightly

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better represented than forelimbs for small-sized mammals in A4 and A7. Large

numbers of isolated molars occur in each horizon, associated with molar tooth

site losses (Table 11).

Table 10. Breakage of major post-cranial limb elements from QML796.

Limb bone <5kg mammals >5 kg mammals

A1 A4 A7 A1 A4 A7

N (%) N (%) N (%) N (%) N (%) N (%)

Humerus

complete 0 (0.0) 4 (44) 3 (16) 0 (0) 7 (17) 0 (0)

proximal 15 (50) 0 (0) 1 (5) 0 (0) 6 (15) 2 (20)

shaft 10 (33) 4 (44) 9 (47) 1 (50) 8 (19) 1 (10)

distal 5 (17) 1 (12) 6 (32) 1 (50) 20 (49) 7 (70)

Femur

complete 3 (17) 4 (17) 1 (10) 1 (33) 4 (11) 0 (0)

proximal 12 (67) 2 (9) 4 (40) 1 (33) 18 (49) 7 (78)

shaft 2 (11) 16 (70) 2 (20) 1 (33) 3 (8) 0 (0)

distal 1 (5) 1 (4) 3 (30) 0 (0) 12 (32) 2 (22)

Ulna

complete 0 (0) 0 (0) 0 (0) 0 (0) 1 (7) 0 (0)

proximal 2 (29) 5 (63) 2 (50) 0 (0) 10 (67) 5 (84)

shaft 1 (14) 1 (12) 2 (50) 0 (0) 2 (13) 1 (16)

distal 4 (57) 2 (25) 0 (0) 0 (0) 2 (13) 0 (0)

Tibia

complete 1 (4) 0 (0) 0 (0) 1 (50) 0 (0) 0 (0)

proximal 6 (26) 3 (14) 2 (7) 0 (0) 3 (27) 2 (14)

shaft 1 (4) 17 (81) 12 (86) 1 (50) 5(46) 2 (14)

distal 15 (66) 1 (5) 1 (7) 0 (0) 3 (27) 10 (72)

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Table 11. Skeletal modification indices for small- and large-sized mammals from QML796.

Skeletal modifications < 5kg mammals > 5kg mammals

A1 A4 A7 A1 A4 A7

Post-cranial element loss 29.63 21.02 28.22 20.00 67.50 42.11

Distal element loss 63.3 18.4 92.9 66.7 75.0 105.9

Fore limb loss 58.1 114.8 105.9 25.0 32.4 66.7

Molar tooth loss 786.7 660.0 603.4 725.0 271.4 116.1

Molar tooth site loss 186.7 155.8 355.2 100.0 694.7 567.7

Figure 18. Frequencies of dentary breakage patterns of mammals from QML796. (a) Large-sized

mammals. (b) Small-sized mammals. See figure 3 for illustrations of breakage patterns. Error

bars indicate binomial 95% confidence intervals.

CARNIVORE MODIFICATION

Carnivore or scavenger markings on bone are rare (<3%) for horizons A7 and

A1. V-shaped grooves with associated depressed fractures (sensu Sobbe,

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1990) are the only type of tooth markings observed on A7 fossil bone. Fine

scratches and crescent-shaped markings (sensu Sobbe, 1990) are the only type

of tooth markings observed on A1 fossil bone. Carnivore markings are more

abundant and diverse on A4 fossil bones (N = 32, ~8%; Figure 20a). V-shaped

blade markings are the most common carnivore markings (Figure 20b) and are

commonly associated with depressed punctures. Limb bones are the most

abundant skeletal element containing tooth markings (Figure 20c), with those

tooth markings generally confined to the shaft (Figure 20d).

Figure 19. Fracture patterns of mammal skeletal elements from QML796. (a) Large-sized

mammals. (b) Small-sized mammals. See figure 4 for definition of fracture patterns. Error bars

indicate binomial 95% confidence intervals.

ABRASION AND HYDRAULIC SORTING

Abrasion was absent in 45-61 % of identifiable large-sized mammal specimens

(Figure 21a). A1 exhibits the lowest proportion of unabraded large mammal

specimens, and the highest proportions of heavily and extremely abraded

skeletal material. Small-sized mammal material is largely unabraded in all

horizons (Figure 21b).

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Figure 20. Carnivore tooth markings of bone from the A4 horizon at QML796. (a) Frequency and

degree of tooth marked bone. (b) Frequency of types of markings observed. (c) Frequency of

skeletal elements with tooth markings. (d) Frequency of the positions of tooth markings on limb

elements. See table 3 for definition of tooth mark categories. Error bars indicate binomial 95%

confidence intervals.

Comparison of relative abundance data of skeletal elements for mammal

species to experimental data (Voorhies, 1969; Behrensmeyer, 1975; Dodson,

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1973, Korth, 1979) (Figure 22) suggests that skulls and maxillae of large

mammals are poorly represented in the deposit. However, the majority of

elements recorded represent those elements that are transported in the middle

to middle-late categories of fluvial transport. For small mammals, skeletal

elements are dominated by those that are transported in the middle-late

category of dispersal. Elements that are among the first to be transported by

flowing water are uncommon for both large and small-sized mammals.

Figure 21. Degree of abrasion of mammal skeletal material from QML796. (a) Large-sized

mammals. (b) Small-sized mammals. See table 2 for definition of abrasion stages. Error bars

indicate binomial 95% confidence intervals.

ARTICULATED AND ASSOCIATED MATERIAL

Only three examples of articulated and associated material were observed in

the deposit. An associated Protemnodon sp. calcaneum and cuboid were

collected from the thin coarse layer (2280-2330 mm) just below the A1 horizon

(Figure 23a). They were separated by approximately 15 mm and matched each

other well.

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Figure 22. Percent relative abundance of skeletal elements from QML796 aligned with

comparative results of skeletal element transportability in hydraulic systems. (a) Large-sized

mammals, following Voorhies (1969) and Behrensmeyer (1975). (b) Small-sized mammals,

following Dodson (1973) and Korth (1979) (I, early transported elements; I/II, early-middle; II,

middle; II/III, early-late; III, late).

An associated Macropus titan left pelvis, femur, tibia and calcaneum were

recovered from A4 (1780-1880 mm; Figure 23b). The specimens were

associated on the basis of size, proximity to each other, and age of the

individual; the femur and tibia were missing their proximal and distal epiphyses

indicating that the individual was a sub-adult. An additional Macropus sp. cf. M.

titan humerus missing the proximal and distal ends was collected from the same

depth. The specimen compares well for size with the associated elements, but

could not be associated with confidence.

Several skeletal elements of a single water dragon (Physignathus leseurii)

individual were recovered during sieving of bulk sediments from the A7 horizon.

The individual is represented by 18 cranial and dentary elements, 18 vertebrae,

and 8 other post-cranial elements. Considering the high proportion of the

skeleton collected, and tendency for squamate cranial and post-cranial

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elements to disarticulate readily after death, the specimen may have been

articulated.

Figure 23. Associated skeletal material from QML796. (a) Protemnodon sp. calcaneum and

cuboid from the small coarse layer below the A1 horizon (2280-2330mm). (b) Macropus titan left

pelvis, femur, tibia and calcaneum from the A4 horizon (1780-1880mm). Shaded bones indicate

associated material.

Taphonomic interpretation

The abundance of unidentifiable, small, broken bone fragments is consistent

with a fluvial setting, and highly abraded, rounded bone pebbles suggest

multiple episodes of reworking and transport within the confines of the small

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catchment. Taphonomic interpretations are based on identifiable fossil bone so

as to yield more palaeobiological and palaeoecological information, but it is

recognised that some components of the assemblage may have had different

taphonomic pathways leading to their final deposition, including reworking from

older deposits. The focus on better preserved material allows independent

conclusions regarding the probability of reworking to be drawn for specific

specimens. The critical task is to differentiate between ecologic and taphonomic

bias as the causes of observed trends in diversity and abundance.

Low pH-etching of fossil material is considered not to have biased

preservation at QML796 owing to: 1) the occurrence of calcrete, both in situ in

FF and as reworked clasts, throughout the deposit; 2) abundant well preserved

mollusc shells; and 3) the general lack of acid-etched bone. Patterns of bone

abundance probably reflect other taphonomic processes. The greater degree of

calcrete encrustation on fossil material from the A1 horizon may reflect its

relatively high position above the watertable and seasonally dry climate. Minimal

root etching of fossil material suggests that stable vegetation with deep root

systems may not have been permanently established over the deposit in most

recent times due to the on-going erosion and semi-regular filling of the

abandoned channels. Price and Sobbe (2005) concluded that the catchment

hosted increasing levels of shallow-rooting grasses at the expense of deeper

rooting shrubs and trees subsequent to deposition of the basal sequence at

nearby QML1396.

BIAS RELATING TO FAUNAL GROUPS

In modern Australian faunal communities, marsupials, birds, frogs, turtles, and

snakes are most diverse in the continental margin regions where rainfall is

greatest, whereas lizards tend to be more diverse in arid inland areas (Pianka &

Schall, 1981). However, in all bioregions, birds and lizards dominate vertebrate

communities in terms of diversity, being 10-30 times and 2-10 times more

diverse than marsupials, respectively (Pianka & Schall, 1981). However, the

diversity of vertebrate groups at QML796 differs markedly, with marsupials

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dominating. Such a result probably reflects a variety of taphonomic and ecologic

factors. Generally, the most common identifiable elements of non-mammalian

vertebrate taxa in QML796 are maxillae, dentaries, vertebrae, and osteoderms

(Table 9). All other cranial and post-cranial elements are poorly represented.

For reasons discussed above, preferential dissolution of small-sized bones in

acidic soils is unlikely to have caused the bias. Unfortunately, few studies have

addressed the causes of such bias, instead focussing on mammalian

accumulation in fossil deposits. It has been assumed that the remains of non-

mammals accumulate via similar taphonomic pathways to mammals (Martin,

1999), and that may be true for larger groups such as dinosaurs (Dodson,

1971). However, that may not be the case for smaller non-mammalian terrestrial

vertebrates (Behrensmeyer, 1975). Differences in preservability and

transportability of non-mammalian groups such as squamates and birds may be

attributed to hydrodynamic and/or density related factors (Vickers-Rich, 1991;

Behrensmeyer et al., 2003), but additional research is required in order to better

understand the exact taphonomic processes involved.

Several groups of mammals are uncommon in the deposit, possibly reflecting

their rarity in the living community. For example, monotremes, vombatids,

palorchestids and potoroids are uncommon at QML796 and constitute only

minor components of most other Australian Pleistocene vertebrate assemblages

(Molnar & Kurz, 1997; Murray, 1991; 1998; Reed & Bourne, 2000) presumably

owing to palaeobiological factors such as having had small standing

populations, solitary habits, and/or occupation of proximal versus distal habitats.

The rarity of Sarcophilus sp., Thylacinus cynocephalus and Thylacoleo carnifex

at QML796 is expected as they were carnivores (Molnar & Kurz, 1997). Other

groups that are absent in the Darling Downs fossil record (e.g., possums,

koalas) are rare in other Australian fossil deposits, reflecting their arboreal

habits (Murray, 1991).

Certain species recorded in the assemblage are represented solely by

abraded material. Abrasion on all bone surfaces is consistent with fluvial

transport (Shipman, 1981), but there is a paucity of experimental data to aid

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determination of the duration or velocity of transport. Hence, it is only possible

to conclude that non-abraded bone is unlikely to have been subjected to

substantial transport over considerable distances. Within QML796, the single

Macropus pearsoni specimen (isolated molar) from A1 is moderately abraded,

suggesting that it was significantly transported prior to deposition. Additionally,

Diprotodon sp. and Troposodon minor are represented only by severely abraded

material within A1. Thylacinus cynocephalus and Sthenurus andersoni are

represented solely by abraded material within A7 and/or A4. As long-distance

transport can be ruled out in the catchment, such specimens may have been

reworked from older deposits, thus being abraded in lags on different occasions.

Hence, they may not be coeval with other taxa in their respective horizons.

Body size distributions of species indicate that larger-sized taxa are slightly

proportionally more abundant in A7, and small-sized taxa are proportionally

more abundant in A1. Hypotheses to explain those differences in body size

representation include: 1) larger-sized species were missed during sampling in

the upper units; 2) bias against accumulation of large-sized taxa occurred during

deposition of the A1 horizon; and 3) geographic range changes (i.e., local

megafauna ‘extinctions’) of large-sized taxa occurred between the time of

deposition of A7 and A1.

Hypothesis 1 is rejected because each horizon experienced the same

intensive sampling; it is unlikely that larger-sized taxa were missed preferentially

in the upper units. Additionally, rarefaction analysis suggests that observed

diversity does not reflect sampling bias. The absence in horizon A1 of taxa such

as Thylacoleo carnifex, which has a MNI of 1 in both horizon A7 and A4, could

result from its initial rarity (e.g., Signor & Lipps, 1982), but the large species

Diprotodon sp. has a MNI of 26 in A7, and 42 in A4. The occurrence of only two

abraded Diprotodon specimens in horizon A1 is unlikely to reflect sampling bias,

but may represent reworking of older bones into that horizon. Regardless, many

large-sized taxa appear to be absent from horizon A1 for reasons other than

sampling bias.

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Hypothesis 2 relies on sedimentological and taphonomic data for testing.

Bones act as sedimentary particles in fluvial systems and are sorted according

to their settling velocities and hydrodynamic characteristics (Behrensmeyer,

1975). Settling velocities are related to bone size and density. For example, a

Protemnodon molar with a 3.1 cm3 volume has a hydraulic equivalence of a 10

mm quartz spheroid, and a Protemnodon metatarsal (93 cm3 volume) and

Diprotodon molar (70 cm3 volume) both have hydraulic equivalences of large

gravel (Behrensmeyer, 1975). Coarse-grained horizons, such as A7, would be

expected to contain larger-sized bones (and taxa) than finer-grained horizons on

the basis of fluvial sorting alone. However, apart from basal lags, overall mean

grain sizes for each of the fossiliferous horizons are not significantly different

(Figure 6), and all assemblages are dominated by small-sized individuals. As

current velocities capable of sorting and concentrating large bones would have

removed most of the smaller bones, the occurrence of both together attests to

the variability of flow regime and episodic nature of deposition. Regardless, the

A4 horizon sampled adult individuals of very large-size taxa such as Diprotodon,

so it would be expected to have had the potential to sample other very large-

sized taxa such as Zygomaturus (~500 kg), Palorchestes (~300 kg) or

Phascolonous (~150 kg). However, unabraded skeletal remains of those taxa

are absent from both A4 and A1. Similarly, unabraded material from adult

individuals of large-sized taxa occur in the A1 horizon, but they are limited to

Megalania prisca (~650 kg), Macropus titan (~85 kg), Protemnodon anak (~50

kg), and Pr. brehus (~75 kg). Thus, A1 also had the potential to sample large-

size taxa, such as Palorchestes, Troposodon minor (~45 kg), M. siva (~25 kg)

and Pr. roechus (~85 kg), but those taxa were recovered only from A7 and A4.

In the case of M. siva in particular, horizons A4 and A7 both had MNI of 18, but

no specimens were identified in A1. Its absence is unlikely to be due to

hydraulic sorting. Hence, each main fossiliferous horizon appears to have had

roughly equal potential to sample similarly large-sized taxa, and hypothesis 2 is

not supported.

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Observed differences in body size distributions with loss of large-sized taxa

up section is more consistent with hypothesis 3, geographic range adjustments

or progressive local extinctions of species during the period of deposition. A

similar loss of large-sized taxa occurred from lower to upper coarse-grained

horizons at nearby QML1396, but in that case taphonomic data did not allow

exclusion of hydraulic sorting as the cause of the pattern (Price & Sobbe, 2005).

At QML796, hydraulic sorting would, if anything, limit the amount of reworked

large-sized material entering the crevasse channels and splays of horizon A1,

as the largest material in the bed load of the main channel might not be

transported high enough in the water column to reach the breach. Where such

reworked material did become entrained in a crevasse channel, it would be

deposited proximally, and that may explain the occurrence of the heavily

abraded Diprotodon material in A1.

MORTALITY PROFILES

The mortality curve for murids approaches that of a typical natural attrition

curve, where juveniles are the highest represented age class and seniles are

the least represented. However, for macropods within the A7 and A4 horizons, a

greater number of sub-adult to adult individuals were selected. Such age

frequency distributions suggest that some bias selected individuals in their

prime years of reproduction, possibly after breeding seasons where the stresses

relating to reproduction lead to malnutrition (Lyman, 1994). Similar observations

have been made for extant populations of some marsupial taxa such as

Antechinus (Strahan, 1995). However, such mortality patterns have not been

reported for extant macropods. Mortality profiles dominated by mature

individuals were reported for Mesembriportax acrae and Ceratotherium praecox

populations from Pliocene deposits of South Africa (Klein, 1982), and Macropus

sp. cf. M. rufogriseus populations from Pleistocene deposits of Australia

(Pledge, 1990). Klein (1982) suggested that the lack of juvenile M. acrae and C.

praecox individuals may reflect removal before burial due to carnivore or

scavenger feeding, but carnivore modification data for site QML796 discussed

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below are equivocal. Pledge (1990) explained the absence of younger M. sp. cf.

M. rufogriseus individuals by the fragility of their bones so that measurable

maxillae and dentaries were not preserved. However, the QML796

assemblages are dominated by very small-sized individuals (Figure 14) whose

skeletal elements were probably more vulnerable to destruction than

macropods, thus, differential preservability of large macropods of varying sizes

is not supported for QML796. The macropod mortality profiles of QML796 also

resemble those of Pleistocene diprotodontoids and macropods from Bacchus

Marsh, Lancefield Swamp, Reddestone Creek, and Spring Creek, eastern

Australia (Horton, 1984; Long & Mackness, 1994). Those mortality profiles were

explained by the loss of resources caused by a series of droughts (Horton,

1984). Populations were exposed to a combination of over-grazing and

waterhole tethering effects, initially removing vulnerable age classes (young and

senile), resulting in a population of mature individuals (Horton, 1984).

Sedimentologic data suggest arid periods in the late Pleistocene Kings Creek

catchment, and thus, droughts may explain the QML796 macropod mortality

patterns.

CARNIVORE MODIFICATION

The low abundance of tooth-markings on bone may partly reflect a taphonomic

bias wherein dry-type fractures, which are abundant in the assemblages,

possibly overprinted evidence of carnivore damage, thus rendering those bones

fragmentary and carnivore damage unidentifiable, and excluding them from

analysis. The abundance of V-shaped tooth markings with associated

depressed punctures, which are attributable to Thylacoleo carnifex (Horton and

Wright, 1981; Sobbe, 1990), indicates that T. carnifex was a major carnivore in

the catchment at the time of deposition. However, T. carnifex tooth-markings

were not recorded on fossil bone from the A1 horizon. All other tooth-markings

recorded may be related to feeding from other carnivorous species recorded in

the deposits including Megalania prisca, crocodylids, Sarcophilus laniarius,

Thylacinus cynocephalus and Dasyurus viverrinus.

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Horton and Wright (1981) showed that Thylacoleo tooth-markings most

commonly occur on ribs, leading to the suggestion that Thylacoleo was a

specialist internal organ feeder. However, tooth-markings at site QML796 occur

on most skeletal elements, including dentaries, scapulae, ribs, vertebrae,

pelves, major limb bones, and metatarsals, suggesting a more generalist

feeding behaviour for Thylacoleo. Additionally, as carnivores typically gnaw on

the ends of limb bones, the high representation of tooth markings on the shafts

may indicate that the lower density, meatier limb bone ends were lost due to

carnivore activity. Regardless, overall levels of carnivore activity were not high.

ACCUMULATION PROCESSES

The most striking taphonomic observations from the assemblages include: 1)

low representation of post-cranial elements; 2) high degree of bone breakage;

3) low to moderate degree of abrasion of identifiable bones; 4) low rates of bone

weathering; and 5) low degree of articulated or associated specimens. Low

representation of certain post-cranial elements is most easily explained due to

hydrodynamic sorting. Based on the experimental studies of Voorhies (1969),

Dodson (1973), Behrensmeyer (1975) and Korth (1979), the high relative

abundance of skeletal elements that are transported in the middle to middle-late

categories of fluvial transport (Figure 22) and uncommon occurrence of

elements that are easily dispersed in flowing water indicates that extensive

sorting resulted in lag-type accumulations of both large and small-sized

mammals in each horizon. The low representation of crania and high numbers

of isolated molars and loss of molar tooth sites within each horizon may reflect

high susceptibility to breakage and destruction of crania. Such breakage is

consistent with sedimentologic data indicating deposition of the main

fossiliferous horizons during high velocity flow events. However, the velocity

required to transport skeletal material of small mammals is significantly lower

than that required to transport large mammals (Dodson, 1973), and such

elements may be transported as suspension load. Hence, differences in small

mammal skeletal representation also may be a function of differential

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preservability and destruction of particular elements. The fragile nature of small

remains makes them highly vulnerable to destruction through weathering and

abrasion in comparison to remains of larger-sized mammals in similar

environments.

The hydraulic equivalence of larger bones in each main fossiliferous horizon

is estimated (after Behrensmeyer, 1975) to have been much greater than the

mean grain size (~2 mm) of the entombing sediments. Thus larger bones may

not have been transported far from a proximal death assemblage

(Behrensmeyer, 1975). The low degree of abrasion on identifiable bones also

reflects a short transport path. Weathering patterns of fossil bones (mostly

weathering stages 0-2) suggest little preburial exposure, although the exact

duration of bone exposure cannot be determined (Lyman and Fox, 1989), and

highly weathered bone may have been more susceptible to dry fracturing during

transport, thus biasing its distribution towards unrecognisable bone fragments.

The dominant dry or fossil-type fracture patterns of bones are not consistent

with breakage of fresh bone by trampling, carnivores, or hominids, but are

consistent with breakage during flood events.

Collectively, taphonomic data indicate that fossil material was accumulated

and transported into the deposit from the surrounding proximal floodplain, which

is consistent with the small Pleistocene catchment size (Price, 2005). Fossil

material was unlikely to have accumulated from distances greater than 20-25km

(Price, 2005). Additionally, although some material was undoubtedly reworked

from older deposits, the less abraded material is not likely to have been

reworked numerous times, and hence, probably dates from near the time of

deposition. The presence of articulated and associated remains indicates that at

least some components of the assemblage died within close spatial and

temporal proximity to the final site of deposition. Hence, analysed samples

broadly reflect a small Pleistocene catchment over averaged, but discrete,

sequential time intervals.

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DISCUSSION

Several different types of taphonomic accumulations occur within the Kings

Creek catchment, and include deposits between the extremes of the channel-

lag and channel-fill (i.e., overbank) taphonomic modes of Behrensmeyer (1988).

Channel-lag accumulations are characterised by: 1) deposition in lower parts of

channels or erosional troughs, 2) deposition of sand and gravel, 3) well-sorted

bone accumulations, 4) some abrasion on bone, with bone pebbles common, 5)

high fragmentation of bone, 6) rare association of skeletal parts, and 7)

orientation of long bones with the palaeocurrent (Behrensmeyer, 1988). Such

deposits are allochthonous and may represent accumulation from throughout a

catchment (Behrensmeyer, 1988). Channel-fill modes are characterised by: 1)

deposition in the upper parts of channels or interfluves, 2) fine-grained sediment

matrix, 3) poor sorting of bone sizes, 4) lack of abrasion, 5) low fragmentation,

6) common association of skeletal parts, and 7) variable alignment with

palaeocurrent (Behrensmeyer, 1988). Bone is generally not transported over

great distances and the assemblage represents a more autochthonous deposit

with respect to the channel (Behrensmeyer, 1988). Sites QML796 (A7) and

QML1396 (B) both have lower channel-lag type accumulations (Behrensmeyer,

1988). The A4 and A1 horizons of QML 796 are somewhat intermediate

representing small interfluve channels and crevasse splays, mainly in overbank

settings. Deposits at QML783 are more similar to Behrensmeyer’s (1988)

channel-fill mode of accumulation.

Price and Sobbe (2005) suggested that sequential changes in fauna through

stratigraphy at site QML1396 was possibly related to changing habitat in the

Pleistocene Kings Creek catchment, and that those changes reflected

increasing aridity through time. The loss of diversity observed at QML796 also

suggests a shift in fauna over the time of deposition. In particular, some

megafaunal taxa (e.g., Diprotodon sp., Troposodon minor, Macropus agilis siva)

appear to have become locally extinct between horizons A7 and A1. However,

Kolmogorov-Smirnov two sample tests and bootstrapping analyses reject the

hypothesis that a simultaneous extinction event occurred after deposition of A1.

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Hence, some megafauna became extinct below the A1 horizon whereas others

clearly persisted through the A1 horizon (e.g., Megalania prisca, Macropus titan,

Protemndon anak, P. brehus) only becoming extinct subsequently. Although

dating techniques may be equivocal for the site (Price & Sobbe, 2005), and

there are inadequate numbers of fossiliferous horizons to constrain rates of

species loss, the results clearly suggest minimally a two-stage local extinction of

megafauna. They are not consistent with a ‘blitzkrieg’ extinction model. Human-

induced cut markings and bone fracture patterns (e.g., spiral fractures) have not

been observed at QML796 or QML1396, and unconfirmed reports of cultural

artefacts in association with Darling Downs megafauna-bearing deposits

(Klaatsch, 1904) have not been verified subsequently. Charcoal is rare in the

deposits, suggesting that firing of the landscape, either anthropogenic or

natural, was insignificant in the region during the period of deposition. Thus

there is no direct evidence for human interactions with fauna in the Kings Creek

catchment.

One of the major factors that has lent support to the ‘blitzkrieg’ model of

extinction is that glacial-interglacial cycles have been operating for much of the

Pleistocene, yet most extinctions seem to be clustered near the time of the

latest Pleistocene glacial maximum, which is more or less coincident with the

arrival of humans in some areas (e.g., North America, Grayson & Meltzer, 2002;

Australia, O’Connell & Allen, 2004). However, in Queensland long-term records

from coastal lakes (e.g., 600ka on Fraser Island; Longmore & Heijnis, 1999)

suggest that although aridification was an ongoing process through the late

Pleistocene, different glacial maxima were associated with different degrees of

aridity. Significantly, the last glacial maximum was the most severe of those

recorded and was followed by very dry conditions in the Holocene (Longmore &

Heijnis, 1999). If those results are correct, it provides a rational explanation for

why extinctions might be concentrated around the last glacial maximum. The

last glacial maximum may have been uniquely severe in terms of aridity. The

arrival of humans may be coincidental, but there is no longer a requirement for

an additional external (i.e., human) agency to force latest Pleistocene

179

extinctions. Hence, as evidence of changing habitat types have been

documented at site QML1396, and sedimentologic and taphonomic data

suggest a seasonally arid climate (e.g., abundant calcrete formation in an

ephemeral fluvial setting, and drought-like macropod mortality patterns) at

QML796, the most parsimonious hypothesis is that megafaunal change at Kings

Creek was gradual and reflected changing habitats mostly likely associated with

intensifying aridification.

CONCLUSION

Site QML796 in Kings Creek catchment of the Darling Downs, Queensland

consists of late Pleistocene sediments that were deposited in both meandering

channel and overbank settings in an ephemeral fluvial environment. The site

contains three highly fossiliferous horizons, A7, A4, and A1, from base to top,

representing a laterally extensive point bar deposit, smaller, ephemeral

interfluve channels, and crevasse channel and splay deposits, respectively.

Calcrete, occurring both as reworked pebbles in channel lags and as

encrustations of bones in the uppermost horizons, suggests ongoing seasonally

arid conditions during the time of deposition. Despite being a fluvial deposit, the

site provides an ideal laboratory for examining temporal changes in local

Pleistocene faunas because: 1) the size of the Pleistocene catchment from

which taxa were sampled is well constrained and small (~500 km2), thus limiting

the degree to which samples could have been sourced by long distance

transport; 2) the site contains three stratigraphically sequential, highly

fossiliferous horizons with secure control on relative ages; and 3) the site was

excavated and processed in such a way as to target both large and small sized

taxa and to record relevant sedimentological data for taphonomic and

environmental analysis.

Results indicate decreasing taxonomic diversity for mammals in succeeding

horizons (ie., A7 through A1) that cannot be explained by sample bias or

sedimentological bias associated with fluvial accumulation or preservational

processes. The data are consistent with a local loss of certain megafaunal taxa

180

over the period of deposition (e.g., Diprotodon sp., Troposodon minor, Macropus

agilis siva). However, some megafaunal remains persisted to the youngest

horizon (e.g., Megalania prisca, Macropus titan, Protemnodon anak, P. brehus),

and Kolmogorov-Smirnov tests and bootstrapping analyses do not support the

hypothesis that all megafaunal taxa became extinct prior to deposition of the

youngest fossiliferous horizon. Hence, the data are consistent with a

progressive extinction of megafauna in the late Pleistocene Kings Creek

catchment. No evidence of human interaction with Pleistocene remains was

observed in the site or in other nearby sites (e.g., QML783 and QML1396). The

apparent progressive megafaunal extinction on the Darling Downs does not

support a sudden ‘blitzkrieg’ model resulting from human hunting. The gradual

demise of taxa at QML796 and evidence of seasonally arid conditions in the

section is most parsimoniously attributed to increasing aridity in southeastern

Queensland that culminated in an unusually severe arid interval associated with

the last glacial maximum (e.g., Longmore and Heijnis, 1999).

ACKNOWLEDGMENTS

We thank B. Cooke, I. Reid, S. Hocknull, B. Brooke, E. Reed, I. Williamson and

A. Cook for assistance and/or comments on earlier drafts of this manuscript. We

thank an anonymous reviewer, and especially D. Megirian, for significant and

constructive comments on an earlier version of this manuscript. R. Bell, S.

Hocknull, M. Ng, I. Sobbe, D. Sobbe, A. Sobbe, T. Sutton, and P. Tierney

provided tremendous assistance with excavations. P. Colquhon, P. Hamilton, G.

Jordan, L. Shipton, K. Spring, G. Todd, J. Wilkinson and countless volunteers

provided assistance in the preparation of fossil material. Additionally, D. Price,

J. Price, the Sobbe family, D. Turner, and M. Turner are thanked for their

continued support. This work was funded by the Queensland Museum and

Queensland University of Technology.

181

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190

Paper 5. PRICE, G.J. submitted. Late Pleistocene ecosystem dynamics,

habitat change, and species extinction on the Darling Downs, southeastern


Palaeoecology.

This chapter provides a comprehensive interpretation of late Pleistocene

Darling Downs palaeoenvironments, both at a single, well constrained

locality, and in a wider catchment perspective. An extensive dating analysis

complements the palaeoenvironmental component. Megafaunal extinction

hypotheses are proposed for the late Pleistocene Darling Downs. The paper

was submitted to Palaeogeography, Palaeoclimatology, Palaeoecology.




Acknowledgements). I also supervised the laboring efforts of the volunteers

who assisted in the preparation of fossil material. Additionally, I conducted all

palaeoecological analyses, prepared grants for funding the radiocarbon

dating component of the study, and prepared the original and final

manuscripts for publication.

191

Late Pleistocene ecosystem dynamics, habitat change, and species extinction

on the Darling Downs, southeastern Queensland, Australia.

Gilbert J. Price

Queensland University of Technology, School of Natural Resource Science,

GPO Box 2434, Brisbane, Queensland, Australia, 4001. Ph: 61 7 3406 8350;

Fax: 61 7 3864 2330; Email: [email protected]

Abstract

Several late Pleistocene fossil localities in the Kings Creek catchment,

Darling Downs, southeastern Queensland, Australia, were examined in detail to

establish an accurate, dated palaeoecological record for the region, and to test

human versus climate change megafauna extinction hypotheses. Accelerator

Mass Spectrometry (AMS 14C) and U/Th dating confirm that the deposits are

late Pleistocene in age, but the dates obtained from the two methods are not in

agreement. A multifaceted palaeoecological investigation involving the

identification of specific species ecologies, ecological analogues to modern

habitats and communities, and measurements of diversity, revealed significant

habitat change between superposed assemblages of site QML796. The basal

fossiliferous unit contained species that indicate the presence of a mosaic of

habitats including riparian vegetation, vine thickets, scrubland, open and closed

woodlands, and open grasslands during the late Pleistocene. Those woody and

scrubby habitats contracted over the period of deposition so that by the time of

deposition of the youngest horizon, the creek sampled a more open type

environment. Current evidence suggests that habitat changed on the late

Pleistocene Darling Downs during the same timeframe that megafauna and

non-megafauna experienced geographic range shifts (i.e., local extinctions).

Those data are consistent with a climatic cause of megafauna extinction, and no

specific evidence was found to support human involvement in the local

extinctions or in forcing the climate change. Better dating of the deposits is

192

critically important as a secure chronology would have significant implications

regarding the continent-wide extinction of the Australian megafauna.

Keywords: megafauna, extinction, climate change, Pleistocene, Darling Downs,

Australia.

1. Introduction

The late Pleistocene witnessed the global extinction of almost 100 genera of

large-sized terrestrial vertebrates, commonly termed the ‘megafauna’ (animals

>44kg) (Barnosky et al., 2004). Such extinctions were most dramatic in America

and Australia where 72-88% of all megafaunal taxa were lost (Barnosky et al.,

2004). Debate over the causes for the extinctions has become particularly

polarised in recent years, with several leading hypotheses being pursued. The

most popular hypotheses suggest either: 1) an anthropogenic component to the

extinctions, via overhunting (‘blitzkrieg’ or attritional overkill) or indirect habitat

modification (‘sitzkreig’) (Martin, 1984; Flannery, 1990; Miller et al., 1999; 2005;

Alroy, 2001; Barnosky et al., 2004; Brook and Bowman, 2004; Fiedel and

Haynes, 2004; Johnson and Prideaux, 2004; Prideaux, 2004; Wroe et al., 2004;

Johnson, 2005); 2) naturally driven climatic change (Graham and Lundelius,

1984; Horton, 1984; 2000; Grayson and Meltzer, 2003; Guthrie, 1984; 2003;

Shapiro et al., 2004), or 3) a combination of both (Field and Dodson, 1999;

Barnosky et al., 2004; Trueman et al., 2005). However, there currently is no

universally accepted hypothesis capable of explaining Pleistocene terrestrial

megafaunal extinctions.

In many regions, understanding the relationship between late Pleistocene

human colonisation, climate change and species extinction has been impeded

by the lack of reliable dates (Barnosky et al., 2004). Development of late

Pleistocene chronologies is difficult in regions such as Australia, because many

important events may have occurred just outside the practical limits of

radiocarbon dating (Gillespie, 2002). Suggested dates for human arrival In

Australia range anywhere from >100 ka (Wang et al., 1998), > 60 ka (Roberts

193

and Jones, 1994; Thorne et al., 1999), and 50-42 ka (Fifield et al., 2001;

Gillespie, 2002; Bowler et al., 2003; O’Connell and Allen, 2004), with most of

those dates obtained from optically stimulated luminescence (OSL), electron

spin resonance (ESR), U/Th or radiocarbon dating techniques. Roberts et al.

(2001) and Miller et al. (1999; 2005) developed chronologies of megafaunal

extinction using radiocarbon, amino acid racemisation (AAR), U/Th, and OSL

methods and suggested that most Australian megafauna extinctions occurred

synchronously and continent-wide at ~46 ka. However, a growing body of

evidence is beginning to demonstrate that some species persisted beyond the

hypothesised extinction window of 46 ka (Field and Dodson, 1999; Trueman et

al., 2005). Those data mostly suggest overlaps of at least 15 ka between human

arrival and megafaunal extinction, and therefore have significant implications for

the causes of Australian late Pleistocene extinctions (Johnson, 2005; Trueman

et al., 2005). However, existing extinction hypotheses are based primarily on

temporal presence or absence patterns of megafaunal taxa and/or humans.

Data relating to megafaunal community population dynamics from integrated

stratigraphic successions from many of those late Pleistocene deposits are

absent or remain undocumented. Therefore, it is not possible to analyse the

response of specific local populations to human arrival and/or climate change.

Thus, the operational details of existing megafauna extinction hypotheses are

difficult to test.

The Darling Downs, southeastern Queensland, Australia, is emerging as an

area of major significance in the understanding of late Pleistocene megafauna

extinction. It is an extremely fossiliferous region that contains some of the

youngest megafauna deposits in Australia (Roberts et al., 2001). Previous OSL

and radiocarbon dates of Darling Downs megafauna deposits suggest burial

ages of 51-42 ka (Roberts et al., 2001; Price and Sobbe, 2005). Most Darling

Downs deposits are fluviatile in origin, occurring predominantly in exposed creek

channels within floodplains (Fig. 1), and contain mostly non-articulated remains.

Recent detailed investigations of stratigraphic, sedimentologic and taphonomic

aspects of several different fossil deposits in the Kings Creek catchment have

194

Fig. 1. Modern Kings Creek Catchment with heights (in metres) of surrounding peaks, the main

deposit (site QML796) and other deposits mentioned in the text (QML). GDR: Great Dividing

Range; KCC: Kings Creek Catchment; QML: Queensland Museum Locality.

established the formational processes and provenance of fossil material in

some of those sites (Molnar et al., 1999; Price, 2005; Price and Sobbe, 2005;

Price and Webb, in press). Although most deposits are dominated by small,

unidentifiable shards of bone, the small palaeocatchment size precludes long

distance transport (Price, 2005). Taphonomic analysis of identifiable material

suggested minimal reworking and that most identifiable bones were derived

from the proximal floodplain near the time of deposition (Price and Sobbe, 2005;

Price and Webb, in press). Several of the deposits also contain articulated and

associated remains of megafaunal species (Molnar et al., 1999; Price and

Webb, 2005, in press).

Previous palaeoecological analysis of site QML1396 in Kings Creek (Fig. 1)

suggested that habitats had changed along with a loss in faunal diversity

between deposition of the two fossiliferous horizons (Price and Sobbe, 2005).

However, accumulation bias could not be confidently ruled out as the cause of

diversity loss at the site. Subsequently, the sedimentology and taphonomy of

195

nearby site QML796, which contains three sequential fossiliferous horizons,

were documented, and in that case, decreasing diversity was shown not to

reflect sample or taphonomic bias (Price and Webb, in press). Additionally, the

temporal decline in diversity included the loss of some, but not all megafauna

taxa, over an extended time interval of deposition. The purpose of this paper is

to: 1) investigate more specifically, the population dynamics of the megafaunal

assemblages at QML796 so as to test the results from site QML1396; 2)

document a detailed palaeoecological record of the region throughout the late

Pleistocene; and 3) aid establishment of a detailed chronology of deposition by

introducing different dating methods.

2. Darling Downs deposits

The Pleistocene Kings Creek catchment represented a series of permanent

and ephemeral streams within a geographically small catchment (Price, 2005;

Price and Webb, in press). Site QML796 is located in the northern bank of

Kings Creek (Figs. 1 and 2) and its sedimentology and taphonomic

characteristics were described in detail by Price and Webb (in press). The

deposit contains both high-velocity lateral accretion deposits and low velocity

vertical accretion deposits. Three highly fossiliferous horizons (A7, A4 and A1

horizons; Fig. 2) form the focus of the present investigation. The basal

fossiliferous unit, ‘A7 horizon’, represents lag and bar deposit in a main channel.

Upwardly, the unit passes into clay-silt-rich overbank deposits. The middle ‘A4

horizon’ represents minor stacked channel elements with deposition occurring in

small tributaries on the interfluve during high rainfall periods. The ‘A1 horizon’ is

the uppermost unit, and its geometry indicates crevasse channel and splay

deposition on the floodplain adjacent to the channel belt (Price and Webb, in

press). Deposition of low velocity, vertically accreted sediments occurred

between each of the main fossiliferous units. Taphonomic data suggest that

each main fossiliferous unit had the potential to sample similarly sized taxa. The

preservation of fossil material in the major horizons ranges from abraded, highly

mineralised, unidentifiable bone ‘pebbles’, to complete, pristinely preserved

196

Fig. 2. Measured stratigraphic column of sites QML796 and QML1396 with dates (ka) obtained

from AMS 14C and U/Th methods.

skeletal elements. Collectively, the taphonomic data suggest that most of the

identifiable material was accumulated and transported into the deposit from the

surrounding proximal floodplain. Faunal lists compiled for analysis in this paper

use only those taxa that are represented by unabraded material, and hence, are

unlikely to have been significantly transported or reworked.

Most other deposits in the catchment occur upstream from site QML796 (Fig.

1). Site QML1396 is located in the southern bank of Kings Creek (Fig. 1; Price

and Sobbe, 2005). The basal fossiliferous unit (Horizon B) is litho- and

biostratigraphically correlated to the A7 horizon of QML796 (Fig. 2; Price &

Webb, in press). The deposit passes upwards into overbank (crevasse splay)

deposits. Due to differential modes of accumulation within QML1396 and

interpreted sampling bias of the Pleistocene channel, comparisons between

faunal assemblages of the different horizons are limited (Price and Sobbe,

2005). Stratigraphic successions for most other deposits in the Kings Creek

catchment are poorly known (e.g., sites QML100, QML783; QML872, and

QML913; Fig. 1).

197

3. Methods

3.1. Sampling procedure

Fossils were collected both by in-situ and by bulk removal of sediment for

sieving to target small-sized specimens. Sediment was washed through graded

sieves ranging from 10mm to 1mm, and small bones were sorted following

techniques described in Andrews (1990). Additional details regarding the

excavation of the deposit are given in Price and Webb (in press). Identification

of the fossil material was made by comparative morphological and

morphometrical techniques. Species MNI (minimum number of individuals) for

each main fossiliferous unit was determined by Price and Webb (in press). Taxa

represented by abraded material were excluded from subsequent

palaeoecological analyses, as that material has a higher likelihood of being

reworked from older deposits.

Higher systematics follow Beesley et al. (1988) for molluscs, Glasby et al.

(1993) for amphibians and reptiles, and Aplin and Archer (1987) for mammals.

Body weight estimates of taxa were taken from Strahan (1995) and Cogger

(2000) for extant taxa; and Hecht (1975), Murray (1991), Wroe (2002) and Wroe

et al., (2003a, b) for extinct megafauna.

3.2. Ecological analogies to modern habitats

Andrews et al. (1979) demonstrated that the community structure of mammal

communities from similar habitat types is consistent, even where a comparison

of taxa between habitat types indicates few or no species in common. Andrews

et al. (1979) suggested that habitats of mammalian communities can be

predicted on the basis of their ecological diversity. Hence, establishing the

community structure of modern mammal faunas from particular habitats and

subsequent comparison to the community structure of fossil mammal

assemblages has predictive value for assessing palaeohabitats (Andrews et al.,

1979). Certain aspects of community structure of modern Australian mammalian

faunas were compared to the interpreted community structure of fossil

198

mammals from each of the three main fossiliferous horizons of QML796. The

methodology utilised is based largely on work by Andrews et al. (1979) for

African faunas. Faunal lists of twelve modern Australian faunas were compiled

and examined for each of three main habitat types- closed woodland/rainforest,

open woodlands/mesic, and low open woodlands/grasslands (Table 1). The

Table 1. Vegetative characteristics of modern habitat types.

Locality Vegetation References (vegetation

and/or fauna)

Uluru, Northern Territory Low mulga scrublands, spinifex

grasslands

Reid et al., 1993

Gibson Desert, Western

Australia

Low open scrubland, hummock

grasslands

MacKenzie and Burbidge,

1979; Friend, 1990

Victoria Desert, Western

Australia

Low open woodlands, hummock

grasses on sand plains


1979; Friend, 1990

Little Sandy Desert, Western

Australia

Low open woodlands, hummock

grasslands, spinifex sandplains


1979; Friend, 1990

Brigalow Belt (Vegetation group

7), Queensland

Dry to open woodland with grass

or heath understorey

McFarland et al., 1999

Darling Downs, Queensland Open grasslands on floodplain,

woodlands with grassy and

shrubby understorey closer to

hillsides

Van Dyck and Longmore,

1991; Fensham and

Fairfax, 1997

Texas, Queensland Savannah woodlands Archer, 1978

Bungle Bungle, Western

Australia

Woodlands, open forest, low

open woodlands, open

scrublands

Woirnarski, 1992

Atherton uplands, Queensland Closed, wet sclerophyll forest Williams et al., 1996

Thornton lowlands,

Queensland

Closed, wet sclerophyll forest Williams et al., 1996

Windsor uplands, Queensland Closed, wet sclerophyll forest Williams et al., 1996

Townsville lowlands,

Queensland

Closed, wet sclerophyll forest Williams et al., 1996

modern localities were selected from a variety of different biogeographic regions

and climatic zones and reflect datasets with sound coverage. Several aspects of

199

community structure, including feeding adaptation, locomotory, and life habit

data, were derived from each of the three main habitat types. Bats were

excluded from the analysis of the modern faunas as they are unrepresented in

the QML796 assemblage (following Andrews et al. 1979). Additionally, there

have been several extinctions of small-sized mammals in Australia since

European settlement, particularly in semi-arid and arid environments. Hence,

modern faunas were selected that include knowledge of species present during

the historic period both at the time of and after European settlement. Feeding

adaptation data from the modern faunas were based on six main feeding types.

The categories are fairly broad and were limited to insectivores, frugivores,

browsers, grazers, carnivores and omnivores. Locomotory data are broadly

constrained to reflect the proportion of semi-aquatic, fossorial, terrestrial

quadruped (including cursorial, subcursorial, mediportal and graviportal taxa),

saltatorial, scansorial and arboreal species within each modern habitat type. Life

habit data are based on a species’ most active portion of a 24 hour period and

reflect the proportions of species representing diurnal-crepuscular, crepuscular-

nocturnal and nocturnal habits.

The ecological aspects of modern mammalian species were derived from

Strahan (1995). Ecological aspects of extant taxa that occur as fossils in the

QML796 assemblage were drawn by analogy to extant populations. Ecologies

of fossil taxa were largely derived from Bartholomai (1973; 1975), Murray (1984)

and Flannery (1990).

The percentage of taxa representing each category of each ecological aspect

was calculated at the site level, and means were calculated for each main

habitat type. Pearson bivariate correlation statistics were calculated to test the

similarity between fossil assemblages and 1) individual modern habitat

localities, and 2) means of modern communities, using the SPSS © statistical

package. Correlations were considered to be significant at the 95% confidence

level.

200

3.3. Diversity estimates

The ability to quantify diversity is an important tool when attempting to

understand community structure (Vermeij and Leighton 2003). There are

several different ways to estimate the diversity of an assemblage or community.

One of the most simple diversity estimates is by comparison of the total number

of species recorded between assemblages. However, such estimates of species

richness do not take into account several major aspects of diversity including

equability or evenness of the relative abundance of species, or heterogeneity of

the fauna (Willig, 2003). Several indices have been developed that attempt to

take into account species abundance and evenness, and may provide important

information about rarity and commonness of particular species within a

community or assemblage (Buzas and Hayek, 2005). Diversity estimates for site

QML796 were based on Simpson, Shannon-Weiner, Pielou, and Whittaker

diversity indices, and MacArthur rank abundance models for terrestrial species

from each of the main fossiliferous horizons.

The Simpson’s heterogeneity index (D) is calculated by the formula:

( )( )

1

11

=

��

��

�

−−

=�

i

NNnn

D

s

ii (1)

where s is the total number of species, ni is the number of individuals i in the

sample, and N is the total number of species in the sample. D ranges between 0

and 1, and is larger for samples with less heterogeneity. That relationship is

neither logical nor intuitive, so the relationship is inverted with D being

subtracted from 1 so that lower values reflect less heterogeneity (Rose, 1981).

The Shannon-Weiner heterogeneity index (H') is among the most widely

used indices of diversity and is calculated by the formula:

1

ln'

=

−= �i

ppH

s

ii (2)

201

where s is the total number of species in a sample and p is the frequency of the

ith species. The index is primarily used as a measure of heterogeneity or mixed

diversity, but also reflects evenness.

The evenness component of heterogeneity is measured using several

indices. Among the most simple is Pielou’s evenness index calculated by the

formula:

sH

Jln

'= (3)

The calculation is derived from the result of H' and number of species in the

sample (s).

An additional index of evenness is the Whittaker index (E), which is

calculated using the formula:

( )spps

Eloglog 1 −

= (4)

where s is the number of species, pi is the frequency of the most common

species, and ps is the frequency of the rarest species.

Each diversity index has limitations, but the indices can be highly informative

regarding community structure (Buzas and Hayek, 2005).

Diversity and evenness may also be estimated using hypothetical models of

rank abundance of species within a given community or assemblage. Two main

models of the hypothetical distribution of species within a given community were

developed by MacArthur (1957; 1960). The ‘dependent model’ (as hypothesis I

in MacArthur, 1957) predicts that the relative abundance of any species is

dependent on the relative abundance of all other species within a fauna. Thus,

the relative abundance �

��

mN r of the rth rarest species is calculated by the

formula:

( )1

111

=+−

= �

iinnm

Nr

r

(5)

202

where m is the total number of individuals in a fauna, n is the total number of

species in the fauna, and Nr is the abundance of the rth rarest species. Here, m

is the total MNI and Nr is the MNI of the rth species. If relative abundance is

plotted against the logarithm of the rank abundance, the resulting curve is

nearly linear. MacArthur (1957) demonstrated that certain bird communities

from homogeneously diverse tropical and temperate forests fit the dependent

model hypothesis.

The ‘independent model’ (as hypothesis II of MacArthur, 1957) predicts that

the relative abundance of species r is independent of all other species within a

given fauna. The relative abundance mN r of the rth rarest species is calculated

by the formula:

( ) ( )( )n

rnrnmN r −−+−

=1

(6)

where n is the number of species in the fauna and r is the rank abundance of

species r. Here, rank is based on the abundance rather than rarity such that

1+−= rni . The model predicts that the common species are commoner and

rare species are rarer than that predicted by the ‘dependent model’. Hutchinson

(1961) observed independent model-type distributions of diatoms, arthropods

and plankton species in heterogeneous environments.

3.4. Dating

Samples of bivalves (Velesunio ambiguus), charcoal and bone were

submitted to ANSTO (Australian Nuclear Science and Technology Organisation;

Lawson et al. 2000) for the purpose of accelerator mass spectrometry (AMS) 14C dating. Only complete, conjoined bivalves were submitted for dating, as they

are unlikely to have been reworked from older units. V. ambiguus, like most

Unionoidea, have the ability to burrow (Walker, 1981). Hence, it is possible that

individuals selected for dating could have burrowed into sediment older than

that in which they lived. However, at site QML796, stratigraphic and

sedimentologic sequences are preserved intact and there is no evidence of

203

extensive burrowing of bivalves (Price and Webb, in press). Additionally,

bivalves selected for dating included only those that were lying with their valves

horizontal in the sediment and not in ‘growth’ or ‘burrowing’ positions (i.e.,

valves in vertical positions). Those individuals are presumed to have been

deposited in that position and were unlikely to have burrowed into older

sedimentary horizons.

Selection of bivalve and charcoal samples submitted for dating followed the

criteria of Meltzer and Mead (1985): samples were collected from stratigraphic

horizons containing megafauna and other smaller-sized taxa that are entirely

capped on lower and upper layers by different sediments. Results obtained from

AMS 14C dating of bivalves and charcoal should indicate the approximate time

of deposition.

Bone samples from sites QML796 and QML1396 were submitted to

ACQUIRE (Advanced Centre for Queensland University Isotope Research

Excellence, University of Queensland) for U/Th dating. Bone submitted for

dating using both AMS 14C and U/Th dating methods included near complete

megafauna crania and dentaries, isolated teeth, and complete post-cranial

elements. Specimens selected were well-preserved, relatively complete, and

unabraded. Hence, the selection criteria targeted fossil material that was

particularly well preserved, and highly unlikely to have been transported far or

reworked. U-series dating is based on the premise that U is taken up from the

environment by bone apatites that scavenge U, but exclude Th, during

diagenesis. The age is calculated by determining the amount of 230Th that was

produced by the decay of 238U (via intermediate isotope 234U). Since bones are

open systems for uranium, in most cases the U/Th dates represent the mean

ages of the U-uptake history and thus the minimum ages of deposition

(Simpson and Grün, 1998; Thorne et al., 1999; Zhao et al., 2001). Meltzer and

Mead (1985) considered that direct dating of fossil bone commonly represents a

‘strong’ association between fauna and deposition time and is desirable for

securely dating fossil assemblages.

204

4. Results

4.1. Species

Over 50 taxa were identified at QML796, ranging from molluscs (freshwater

and terrestrial), teleosts, anurans, chelids, squamates, aves, monotremes,

marsupials and placentals (Tables 2-3). The most common groups recovered

were freshwater molluscs, in particular, the thiararid gastropod Thiaria

(Plotiopsis) balonnensis, represented by several thousands of individuals from

each stratigraphic horizon. The most common terrestrial vertebrates recovered

from each horizon were murids, being represented mainly by isolated teeth.

Small-sized taxa (i.e., <1kg) dominate each main fossiliferous horizon (Fig. 3).

Terrestrial taxa weighing in excess of 100 kg were proportionately most

common in A7 and least common in A1 (Fig. 3).

Fig. 3. Body weight distributions of terrestrial vertebrate taxa recorded from site QML796.

Several extant species recorded in the deposit have modern populations that

no longer occur sympatrically. Such associations are regarded as non-analogue

species pairs (Stafford et al., 1999). Price (2005) identified non-analogue

species associations of bandicoots from the A7 horizon (as ‘the main bandicoot

fossiliferous horizon’ in Price, 2005). Additional non-analogue species pairings

also were identified in the other main fossiliferous horizons (Tables 4-6).

Population sizes of several taxa appear to have decreased over the period of

deposition (Figs. 4, 10). For example, within Macropodinae (kangaroos),

population sizes of most species declined over the period of deposition.

Troposodon minor declined from A7 (N = 14, 1.8%) to A4 (N = 10, 0.7%), and

was not sampled in A1. Macropus agilis siva declined from A7 (N = 18, 2.4%) to

205

A4 (N = 18, 1.2%), and was not sampled in A1. Similar trends were observed for

the diprotodontoid, Diprotodon sp., whose populations declined from A7 (N =

26, 3.4%) to A4 (N = 42, 2.9%), and was not sampled in the A1 horizon.

Table 2. Distribution of non-mammalian taxa within each main fossiliferous horizon at QML796,

with their preferred or inferred habitat preferences.

Species A

7

A4

A1

Fres

hwat

er

Rip

aria

n

Vin

e th

icke

ts

Scr

ubla

nd

Clo

sed

woo

dlan

d

Ope

n w

oodl

and

Ope

n/

gras

slan

d

Velesunio ambiguus x x x x

Corbicula (Corbiculina) australis x x x x Thiara (Plotiopsis) balonnensis x x x x

Gyraulus gilberti x x x x Glyptophysa gibbosa x x

Paralaoma caputspinulae x x x x Coencharopa sp. x x x x

Gyrocochlea sp. x x x x Strangesta sp. x x

Austrosuccinea sp. x x x x x

Teleost gen. et. sp. indet. x x x x Limnodynastes tasmaniensis x x x x x x x x

L. sp. cf. L. spenceri x x Kyarranus sp. x x x

Chelid gen. et sp. indet. x x x x Tympanocryptis lineata x x x x

Physignathus leseurii x x x x x ‘Sphenomorphus Group’ sp. 1 x x x x x x x x x

‘Sphenomorphus Group’ sp. 2 x x x x x x x x x

‘Sphenomorphus Group’ sp. 3 x x x x x x x Tiliqua rugosa x x x x x x

Varanus sp. x x x x x x x x x Megalania prisca x x x x x x

Elapid gen. et sp. indet. x x x x x x x x x Anatid sp. A x x

Anatid sp. B x x

Gallinula morterii x x Dromaius novahollandiae x x x x x

206

Table 3. Distribution of mammalian taxa within each main fossiliferous horizon at QML796, with

their preferred or inferred habitat preferences.

Species

A7

A4

A1

Fres

hwat

er

Rip

aria

n

Vin

e th

icke

ts

Scr

ubla

nd

Clo

sed

woo

dlan

d

Ope

n w

oodl

and

Ope

n/

gras

slan

d

Ornithorhyncus anatinus x x x

Tachyglossus sp. x x x x x x

Zaglossus sp. x x x x x x

Sminthopsis sp. x x x x x x x x

Antechinus sp. x x x

Dasyurus viverrinus x x x x x

Sarcophilus laniarius x x x

Perameles sobbei x x x ? ? ? ? ?

P. bougainville x x x

P. nasuta x x x x x x x x

Isoodon obesulus x x x x x

Vombatid indet. x x x x

Phascolonous gigas x x x

Palorchestes azael. x x

Palorchestes sp. x x

Diprotodon sp. x x x x

Zygomaturus trilobus x x

Thylacoleo carnifex x x x

Bettongia sp. x x x

Aepyprymnus rufescens x x

Troposodon minor x x x

Macropus agilis siva x x x

M. titan x x x x x

Protemnodon brehus x x x x x

Pr. roechus x x x x

Pr. anak x x x x x

Pseudomys gracilicaudatus x x

Ps. australis x x x x

Pseudomys sp. A x x x x

Rattus sp. x x x x x x x x

Hydromys chrystogaster x x x x x

207

Generally, A7 contains the highest proportion of taxa that are now extinct

(predominantly megafauna) and lowest proportion of taxa that are extant in the

region (Fig. 5). Conversely, A1 contains the lowest proportion of extinct taxa and

highest proportion of extant taxa.

Demonstrating faunal declines in other megafaunal and non-megafaunal taxa

is difficult owing to low numbers of individuals. However, broadly speaking, A7 is

the only unit that sampled megafaunal taxa, such as Phaslcolonous gigas,

Table 4. Non-analogue species pairings from the A7 horizon at QML796. For example, extant

populations of species 7 (Isoodon obesulus) occur allopatrically with species 3 (Kyarranus sp.)

and species 10 (Pseudomys gracilicaudatus), but fossil populations of those species occur

sympatrically within A7.

Species no. Species Modern allopatric species pairing

1 Tympanocryptis lineata 3, 4, 6, 8, 10, 11

2 Tiliqua rugosa 3, 4, 6, 10, 11

3 Kyarranus sp. 1, 2, 4, 5, 7, 9, 11

4 Dasyurus vivverinus 1, 2, 3, 5, 6, 9, 10, 11, 12

5 Perameles bougainville 3, 4, 8, 10, 11

6 Perameles nasuta 1, 2, 4, 9

7 Isoodon obesulus 3, 10

8 Vombatus sp. 1, 5, 9, 11

9 Pseudomys australis 3, 4, 6, 8, 10, 11

10 Pseudomys gracilicaudatus 1, 2, 4, 5, 7, 9

11 Rattus sordidus 1, 2, 3, 4, 5, 8, 9

12 Rattus tunneyi 4

Palorchestes sp. (see also Price and Hocknull, 2005), P. azael, and

Zygomaturus trilobus. For small-sized terrestrial groups such as peramelids

(bandicoots), only two species, Perameles sobbei and Pe. nasuta, were

represented in the entire depositional sequence. In contrast, populations of Pe.

bougainville and Isoodon obesulus were represented only in the older units,

albeit in low numbers. Similarly, populations of most murids (rats and mice)

208

Table 5. Non-analogue species pairings of extant species from the A4 horizon at QML796

Species

no.

Species Modern allopatric species

pairing

1 Limnodynastes spenceri 4, 5, 6, 7, 8, 9, 10, 12

2 Tympanocryptis lineata 4, 5, 6, 7, 9, 10, 12

3 Tiliqua rugosa 4, 5, 7, 9, 10, 12

4 Ornithorhyncus anatinus 1, 2, 3, 11

5 Dasyurus vivverinus 1, 2, 3, 7, 10, 11, 12, 13

6 Antechinus sp. 1, 2, 11, 12

7 Perameles nasuta 1, 2, 3, 5, 11

8 Isoodon obesulus 1, 10

9 Vombatus sp. 1, 2, 3, 11, 13

10 Aepyprymnus rufescens 1, 2, 4, 12, 12

11 Pseudomys australis 4, 5, 6, 7, 9, 10, 12

12 Rattus sordidus 1, 2, 3, 5, 6, 9, 11

13 Rattus tunneyi 5

fluctuated over the period of deposition, with Pseudomys gracilicaudatus

populations being unrepresented post-deposition of A7. Interestingly, those taxa

represented in the basal fossil unit (A7) that were not also sampled in the

youngest horizon (A1), do not occur on the modern Darling Downs.

Table 6. Non-analogue species pairings of extant species from the A1 horizon at QML796

Species no. Species Modern allopatric species pairing

1 Tympanocryptis lineata 3, 4, 5, 6, 8

2 Tiliqua rugosa 3, 4, 5, 6, 8

3 Gallinula morterii 1, 2, 5, 7, 8, 9

4 Dasyurus vivverinus 1, 2, 5, 7, 8, 9

5 Perameles nasuta 1, 2, 3, 4, 7

6 Vombatus sp. 1, 2, 8

7 Pseudomys australis 3, 4, 5, 8

8 Rattus sordidus 1, 2, 3, 4, 6, 7

9 Rattus tunneyi 3, 4

209

Fig. 4. Proportional relative abundance of selected taxa from site QML796. A. Peramelids

(bandicoots); B. Vombatids (wombats) and diprotodontoids; C. Macropods (kangaroos); D.

Murids (rats and mice).

Several taxa clearly persisted in each stratigraphic unit of the deposit.

Populations of the murid, Ps. australis, exhibit a decline over the period of

deposition, but are still represented in the A1 horizon (A7: N = 18, 2.7%; A4: N =

20, 1.4%; A1: N = 4, 0.6%). Macropus titan and Protemnodon anak appear to

have suffered dramatic population declines, but were sampled in the A1 horizon

(Figs. 4, 10). Other megafaunal taxa such as Megalania were abundantly

represented in each stratigraphic horizon (A7: N = 52, 6.8%; A4: N = 51, 3.5%;

A1: N = 58, 8%; Fig. 10) (Price and Webb, in press).

Fig. 5. Present conservation status of taxa recorded from site QML796.

210

Taxa frequenting freshwater habitats are well represented in each

fossiliferous horizon (Tables 2-3). A7 horizon contains the highest number of

taxa that may occur exclusively in closed and scrubby vine-thicket habitats (e.g.,

Coencharopa sp., Gyrococlea sp., Paralaoma caputspinulae, Kyarranus sp.,

Isoodon obesulus, Perameles bougainville), and open woodlands (e.g.,

Sarcophilus laniarius, Palorchestes spp., Zygomaturus trilobus, Thylacoleo

carnifex, Troposodon minor, Macropus agilis siva, and Pseudomys

gracilicaudatus; Tables 2-3). A1 horizon contains the lowest proportion of taxa

that are restricted to specific habitats (Tables 2-3).

4.2. Ecological dynamics

4.2.1. Feeding adaptations

Feeding adaptation components of modern faunas were graphically (Fig. 6)

and statistically compared to those of fossil horizons and suggests that both A7

(σ = 0.008) and A4 (σ = 0.050) were statistically similar to modern

woodland/mesic type habitats. At site level, A7 was significantly similar to the

woodlands/mesic habitats of Texas (σ = 0.030) and Brigalow Belt (σ = 0.027)

and approached significance with the Bungle Bungle fauna (σ = 0.089). A4 was

significantly correlated to the Texas region (σ = 0.036) and approached

significance with the Bungle Bungle fauna (σ = 0.096). Additionally, A4 also has

statistically significant similarity to the open habitat of the Victoria Desert (σ =

0.041). A7, A4 and modern woodland/mesic habitats are characterised by a

high proportion of grazers, moderate proportions of insectivores, browsers,

carnivores and omnivores, and low proportions of frugivores (Fig. 6).

The A1 horizon fauna was not significantly correlated to the means of the

feeding adaptation categories of any modern habitat type. However at site level,

A1 was significantly correlated to the woodland/mesic habitats of the Texas

region (σ = 0.013) and approached significance to the Bungle Bungle fauna (σ =

0.079). Additionally, A1 was significantly correlated to open habitat of the

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Fig. 6. Proportion of feeding adaptation categories for the means of modern communities and

interpreted for fossil assemblages of site QML796. A. Modern open habitats; B. Modern

woodlands/mesic habitats; C. Modern closed woodlands; D. A7 Horizon; E. A4 Horizon; F. A1

Horizon.

Victoria Desert (σ = 0.036), and approached significance with the Little Sandy

Desert (σ = 0.094). Hence, the A1 faunal assemblage appears to share

components of both modern woodlands/mesic habitats and open habitats (Fig.

6). A1 is similar to modern habitats with very low proportions of frugivores and

browsers, but differs markedly by having comparatively low proportions of

insectivores (Fig. 6). A1 is similar to modern woodlands and mesic habitats with

high proportions of grazers, and moderate, proportions of omnivores (Fig. 6).

Within the fossil assemblages, an obvious trend exists with a proportional

decrease of browsing taxa relative to a steady increase of grazing taxa over the

period of deposit (Fig. 6). Browsing taxa of the A7 horizon are dominated by

large-sized marsupials including diprotodontoids (Palorchestes azael and

Palorchestes spp. ~300 kg, Diprotodon sp. ~2,700 kg, and Zygomaturus trilobus

~500 kg) and macropodines (Troposodon minor ~45 kg). The grazing marsupial

taxa are generally smaller in size and include large and small vombatids

(Phascolonous gigas ~150 kg, and Vombatus sp. ~30 kg), and macropodines

(Macropus agilis siva ~25 kg, M. titan ~85 kg, Protemnodon anak ~50 kg, Pr.

brehus ~75 kg, and Pr. roechus ~85 kg). By the time of deposition of A4, three

of those browsing taxa, Pa. azael, Palorchestes sp. and Z. trilobus, and one

grazing taxon, Ph. gigas, were unrepresented. By the time of deposition of the

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youngest horizon, A1, browsing taxa are completely unrepresented (Fig. 6). A1

Large-sized herbivores are represented solely by grazing taxa, M. titan, Pr. anak

and Pr. brehus. Hence, those data suggest a differential pattern of extinction for

browsing and grazing megafaunal species.

4.2.2. Locomotory adaptations

None of the fossiliferous units significantly correlate to the means of the

locomotory adaptation categories of any modern habitat type. At site level, A7

does not significantly correlate to any single modern habitat. The A4

assemblage approached significance with the mean of the modern

woodland/mesic habitats (σ = 0.080), and A4 correlates to the woodland/mesic

habitats of Texas (σ = 0.018) and approaches significance with Bungle Bungle

(σ = 0.095). A1 significantly correlates to the mesic habitat of the Bungle Bungle

fauna (σ = 0.032).

Fig. 7. Proportion of locomotory adaptation categories for the means of modern communities and

interpreted for fossil assemblages of site QML796. A. Modern open habitats; B. Modern

woodlands/mesic habitats; C. Modern closed woodlands; D. A7 Horizon; E. A4 Horizon; F. A1

Horizon.

Each horizon is similar to modern woodlands in having relatively high

proportions of terrestrial quadruped and saltatorial species (Fig. 7). The A7

assemblage has the highest proportion of terrestrial quadruped species,

including megafauna taxa such as Palorchestes spp., Diprotodon sp.,

Zygomaturus trilobus, Thylacoleo carnifex, and small-sized mammals including

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Perameles bougainville, P. sobbei, P. nasuta, and Isoodon obesulus.

Additionally, each horizon shows similarities to modern open habitats in having

low proportions of scansorial and arboreal species (Fig. 7). However, they differ

markedly from such habitats in having a lower representation of fossorial taxa.

High proportions of fossorial taxa are characteristic of modern open habitats

(Fig. 7). However, a marked trend in the increase of fossorial taxa over the

period of deposition is evident (Fig. 7).

4.2.3. Life habits

Life habit adaptation components of modern faunas were graphically (Fig. 8)

and statistically compared to those of fossil horizons and suggest that both A7

(σ = 0.047) and A4 (σ = 0.007) were statistically similar to modern

woodland/mesic type habitats. At site level, A7 approached significance to the

open habitat of the Victoria Desert (σ = 0.091), and woodland/mesic habitats of

the Brigalow Belt (σ = 0.091). A4 does not correlate significantly to any single

Fig. 8. Proportion of life habit categories for the means of modern communities and interpreted

for fossil assemblages of site QML796. A. Modern open habitats; B. Modern woodland/mesic

habitats; C. Modern closed woodlands; D. A7 Horizon; E. A4 Horizon; F. A1 Horizon.

modern habitat analysed. A1 correlates to the open habitat of the Victoria

Desert (σ = <0.001), and woodland/mesic habitats of the Brigalow Belt (σ =

<0.001) and Bungle Bungle (σ = 0.028). Additionally, A1 approaches

significance to the mesic habitats of the modern Darling Downs (σ = 0.058) and

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closed habitat of the Townsville lowlands (σ = 0.087). Modern closed and open

habitats are very similar to each other in having high proportions of nocturnal

taxa, moderately low proportions of crepuscular taxa, and low proportions of

diurnal species (Fig. 8). Generally, the fossil assemblages most closely

resemble modern woodland/mesic habitats in having more similar proportions of

crepuscular and nocturnal species (Fig. 8). The greater proportion of diurnal

species in the A7 horizon reflects a higher proportion of megaherbivores in

comparison to the other horizons.

4.3. Diversity

In raw data the A4 horizon is the most taxon-rich fossiliferous unit, but it

contains the most samples. Price and Webb (in press) used rarefaction analysis

to account for bias related to sample size and demonstrated that A7 is the most

diverse horizon, followed by A4 and A1. Those results are supported here by

Simpson and Shannon-Weiner diversity estimates that indicate that the diversity

of terrestrial taxa decreased dramatically between the time of deposition of A7

and A1 (Fig. 9A-B). Similarly, Pielou and Whittaker indices indicate decreasing

evenness over the same time period (Fig. 9C-D).

Calculations of MacArthur’s dependent and independent models were based

on the number of terrestrial taxa recorded from each horizon (A7: N = 49; A4: N

= 53 taxa; A1: N = 38 taxa). Observed abundances of taxa within each horizon

Table 7. Standard deviations for MacArthur rank abundance models.

Horizon Dependent Independent

A7 0.0608 0.0532

A4 0.0751 0.0676

A1 0.0924 0.0834

were ranked in decreasing abundance and compared to results of the models.

The distribution observed in the fossil assemblages indicate that common taxa

tend to be commoner and rarer taxa tend to be rarer than that predicted by the

dependent model. Thus, the distribution and standard deviations of terrestrial

215

species from each main fossiliferous horizon fit the independent model more

closely than the dependent model (Fig. 10, Table 7).

Fig. 9. Diversity indices of terrestrial taxa from site QML796. A. Simpson’s heterogeneity index;

B. Shannon-Weiner heterogeneity index; C. Pielou’s evenness index; D. Whittaker evenness

index.

4.4. Dating the deposits

Dating results confirm that both QML796 and QML1396 are late Pleistocene

(Table 8). However, the dating results from different materials and methods are

not in agreement with each other and in some cases, are not internally

consistent (Table 8). Generally, AMS dates indicate that deposition occurred in

the late Pleistocene, just prior to the last glacial maximum (Table 8). However,

AMS 14C results for fossil bivalves (Velesunio ambiguus) returned ages that are

problematic. No bivalves from the A7 horizon at site QML796 were submitted for

dating. However, Horizon B of site QML1396 is litho- and biostratigraphically

correlated to the lower portion of A7 and was dated to 44.3 ± 2.2 ka (Price and

Sobbe, 2005). Stratigraphically younger horizons at QML796 returned dates that

fluctuated widely from 33-24 ka within the upper coarse unit of the A4 horizon.

The coarse-grained horizon between A4 and A1 contained associated

216

Fig. 10. MacArthur predicted dependent, independent and actual ranked relative abundance data

of terrestrial taxa from site QML796. A. A7 Horizon; B. A4 Horizon; C. A1 Horizon.

217

Protemnodon sp. remains, and bivalve dates varied between 32-25 ka. Dates

ranged from 33-24 ka in the A1 horizon. Hence, AMS 14C dates from bivalves

provide no resolution for the A4 to A1 sequence and some individual samples

returned dates that are out of stratigraphic order.

Table 8. AMS 14C and U/Th dating results for Darling Downs deposits.

Sample

code

Method Site Material Horizon Age 2 �

error

OZF892 AMS 14C QML796 bivalve A1 28 430 420



OZG539 AMS 14C QML796 bivalve A1 24 300 340


OZF895 AMS 14C QML796 macropod vertebra A1 - -

SS020 AMS 14C QML796 Megalania tooth A1 - -

OZG545 AMS 14C QML796 Protemnodon molar A1 - -

OZG852 AMS 14C QML796 charcoal A1 36 000 1 200

SS051 U/Th QML796 Protemnodon brehus skull A1 55 020 310

OZG541 AMS 14C QML796 bivalve btn A1&A4 25 490 480

OZG542 AMS 14C QML796 bivalve btn A1&A4 32 540 560

OZG853 AMS 14C QML796 charcoal btn A1&A4 40 000 1 500

OZG543 AMS 14C QML796 bivalve A4 33 870 1 260


OZF899 AMS 14C QML796 macropod rib A4 - -

SS021 AMS 14C QML796 Macropus titan iscisor A4 - -

OZG546 AMS 14C QML796 Protemnodon molar A4 - -

OZG854 AMS 14C QML796 charcoal A4 38 350 1 200

SS056 U/Th QML796 Protemnodon anak skull A4 80 235 399

SS052 U/Th QML796 Protemnodon dentary A7 78 757 514

OZG855 AMS 14C QML1396 charcoal Horizon D 45 150 2 400

OZG548 AMS 14C QML1396 bivalve Horizon B 44 300 2 200

OZG547 AMS 14C QML1396 bivalve Horizon B >49 900 -

SB021 U/Th QML1396 Protemnodon dentary Horizon B 88 350 699

AMS 14C dating of charcoal appears to be more reliable and returned ages in

correct stratigraphic sequence (Table 8). At site QML1396, an overbank unit

218

that overlies the channel deposit was dated to 45.15 ± 2.4 (Price and Sobbe,

2005) and may be similar in age to, or younger than the A7 overbank unit at

QML796. Charcoal recovered from the upper coarse unit of the A4 horizon (site

QML796) was AMS 14C dated to 38.35 ± 1.2 ka. The small coarse fill unit

between A4 and A1 was dated to 40 ± 1.5 ka. Charcoal associated with

megafauna material from the A1 horizon was AMS 14C dated to 36 ± 1.2 ka.

Extraction of collagen from fossil bone and teeth was attempted for dating by

AMS 14C methods, but yield was poor, and the resultant compounds were very

degraded and unlikely to be collagen. Hence, the samples were not suitable for

dating.

Fossil bone dated using U/Th techniques, which provide minimum ages

rather than true ages, returned ages that are significantly older than the AMS 14C dates (Table 8). The dates were not in strict stratigraphic order, but that

could be due to different uranium uptake histories of individual samples.

Megafauna fossil material from the A7 horizon has a U/Th minimum age of

78.75 ± 0.514 ka. U/Th dates obtained for the equivalent stratigraphic unit at

QML1396 return a minimum age of 88.35 ± 0.699 ka. Megafauna material from

the A4 horizon had a minimum U/Th age 80.23 ± 0.399 ka, and from the A1

horizon, a minimum U/Th age of 55.02 ± 0.310 years. Implications of the dates

obtained are discussed below.

5. Discussion

5.1. Palaeoecology

The habitat preferences of taxa in each main fossiliferous horizon of QML796

indicate that a mosaic of habitats was sampled by the creek during the late

Pleistocene. Those habitats included riparian vegetation, vine thickets and

scrubland, open and closed woodlands, and open grasslands (Fig. 11).

MacArthur ranked abundance data of terrestrial taxa support the interpretation

of heterogeneous habitat types (Table 7; Fig. 10).

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Although the presence in each horizon of several species that have modern

allopatric distributions provide conflicting information regarding palaeohabitat

interpretation, they do provide additional support for a mosaic of habitat types in

the Pleistocene catchment. Non-analogue associations of species are generally

time restricted, being common during the late Pleistocene and rare in the

Holocene (Stafford et al., 1999). Such habitat diversity or patchiness is

commonly hypothesised to have been maintained by more equable climates

with lower seasonality (Lundelius, 1983; 1989). More equable climates may be

achieved via lower temperature and evaporation rates resulting in more

available moisture throughout the year. Such a climatic regime may have

operated on the Darling Downs at times during the late Pleistocene (Price,

2005; Price et al., 2005).

Several other deposits in the Kings Creek catchment contain similar faunas

to those recorded from QML796 (Table 9). The basal fossiliferous unit at site

QML1396 (Horizon B), 200 metres upstream from QML796 (Fig. 1), is

biostratigraphically correlated to the A7 horizon of QML796 (Fig. 2; Price and

Webb, in press). The palaeohabitat at QML1396 is interpreted to have

consisted of a mosaic of habitat types, similar to those of the A7 and A4

horizons at QML796 (Price et al., 2005; Price and Sobbe, 2005). Site QML783

(Fig. 1) is located in a tributary that flows into Kings Creek, and was dated to 47

± 4 ka years using OSL techniques (Roberts et al., 2001). The assemblage is

dominated by large-sized taxa, but Molnar et al. (1999) suggested that that may

reflect sampling bias in the Pleistocene channel system during deposition rather

than subsequent collecting bias. Typical Darling Downs megafauna are

represented in the deposit (Table 9) and indicate the presence of woodlands

and open grasslands during the period of deposition. The large-sized taxa

include Sarcophilus sp., Phascolonous gigas, Thylacoleo carnifex, Diprotodon

sp., Macropus titan and Protemnodon roechus, an assemblage that is generally

characteristic of the A7 horizon of site QML796.

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Table 9. Terrestrial faunal lists for specific Pleistocene Kings Creek catchment deposits. For

location of deposits, see figure 1.

Species QML100 QML783 QML872 QML913 QML1396

Horizon B

QML1396

Horizon D

Coencharopa sp. x

Gyrococlea sp. x

Austrosuccinea sp. x

Xanthomelon pachystylem x

Strangesta sp. x

Saladelos sp. x

Limnodynastes tasmaniensis x

L.sp. cf. L. dumerili x

Neobatrachus sudelli x

Kyarranus spp. x

Tympanocryptis lineata x x x

“Sphenomorphus Group” x x

Tiliqua rugosa x

Cyclodomorphus sp. x

Megalania prisca x x

Varanus sp. x

Elapid x

Zaglossus sp. x

Sminthopsis sp. x

Dasyurus sp. x x

Sarcophilus sp. x x x

Thylacinus cynocephalus x

Perameles bougainville x

Pe. nasuta x

Phascolomys medius x

Vombatus sp. x x

Phascolonous gigas x x x

Palorchestes sp. x x

Zygomaturus sp. x

Diprotodon sp. x x x x x

Thylacoleo carnifex x x x x

Aepyprymnus sp. x

Sthenurus sp. x x

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Table 9 continued

Propcoptodon sp. x x x x

Troposodon minor x x x x

Macropus agilis siva x x x x

Ma. titan x x x x x x

Ma. ferragus x

Ma. altus x x

Ma. pearsoni x

Protemnodon anak x x x x x

Pr. brehus x x x x

Pr. roechus x x x

Onychogalea sp. x

Thylogale sp. x

Pseudomys sp. x x

Rattus sp. x x

murid indet x x x

Several other deposits in the catchment, both upstream and downstream

from QML796, contain Pleistocene faunal assemblages (Table 9). However,

stratigraphic relationships of those deposits to site QML796 remain unclear.

Sites QML100, QML872, and QML913 (Fig. 1) all contain faunal elements

whose ecologies broadly suggest open grassland and woodland habitat types.

However, such palaeoenvironmental interpretations are limited because none of

those deposits have been systematically and thoroughly sampled, and smaller-

sized taxa are poorly known owing to the lack of detailed excavations.

Stratigraphic provenance of taxa from those deposits are also poorly known,

hence, the collections may represent time-averaged assemblages. However,

despite such reservations about palaeoenvironmental interpretation, it is clear

that each deposit contains extinct taxa that are characteristic of either the A7 or

A4 horizons of QML796 (e.g., Zaglossus sp., Phascolonous gigas, Palorchestes

sp., Zygomaturus sp., Diprotodon sp., Thylacoleo carnifex, Troposodon minor,

and Protemnodon roechus; Table 9).

222

5.2. Habitat change

Johnson and Prideaux (2004) suggested that Pleistocene megafauna

extinction was not related to climate change or to increased burning (natural or

anthropogenic), because they did not observe differential extinction patterns for

browsers and grazers that might reflect such changes in habitat. Hence, they

preferred an overhunting model for megafauna extinction. However, differential

patterns of extinction for grazers and browsers were observed in the

stratigraphically well-documented QML796 succession (Fig. 6). The differences

in local extinction patterns of Darling Downs browsing and grazing megafauna

could be explained by: 1) taphonomic sampling bias in the Pleistocene

catchment relating to species size; 2) human overhunting of larger-sized

browsing megafauna; or 3) habitat change in the catchment.

Sedimentologic and taphonomic data indicate that each main fossiliferous

horizon had the potential to sample similarly large-sized taxa (Price and Webb,

in press). For example, A1 sampled very large-sized species such as Megalania

prisca (160-650 kg) in abundance, but several equivalent or smaller-sized

browsing taxa such as diprotodontoids and Troposodon minor, common in older

units, are unrepresented in A1. Thus, if those taxa were also present during the

time of deposition of A1, they would be expected to have been sampled during

deposition (Price and Webb, in press). Additionally, rarefaction analysis

demonstrated that differences in diversity between assemblages were not due

to sampling intensity (Price and Webb, in press). Therefore, the differences are

unlikely to reflect selective sampling bias and hypothesis 1 is not supported.

Hypothesis 2 can also be tested using sedimentologic and taphonomic data.

Such data indicate that: a) most bones in each horizon were broken in a dry or

fossilised state; b) cut markings on bones are solely attributable to activities of

non-hominid carnivores; c) megafauna mortality profiles were not biased toward

the vulnerable age classes (i.e., young or senile); and d) accumulation occurred

via natural fluvial processes, rather than via anthropogenic pathways (Price and

Webb, in press). Additionally, there is no record of humans on the Darling

Downs prior to 12 ka (Gill, 1978), and human remains and stone tools are rare

223

in any case and might not be expected to occur in a non-human habitation

accumulation. Collectively, those data do not support a role for human hunting

of Darling Downs megafauna in the late Pleistocene catchment. Therefore,

there is no support for hypothesis 2, although it cannot be rejected.

Fig. 11. Schematic habitat reconstructions of the Pleistocene Kings Creek Catchment. See figure

10 for key to silhouetted megafaunal figures.

The difference between extinction rates of Darling Downs browsers and

grazers is consistent with hypothesis 3, habitat change in the late Pleistocene

catchment. Although each stratigraphic horizon possesses faunal components

of several habitats (i.e., riparian vegetation, vine thickets and scrubland, open

and closed woodlands, and open grasslands), the proportion of habitat types

differed through time (Fig. 11).The ecosystem dynamics of the A7 and A4

horizons were generally very similar to that of modern woodland/mesic habitat

types. However, the habitats appear to have changed through the period of

deposition, so that by the time of deposition of the A1 horizon, the creek

sampled a more open type environment (Fig. 11). It is generally assumed that

browsing taxa are dependent on structurally complex woodlands, while grazers

are associated with more open, grassy habitats (Johnson and Prideaux, 2004).

Hence, the loss of browsing taxa and proportional increase and persistence of

grazing taxa over the time period of deposition probably was related to the

contraction of woodlands and expansion of grasslands. Similarly, a steady

increase in the proportion of fossorial taxa over the time of deposition indicates

an opening up of the environment.

224

Habitat preferences of non-megafaunal taxa that occur within each main

fossiliferous horizon provide additional support for the contraction of closed,

scrubby vine thickets and woodlands as grasslands expanded. Moreover, the

loss of taxa frequenting woodland habitats was not specifically related to large-

bodied species. Several small-sized taxa such as land snails (Paralaoma

caputspinulae), frogs (Kyarranus sp.), bandicoots (Perameles bougainville and I.

obesulus) and murids (Pseudomys gracilicaudatus) that also had specific habitat

requirements for closed, scrubby vine thickets or woodlands, were not

represented in A1, the youngest horizon. The A1 assemblage of small-sized

taxa is largely dominated by species that have specific preferences for open

habitats (Tympanocryptis lineata and Ps. australis) or are taxa with broad

habitat preferences that also occurred in most other fossiliferous horizons

(Austrosuccinea sp., Limnodynastes tasmaniensis, Sphenomorphus Group sp. 1

and 2, Varanus sp. Sminthopsis sp. Perameles nasuta and Rattus sp.). Many of

those small-sized taxa are rare in the assemblages so it may be a case that

they were simply not sampled equally in each unit (e.g., Signor Lipps effect;

Signor and Lipps, 1982). However, it is unlikely that uncommon taxa with broad

habitat tolerances were sampled more readily than were equally uncommon

taxa that had more specific habitat tolerances, and in selected horizons only.

Therefore, the differences in temporal representation of small-sized taxa with

broad versus specific habitat tolerances is more likely related to habitat change,

rather than to sampling bias against rare taxa.

Price and Webb (in press) observed minimally, a two-stage (i.e., gradual)

extinction of Darling Downs megafauna. Their data are not consistent with an

anthopogenically-driven, sudden ‘blitzkrieg’ extinction event, but are consistent

with a climate-forced model of habitat change (Price and Webb, in press), and

the present analysis supports that hypothesis. Thus far, there is no evidence to

suggest that late Pleistocene habitat changes were related to anthropogenic

firing of the landscape. The paucity of charcoal in the sedimentary record

suggests that burning, either anthropogenically or naturally induced, was

insignificant in the late Pleistocene Kings Creek catchment. Other

225

sedimentologic and taphonomic data (e.g., abundant calcrete formation in an

ephemeral fluvial setting, and possible drought-like megafauna mortality

patterns; Price and Webb, in press) from sites QML796 and QML1396 suggest

a seasonally arid climate during the late Pleistocene, therefore, supporting a

role for aridity in driving late Pleistocene Darling Downs habitat change and

geographic range changes (i.e., local extinctions) of taxa.

A comparison of the interpreted late Pleistocene floristics to the modern

floristics of the Kings Creek catchment is limited owing to the extensive amount

of pastoral activity that has occurred since European settlement (Price and

Sobbe, 2005). However, a review of vegetative surveys from the initial period of

settlement indicates that the pre-European catchment was dominated by

grasslands on the floodplain, with grassy or scrubby woodlands confined to the

slopes closer to the Great Dividing Range (Fensham and Fairfax, 1997). Late

Pleistocene scrubland and woodland contraction and grassland expansion in

the catchment may have been a process that continued until the time before

European settlement. Palaeohydrological data from nearby Fraser Island on the

southeastern Queensland coast suggests increasing aridity leading up to a

particularly severe arid interval during the last glacial maximum, and a following

dry interval through the Holocene (Longmore and Heijnis, 1999). Inferred habitat

changes at QML796 were clearly detrimental to the persistence of several

groups and resulted in major decreases in taxonomic diversity and evenness

over time. Generally, the majority of species that are represented both on the

modern Darling Downs and as fossils in the Pleistocene deposits are those

species that have the broadest habitat tolerances. However, very few of the

modern Darling Downs species have a Pleistocene record from the region

(Table 10), suggesting that major faunal turnover occurred between the

deposition of the A1 horizon and the present. The precise timescale of that

faunal turnover remains unclear and appropriately-aged deposits have not been

documented in the catchment.

226

Table 10. Modern Darling Downs mammal species list, excluding recently introduced species. *

indicates a Pleistocene record from QML796; ** indicates genus only or different species

recorded from QML796.

Species

Tachyglossus aculeatus **

Dasyurus maculatus**

Antechinus flavipes **

A. stuartii **

Phascogale tapoatafa

Planigale maculata

P. tenuirostris

Sminthopsis macoura **

S. murina **

Isoodon macrourus **

Perameles nasuta *

Phascolartos cinereus

Petaurus norfolcencis

Petoroides volans

Pe. peregrinus

Trichosurus caninus

Tr. vulpecula

Acrobates pygmaeus

Aepyprymnus rufescens *

Macropus dorsalis **

M. giganteus **

M. parryi **

M. robustus **

M. rufogriesus **

Wallabia bicolor **

Hydromys chrystogaster *

Melomys cervinipes

Notomys mordax

Rattus fuscipes **

R. tunneyi **

227

5.3. Dating and implications

Dating the Darling Downs fossil deposits has proven extremely problematic,

and dates obtained from different materials and methods are difficult to

correlate. However, site QML796 is ideal for evaluating specific suites of dates

because all materials were recovered in sequential stratigraphic order. Hence,

unlike dated collections from isolated sites, the relative ages of dated samples

from QML796 are well constrained. Initial selection of materials for dating

followed criteria intended to reduce the potential for taphonomic bias such as

reworking and stratigraphic leak. Bivalve, charcoal and bone samples used for

dating were unlikely to have been reworked or transported, and individual

bivalves were unlikely to have burrowed into older sedimentary units.

Regardless of the constraints, AMS 14C dates obtained from fossil bivalves

are not invariably in correct stratigraphic sequence within a horizon. Shells in

open systems may be exposed to contamination when carbon is exchanged

with bicarbonate ions in percolating water, resulting in diagenesis and possible

recrystallisation. However, petrographic examination of the fossil bivalves

submitted for dating by AMS methods does not indicate significant

recrystallisation or fungal borings consistent with a major mass balance change

in C content. The microstructure of the fossil bivalves is almost indistinguishable

from that of modern bivalves from the same catchment.

AMS 14C dating results for charcoal samples returned ages in correct

stratigraphic sequence. However, the ages obtained are close to the

chronological limits of the dating technique. As the likelihood of chemical

exchanges with contamination by younger carbon increases with sample age,

the effect of a trace of modern contamination becomes acute as the dating limit

is approached and the quantity of residual 14C is small. Generally, such effects

may make dating less reliable for samples older than 30 000 years (O’Connell

and Allen, 2004).

U/Th dates obtained for fossil material from the Kings Creek deposits are

also problematic. Some dates occur out of stratigraphic order (which is not

unexpected as U/Th dates for fossil bone are only minimum ages), but more

228

importantly, they are approximately 20 000-40 000 years older than dates

obtained on materials using AMS 14C methods. Dates obtained from the

apparently equivalent stratigraphic horizon at two different localities (QML796

and QML1396) differ by ~10 000 years.

Reasons for the discrepancy in ages between samples from the same

stratigraphic horizon (i.e., out of order) and for differences between the two

dating methods invite speculation. The interpretation of U/Th dates for fossil

bones is subject to uranium uptake histories/modes (Pike et al., 2002), which

can be significantly different in different types of fossil materials, e.g., tooth

dentine versus enamel (Zhao et al., 2001). Uranium can also experience

significant mobilisation and leaching (leading to U/Th age overestimation) in

open systems, which may be enhanced in carbonate-rich sedimentary deposits

(Bowler et al., 2003) such as those considered here. All such processes affect

interpretation of U/Th dates. Thus, a combination of U-remobilisation with

variations in the U-uptake histories may explain differences in dates obtained for

different stratigraphic horizons at QML796 and the equivalent stratigraphic

horizon of QML796 and QML1396. Nevertheless, in most circumstances U-

uptake is the dominant process, outweighing U-leaching, simply because bone

apatite is an effective U scavenger (Grün et al., 2000; Pike et al., 2002).

Regardless, in terms of the fossils in this study, it is unknown whether U-

leaching (leading to U/Th age overestimation) occurred. That problem can be

clarified with ICP-MS U concentration profiling across the bones (Pike et al.,

2002) and that study is currently underway.

Regardless of the dating irregularities, the assemblages clearly were

deposited during the late Pleistocene. Whichever dating technique is correct,

deposition of site QML796 occurred over a period of approximately 9 000 - 33

000 years. Importantly, that interpretation does not depend on which technique

is most correct, but on the internal consistency within each technique because

the relative ages of the horizons are firmly established by superposition. Clearly,

significant habitat change and localised species extinctions occurred within the

catchment over that interval of time at QML796. However, in the absence of

229

more reliable dates, it is difficult to determine: 1) the precise temporal scale over

which the habitat change and species extinction occurred; 2) the timing of such

events in relation to the continent-wide extinction of the Australian Pleistocene

megafauna; and 3) the timing of faunal turnover in relation to the human

colonisation of the Sahul (Australia and New Guinea) continent. Regardless of

the problems relating to the dating of Kings Creek fossil deposits, the

interpretations have several important implications for the extinction of the

Darling Downs megafauna.

If those greater ages based on the U/Th dates are accepted, habitat change

and megafaunal extinction occurred on the Darling Downs before 88-55 ka and

any anthropogenic component relating to the extinction may be effectively ruled

out. There is no evidence of human occupancy prior to 12 ka on the Darling

Downs (Gill, 1978), and at most, the age of the A1 horizon may overlap with

initial human colonisation of the Sahul continent. However, data from the A7

and A4 horizons (> 80 ka) indicate that severe habitat change with associated

decreasing faunal diversity, was already well underway, and may pre-date the

arrival of humans in Australia. Ice core and deep sea drilling data from

Antarctica and the southwest Pacific respectively suggest cooler temperatures

between 85-65 ka (Petit et al., 1999; Pahnka et al., 2003). However, warmer

and wetter conditions were present from 65-45 ka (Turney et al., 2001a; Bowler

et al., 2003). That initial cooling may be of geographic significance in the

Southern Hemisphere (Petit et al., 1999) and thus, provide additional support for

the role of climate in driving Pleistocene Darling Downs habitat changes and

species extinctions. Based on the U/Th dates, if early humans did have an

impact on the persistence of Darling Downs megafauna, they were impacting on

an extinction event that was already well underway.

If the AMS 14C dating results of charcoal are more accurate, then

chronologies based on QML796 and QML1396 suggest that deposition took

place from approximately 45-36 ka. Again, there are several important

implications regarding such a hypothesis. Firstly, it implies that some

megafaunal species (Megalania prisca, Macropus titan, Protemnodon anak and

230

P. brehus) survived until at least 36 ± 1.2 ka on the Darling Downs, supporting

recent suggestions that Australian megafauna extinctions occurred after ~ 46.4

ka (e.g., Trueman et al., 2005). Secondly, localised extinction of Darling Downs

megafauna occurred gradually over the period of deposition- there is roughly a

30% stepwise decrease in the number of extinct taxa represented within each

horizon over time (A7: N = 15 taxa; A4: N = 11 taxa; A1: N = 6 taxa). That

suggests that extinction of the megafauna as a whole was not a synchronous

event on the Darling Downs, and therefore, may not have occurred

synchronously across the continent as previously suggested by Roberts et al.

(2001). Thirdly, habitat change and megafauna extinctions took place over a

period of anywhere from ~5 500 to ~12 500 years, potentially overlapping with

the initial human colonisation of the Sahul continent. Proponents of the blitzkrieg

extinction hypothesis suggest that extinction takes place rapidly after human

colonisation (Martin, 1984; Flannery, 1990). Hence, a potentially long duration

between the overlap of Pleistocene megafauna and humans would not support

the ‘blitzkrieg’ extinction hypothesis (Barnosky et al. 2004, Wroe et al., 2004).

Up until 45 ka, the northern monsoon was still operating over much of Australia

(Johnson et al., 1999). However, humidity was decreasing by 40 ka (Turney et

al., 2001a; Bowler et al., 2003), and the continent descended rapidly into a

period of sustained aridity from 40-30 ka resulting in major vegetational changes

in several regions (Kershaw, 1994; Longmore and Heijnis, 1999; Turney et al.

2001b; Field et al., 2002; Bowler et al, 2003). Violent swings in El Niño southern

oscillation from 40 ka (Kershaw et al., 2000) coincided with the intensified aridity

that was sustained from 30 ka to the last glacial maximum (Lambeck and

Chappell, 2001). Such independently derived climatic change chronologies fit

well with late Pleistocene Darling Downs habitat changes and species

extinctions.

However, despite the dating of 25 samples using different methods, an

accurate chronology remains to be established for Darling Downs fossil

deposits. Dating such deposits accurately is critical, and additional dating

techniques must be applied. While it is tempting to favour one suite of dates

231

over the other, considering the disparity between the results of the two methods,

it may yet prove unwise. Clearly, additional dating based on more reliable

materials (e.g., travertines) or more robust assessment of U-uptake leaching

history in the bones is required to test the dates presented here and to

determine the true age of the fauna and chronology of depositional events.

6. Conclusions

A multifaceted palaeoecologic investigation of site QML796, Kings Creek,

Darling Downs, has revealed significant insights into the changing faunas and

habitats of the region during the late Pleistocene. The basal fossiliferous unit

contains a variety of extinct and extant taxa that indicate the presence of a

mosaic of riparian vegetation, vine thickets, scrublands, open and closed

woodlands, and open grassland habitats on the late Pleistocene floodplain. The

geographically small-size of the late Pleistocene catchment precludes the

assemblages being mixtures of material transported from widely distributed

habitats. The woody and scrubby habitats contracted over the period of

deposition, so that by the time of deposition of the youngest horizon, the creek

sampled a more open-type environment. That change potentially continued

through to the time just before European colonisation, when the catchment was

dominated by expansive grasslands, with woodlands confined to hillsides. The

documented habitat changes correlate with the local extinction of several taxa in

the region. The local extinction of megafauna was not body-size specific, as a

variety of large- and small-sized megafaunal taxa were lost over the same

period. Rather, the loss of taxa appears to be selective towards those that

preferred woodlands. Other non-megafaunal taxa that persisted in the youngest

horizon were those that have habitat preferences for open areas, or are

common in a variety of habitats.

AMS 14C and U/Th dating confirm that the Kings Creek deposits are latest

Pleistocene in age, but the dating has proven problematic, and an accurate

chronology is yet to be established. Current dates are equivocal because 14C

dates yielded results that are not in stratigraphic sequence, and 14C and U/Th

232

dates are out of agreement by 20-30 ka or more. Although independent climatic

data better support the charcoal AMS 14C dates to some degree, the older dates

currently cannot be ruled out. Hence, additional efforts to date Darling Downs

sites are critical. Regardless of the dates, however, the data show a strong

correlation of attritional faunal extinction with indicators of climate change from a

single stratigraphic succession. Coupled with sedimentologic data, that

correlation provides support for hypotheses of climate change as the cause for

Darling Downs megafaunal extinction.

Acknowledgments

I thank G. Webb, S. Hocknull, B. Cooke, I. Sobbe, J.-x. Zhao, Y.-x. Feng, B.

Brooke, I. Williamson and A. Cook for helpful discussions on various aspects of

Darling Downs palaeoenvironments. J. Stanisic and A. Baynes assisted in the

identification of molluscs and murids respectively. R. Bell, P. Calquhoun, P.

Hamilton, M. Ng, D. and J. Price, L. Shipton, K.A. Smith, I., D. and A. Sobbe, K.

Spring, T. Sutton, P. Tierney, G. Todd, D. and M. Turner, S. Watt, J. Wilkinson

and countless volunteers provided additional support in the collection and

preparation of fossil material. D. Price prepared figure 11. AMS 14C dating by

ANSTO was supported by AINSE Grants 02/013 and 03/123. U/Th dating by

ACQUIRE was supported by Australian Research Council Linkage Grant

LP0453664. This research was funded in part by both the Queensland

University of Technology and the Queensland Museum.

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GENERAL DISCUSSION

SIGNIFICANCE OF STUDY

This research substantially builds on previous work on Australian, and

particularly Darling Downs, Pleistocene fossil deposits on several different

levels. The Kings Creek catchment provides a unique opportunity to examine

detailed palaeoecological aspects of a Pleistocene floodplain community in a

small geographic sampling area. Fossil accumulations within floodplain

deposits are typically transported, and it is commonly difficult, or in some

cases impossible, to reliably constrain the sampling area of palaeodrainages.

In this study, regional topography was used to constrain the sampling area of

the Pleistocene channel using the size of the modern catchment as an

analogy. The Pleistocene channel was relatively small, hence, fossil material

could not have been transported over distances greater than 25-30 km.

Thus, palaeoecological implications represent a small, well-constrained

geographic area.

Systematic collecting methods utilised during this project were designed to

target the recovery of both large and small-sized taxa. Such methods are

rarely employed in palaeontology owing to their labor intensive nature.

Hence, this project recovered considerable amounts of data that generally

are not available. The methods utilised were particularly important to balance

previous collecting methods that tended to favour large-sized forms and

specimens. The methods led to the recovery of a new species of bandicoot

(Perameles sobbei Price) and several other taxa previously unknown as

fossils on the Darling Downs, including: Glyptophysa gibbosa, Gyraulus

gilberti, Paralaoma caputspinulae, Coencharopa sp., Gyrococlea sp. 1 and 2,

Austrosuccinea sp., Xanthomelon pacystylum, Strangesta sp., Saladelos sp.

(pulmonate molluscs); Limnodynastes tasmaniensis, L. sp. cf. L. dumerili, L.

sp. cf. L. spenceri, ?Limnodynastes sp., Neobatrachus sudelli, Kyarranus sp.

1 & 2 (frogs); Tympanocryptis lineata, “Sphenomorphus Group” 1, 2 and 3,

Tiliqua rugosa, Cyclodomorphus sp. (dragon lizards and skinks);

Tachyglossus sp., Zaglossus sp. (echidnas); Sminthopsis sp., Antechinus sp.

(dasyurids); Isoodon obesulus, Perameles bougainville, Pe. nasuta

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(bandicoots); Bettongia sp. (bettong); Pseudomys gracilicaudatus, Ps.

australis and Hydromys chrystogaster (rodents). The results support Molnar

and Kurz’s (1997) hypothesis that small-sized taxa were more diverse and

widespread during the late Pleistocene than previously considered.

Pleistocene geographic range extensions have also been revealed for

several of those taxa. Additionally, unique, non-analogue assemblages of

species previously unknown to have occurred sympatrically were also

revealed in the Darling Downs fossil record (e.g., bandicoots- Isoodon

obesulus, Perameles bougainville & Pe. nasuta).

The newly documented assemblages have increased the precision of

previous palaeoenvironental interpretations of the region significantly.

Additionally, palaeoecologic analyses followed methodology rarely utilised in

Australian palaeontology. Investigations of specific species ecologies,

coupled with analogies to modern communities and diversity estimates,

allowed for high resolution interpretations of Pleistocene habitats. Several

previously unrecognised habitats were revealed from the assemblages of the

deposits including vine thickets, riparian habitats and closed woodlands.

More precise details of the structure of certain previously recognised habitat

types (e.g., open sclerophyllus woodlands with sparse, scrubby or grassy

understories) were also revealed. Climatic variables could also be inferred

from the analysis of groups such as frogs and bandicoots. For example,

some assemblages of bandicoots from the deposits represent non-analog

assemblages, thereby suggesting more equable seasonality (possibly

maintained by lower temperatures and lower evaporation rates; cf.,

Lundelius, 1983) during the late Pleistocene. That hypothesis is supported

by assemblages of frogs in the deposits. The consistently small body-size of

populations of fossil frogs may have been maintained in an environment that

experienced more equable climates that of today.

Detailed documentation of stratigraphic and sedimentologic aspects of

fossil deposits allowed interpretation of depositional environments.

Depositional systems in the catchment included channel and overbank type

deposits. Such deposits have variable taphonomic signatures, and those that

were identified were critical for identifying certain types of bias in the fossil

record. Sedimentological data also revealed information regarding

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palaeocurrent directions and allowed differences between stratigraphic units

to be qualitatively assessed. Documentation of stratigraphic horizons of

Kings Creek deposits allowed litho- and biostratigraphic correlations to be

made between sites QML796 and QML1396. Additionally, sedimentary

structures and taphonomic signatures indicated seasonally arid conditions in

the late Pleistocene catchment.

Taphonomic analyses also helped discriminate the provenance of

vertebrate and non-vertebrate material prior to deposition and constrained

the sampling area of the Kings Creek catchment. Taphonomic analyses

allowed for the documentation of the degree of autochthonous and

allochthonous components of the assemblages. Many unidentifiable bone

shards and ‘bone pebbles’ are variably abraded and experienced varying

degrees of transport and possibly multiple cycles of reworking. However,

identifiable bones analysed for palaeoenvironmental analyses suggest that

that material was derived proximal to the final point of deposition, and that

fluvial transport was minimal. Such an interpretation is consistent with the

small Pleistocene catchment size. Taphonomic analyses also revealed

several biases that may be related to the differential preservation of different

vertebrate groups. Several of those biases have not previously been

documented (e.g., preservation of agamids versus scincids), and hence, the

taphonomic significance of such bias is unclear. Taphonomic analyses

allowed for the meaningful comparisons of assemblages between

stratigraphic horizons at varying temporal and spatial scales.

The combined investigation of stratigraphic, sedimentologic, taphonomic

and palaeoecologic aspects of the deposits allowed for high resolution

documentation of late Pleistocene habitats and interpretation of

environmental change. Of critical importance is the occurrence of several

superposed assemblages at localities QML796 and QML1396, with

stratigraphically definable sequences that allowed recognition and

interpretation of temporal changes in the local faunas. Unfortunately, at site

QML1396, it could not be determined if the rarity of megafauna in the upper

horizon was due to local extinction or to a bias in accumulation due to

differential sorting during deposition of the overbank deposits. However, at

site QML796, decreasing diversity was shown not to reflect sample or

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taphonomic bias. At QML796, the creek appears to have sampled a

progressively more open-type environment from older to younger

assemblages. Such changes were detrimental to the persistence of several

taxa in the region and resulted in decreasing faunal diversity over the period

of deposition. Significantly, the temporal decrease in megafaunal diversity

was a gradual process. Faunal changes were likely related to species habitat

preferences rather than other factors, such as body size. Taxa recorded in

the youngest stratigraphic units were those that have habitat preferences for

open areas, or are common in a variety of habitats. Additionally, several taxa

recorded in the Darling Downs fossil record that are extant in the region

today are those taxa that have non-specific habitat requirements (e.g.,

Limnodynastes tasmaniensis, Tachyglossus sp., and Perameles nasuta).

There is no evidence for human-megafauna interaction on the Darling

Downs during the late Pleistocene, and the post parsimonious hypothesis is

that habitat changes and species extinctions were climatically driven.

Dating analyses indicate that the deposits are late Pleistocene in age.

However, the results from different dating methods are not in agreement with

each other. Determining an accurate chronology of deposition is one of the

most important aspects of the entire study, but has proven to be problematic.

Regardless, the dating results have very important implications regarding

megafaunal extinction.

MEGAFAUNA EXTINCTION HYPOTHESES

Based on the preceding comprehensive analyses that combined dating,

lithofacies, depositional environment, taphonomic, and palaeoecologic

analyses, it is possible to directly compare the results of this study to the

numerous existing hypothetical megafaunal extinction models.

Anthropogenic models

Blitzkrieg / Overkill

Most overkill hypotheses suggest that megafauna extinctions took place

rapidly (blitzkrieg <500 years; generalised overkill ~1,500 years) following

initial human colonisation (Whittington & Dyke, 1984; Barnosky et al.,

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2004b). U/Th and radiocarbon dating of Darling Downs megafauna deposits

suggest that deposition occurred either 88-55 ka or 45-36 ka respectively.

Stratigraphic and taphonomic data indicate minimally, a two-stage (i.e.,

progressive) extinction of Darling Downs megafauna (with some megafaunal

taxa still present in the youngest units). Collectively, those data suggest that

an attritional, rather than catastrophic, extinction event occurred in the late

Pleistocene Darling Downs over an extended period of time (i.e, 9-33 ka).

Although the timing of human arrival in Australia remains controversial

(O’Connell & Allen, 2004), the long time intervals of deposition established in

this study, although currently imprecise, unequivocally rule out blitzkrieg and

generalised overkill extinction for the majority of late Pleistocene Darling

Downs megafauna.

Prideaux (2004) proposed an attritional overkill extinction hypothesis

where increasing human hunting pressure over periods of ~20 000 years

eventually led to megafauna extinction. Although Darling Downs megafauna

extinctions were attritional, there is no direct evidence supporting the role of

humans in the extinction. The taphonomic component of the study

conclusively demonstrated that the accumulations were not via

anthropogenic pathways. The accumulations are typically fluvial in origin and

cut marks on bone are related to predation or scavenging by non-hominid

species (predominantly Thylacoleo carnifex). Additionally, there were no

anthropogenic cultural artefacts recovered from any of the deposits

investigated. Based on the current evidence, and allowing for the findings

from archaeological sites in the study area (e.g., Gill, 1978), the megafauna

deposits pre-date the first record of humans in the region by at least 30-35

thousand years.

Sitzkrieg

Sitzkrieg extinction hypotheses suggest that indirect anthropogenic-related

factors such as the introduction of predators/competitors and land

management techniques (e.g., fire use) eventually led to: 1) increased

competition between native species; 2) increased predation on native

species; and 3) loss of preferred habitats of endemic faunas (Diamond,

1989b; Barnosky et al., 2004b). Such changes had the potential to cause

247

faunal extinctions (Worthy & Holdaway, 2002). However, It is unknown

whether Pleistocene humans directly or indirectly introduced non-endemic

taxa into Australia. Hence, anthropogenically introduced predator/competitor

hypotheses cannot be tested here.

Although controversial, indirect, late Pleistocene anthropogenic land

management practices, such as burning, have been suggested for some

areas of Australia (Bowman, 1998; 2002; Wang et al., 1998; Luly, 2001;

Turney et al., 2001). However, the paucity of charcoal in the Pleistocene

Darling Downs fossil record does not support burning as a significant factor

in the palaeoenvironment. Some modern taxa that occurred in the

Pleistocene Darling Downs have extant populations that prefer vegetative

mosaics that are maintained by periodic burning (e.g., Isoodon obesulus).

However, it appears that fire may not have necessarily played a significant

role in maintaining Pleistocene Darling Downs vegetative mosaics.

Alternatively, Pleistocene Darling Downs vegetative mosaics may have been

maintained by feeding habits of megaherbivores such as Diprotodon sp. and

Zygomaturus sp. (cf., Owen-Smith, 1987; 1988; Zimov et al., 1995), and/or

equable climates (cf., Lundelius 1983; 1989).

Hyperdisease

The hyperdisease extinction hypothesis suggests that megafauna were

susceptible to virulent diseases introduced by initial human colonisers, either

directly or with species that accompanied them (MacPhee & Marx, 1997;

Fiedel, 2005). Large-sized taxa may be more susceptible to disease than

small-sized taxa (MacPhee & Marx, 1997; Fiedel, 2005). However, the local

extinctions of Pleistocene Darling Downs taxa do not appear to have been

specifically related to body-size, nor to specific taxonomic groupings. Rather,

species habitat preferences appear to have been the major factor influencing

the disappearance of taxa in the fossil record. Therefore, the hyperdisease

hypothesis is not supported for the extinction of Pleistocene Darling Downs

megafauna.

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Climate models of extinction

Co-evolutionary disequilibrium model

Coevolution refers to the evolution of multiple taxa that share close

ecological relationships and develop close interactions during times of

environmental stability (Graham & Lundelius, 1984). Perturbations such as

climate change can disrupt coevolved communities and result in

individualistic responses in species, causing ecosystems to significantly

restructure (Barnosky, 2001). The coevolutionary disequilibrium model

suggests that late Pleistocene climatically-driven ecosystem changes: 1)

disrupted the equilibrium of coevolved communities, 2) reduced niche

differentiation; 3) increased species competition; and 4) eventually led to

species extinction (Graham & Lundelius, 1984). Individualistic responses of

species were not restricted to particular taxonomic groupings, body-size or

ecological categories. A major difficulty in postulating the effects of such

climatic change and its effects on Pleistocene communities is the general

lack of knowledge of the interaction of species in the past.

Several extant taxa that are allopatric today occurred sympatrically in the

Pleistocene Darling Downs. Such ‘non-analogue’ assemblages of extant taxa

suggest that the Pleistocene Darling Downs may have had a more equable

climate than occurs today and a greater range of habitat niches to support

such populations. For example, assemblages of Isoodon obesulus,

Perameles bougainville and Pe. nasuta are allopatric today, but were

recorded in a single, discrete stratigraphic horizon at QML796. Extant

populations of I. obesulus occur throughout southern Australia and far north

Queensland; Pe. bougainville, occurred throughout southern central

Australia in historic times, but is presently restricted to islands of the Western

Australia coast; and Pe. nasuta is extant on the Darling Downs and the

eastern margin of Australia. That suggests that since the late Pleistocene,

each of those species moved independently of each other. Although such a

conclusion in based on end points only (there is little information available

regarding species distributions between the Pleistocene and initial European

colonisation), bandicoot distributions are consistent with the hypothesis that

species in the past, responded individualistically to environmental changes.

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The Darling Downs fossil record demonstrates that there was only a

minimal trend for taxonomic groups to adjust their geographic range (i.e.,

undergo local extinction) over the period of deposition (e.g., diprotodontoids).

Demonstrating the extinction of most taxonomic groups in the fossil record is

difficult due to low numbers of individuals and their apparent absence could

result from their initial rarity (e.g., Signor & Lipps, 1982). However, the

temporal loss of late Pleistocene taxa Darling Downs taxa is not correlated to

body size. Hence, data from the Darling Downs fossil record is consistent

with the co-evolutionary disequilibrium model of species extinction.

Mosaic-nutrient model

The mosaic-nutrient extinction model suggests that late Pleistocene climatic

changes disrupted seasonal regimes, decreased plant diversity and

increased zonation (Guthrie, 1984). That led to increasingly homogeneous

habitats and was detrimental to the persistence of mammal communities

resulting in: 1) less community diversity; 2) range contractions; 3) lowering of

body mass; and eventually 4) species extinction (Guthrie, 1984).

Pleistocene Darling Downs seasonal regimes were likely to have been

more equable than at present. The modern Darling Downs is highly seasonal

and experiences significant summer rainfall (Australian Bureau of

Meteorology). Although sedimentological data suggests that the late

Pleistocene Darling Downs climate was seasonal during the interval of

deposition, it is likely that seasonality increased markedly during the

approach of the last glacial maximum (Longmore & Heijnis, 1999; Hope et

al., 2004). Within the Darling Downs fossil record, it is evident that

Pleistocene habitats were becoming increasingly homogeneous over the

period of deposition, leading to decreased faunal diversity. Local extinctions

of several taxa were recorded in the deposit. However, geographic range

contractions of particular species are difficult to track using currently

available data, although several taxa clearly adjusted their ranges between

the late Pleistocene and present (e.g., Kyarranus sp., Ornithorhynchus

anatinus, Pseudomys gracilicaudatus). There was no obvious trend towards

decreasing body size of individual taxa, and that remains a difficult

hypothesis to test with high levels of statistical confidence considering

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relatively small sample sizes. Generally, there is some support for the

mosaic-nutrient extinction model for late Pleistocene Darling Downs

extinctions.

Multicausal or ecological models of extinction

Multicausal megafauna extinction models suggest that a combination of

climate changes and human interactions culminated in megafaunal extinction

(Calaby, 1976, Murray, 1991; Field & Dodson, 1999; Barnosky et al., 2004b;

Wroe, 2005; Boeskorov, 2006). Such hypotheses are difficult to test in the

absence of reliable chronologies of deposition. Current U-series and

radiocarbon chronologies suggest that the late Pleistocene Darling Downs

extinction phase took place between either 88-55 ka or 45-36 ka

respectively. If the growing consensus that humans arrived in Australia after

50 ka is correct (Fifield et al., 2001, Gillespie, 2002; O’Connell & Allen,

2004), the older U-series dates unequivocally suggest that the habitat

changes and species local extinctions occurred prior to human arrival in

Australia. If the earliest Australian humans did have an impact on the

extinction of the Darling Downs megafauna, they were simply compounding

on an extinction event all ready well underway. The younger AMS 14C dates

suggest that the late Pleistocene Darling Downs habitat changes and

species extinctions occurred after humans arrived in Australia. Correlation of

independent climatic data with the radiocarbon chronologies support the

timing of the interpreted habitat changes 45-36 ka. However, stratigraphic,

sedimentologic, taphonomic and palaeoecologic data suggest that such

changes may have occurred irrespective of potential human involvement.

Keystone herbivore model

Keystone species are megaherbivores that are immune to non-human

predation effects, and hence, can maintain large population sizes that can

radically affect vegetation structure (Owen-Smith, 1987; 1988; Sinclair,

2003). Removal of keystone species via naturally-driven climatic factors or

hunting can promote irreversible changes to plant communities (Owen-

Smith, 1987, 1988; Zimov et al., 1995). The keystone herbivore extinction

hypothesis relies on the fact that the first megafauna that disappear are

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keystone species. Within the late Pleistocene Darling Downs, the two largest

megaherbivores, Diprotodon sp. and Zygomaturus sp., appear to have gone

extinct at slightly different rates, but were among the first taxa to disappear in

the fossil record. Although several smaller-sized taxa, likely dependent on

broadly similar habitat types, went extinct at similar rates, the hypothesis

cannot be rejected. However, as discussed above, there is no evidence to

support an anthropogenic component in the extinction of Pleistocene Darling

Downs megaherbivores.

Self-organised instability

The self-organised instability (SOI) hypothesis suggests that a combination

of increased post-Pliocene aridity, increased speciation, and immigration of

fauna from southeast Asia during the Pleistocene led to community instability

(Forster, 2003). Increases in the immigration of humans in the late

Pleistocene may also have increased the connectivity of other faunal

elements into Australia causing significant disruption to prevailing

communities and eventually resulted in species extinction (Forster, 2003).

Again, the SOI hypothesis is difficult to test using current imprecise

chronologies of late Pleistocene Darling Downs habitat changes and species

extinctions. To properly test the SOI hypothesis on the Darling Downs and

other regions, more reliably dated assemblages are needed from varying

spatial and temporal scales.

FUTURE DIRECTIONS

In general, more rigorous dating analyses are necessary to test the results

presented here from the Darling Downs. Additional work is required on the

analysis of the microstructure of the bivalves that were submitted for dating.

That may provide evidence for why the 14C dating results were so variable.

Additionally, portions of those individual bivalves that were dated using

AMS14C were also submitted for amino acid racemisation (AAR; C. Murray-

Wallace, University of Wollongong) and U/Th (Jian-xin Zhao, AQUIRE,

University of Queensland) analysis to test the validity of the AMS 14C results

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using independent methods. Unfortunately, the results of those analyses are

not yet available.

In addition to mollusc shells submitted for U/Th dating, calcrete samples

have already been submitted for dating using U/Th methods. However, the

calcretes have extremely high levels of detritus, and in combination with the

open-system behaviour of the calcrete, meaningful ages could not be

calculated (Zhao, pers. comm, March 2005). Detailed analysis of the

mineralogy of calcrete is required to assess its potential for dating in the

deposit. Calcretes may be suitable for U/Th dating only if: 1) micrite and/or

spar are the dominant components; 2) cathodoluminescense for those

phases are weak; 3) Fe and Al levels are low; and 4) Sr levels are close to

the average of the studied deposit (Mallick & Frank, 2002). Such was not the

case for the submitted samples.

A possibility for assessment of the bone U/Th dates is to use the Pike

(2002) method of ICP-MS profiling of U concentrations across the bone. That

method assesses the uptake history of U and can determine whether U

leaching occurred, or whether U was taken up early or late during the burial

history. Thus, a diffusion-adsorption model of U-uptake may be applied to

calculate U-series dates with improved reliability (Millard & Hedges, 1996;

Pike et al., 2002).

Material has also been collected for other independent dating methods in

order to test the AMS 14C and U/Th results. Sediment samples were

collected prior to the commencement of this study for OSL dating and were

submitted to R.G. Roberts, University of Wollongong. However, the samples

have not been processed and results are unavailable. Samples have also

been collected that may be suitable for dating using electron-spin resonance

(ESR) dating methods, but have not yet been submitted.

Overall, the detailed stratigraphic, sedimentologic, taphonomic,

palaeoecologic and dating analyses of Kings Creek catchment deposits

provide a foundation for future work on similar aspects of fossil deposits from

the entire region. However, several of the hypotheses presented in this study

can be tested in the absence of reliable dates. For example, more

independent site studies from more widely-spaced geographic areas, in

combination with palaeocatchment analyses, are required to test hypotheses

253

about the proximity of certain habitats to specific sites of fossil accumulation.

Also, previous hypotheses that suggested that the Darling Downs represents

only a single local fauna (i.e., Molnar & Kurz, 1997) can be assessed only

with detailed investigations of additional fossil deposits.

Future systematic collecting of fossil deposits should target the recovery of

both large and small-sized species in order to allow meaningful comparisons

to the results presented here. Such collecting must also involve the thorough

stratigraphic documentation of the fossil deposit so temporal changes in

communities can be documented at each locality. More detailed

stratigraphical and sedimentological work is also required both in the Kings

Creek catchment and other Darling Downs deposits to examine stratigraphic

relationships at more regional scales. Determination of taphonomic modes of

accumulation are required to assess the relative degree of bias between

fossil assemblages. Rarefaction and other statistical analyses on taxon

abundance data are useful for testing the potential of bias introduced by

differences in sample size. Additionally, comparative taphonomic

experiments are required to help elucidate factors relating to the differential

preservation of mammals versus non-mammals (e.g., squamates), and

within non-mammal groups (e.g., agamids versus scincids), in order to

explain patterns observed in the fossil record. Collectively, those methods

will assist in the meaningful comparison between different stratigraphic

horizons and reveal biases that may affect palaeoecological interpretations.

Most prevailing megafauna extinction hypotheses were developed on

continental and global scales. However, it is imperative to test such

hypotheses on local and regional scales, such as are represented by the

Darling Downs. Although current evidence does not provide unambiguous

support for any of the prevailing climate-driven megafauna extinction

hypotheses, there is currently no evidence implicating a role for humans in

Darling Downs megafaunal extinctions. Although it may be over-simplistic to

simply suggest that climate change drove Darling Downs megafaunal

extinction, new results obtained here are consistent with that hypothesis.

Additionally, this research highlights the need to expand the project over

wider temporal and spatial scales, thus allowing more specific testing of

human versus climate hypotheses and more precise determination of the

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operational details and mechanisms driving megafaunal extinction. It may be

the case that humans played a more significant role elsewhere, but there is

currently a paucity of data linking megafauna and human interactions.

Recent studies from other regions (e.g., Cuddie Springs) are beginning to

demonstrate that megafaunal extinctions occurred gradually against a

backdrop of climatic deterioration; any role of humans remains

undocumented (Trueman et al., 2005).

Another significant value of the Darling Downs fossil record is that a high

proportion of the identified taxa are extant. Such taxa may not necessarily

occur on the Darling Downs today, but they do occur in other areas of

Australia and New Guinea. That suggests that extant species have

undergone significant range adjustments between the Pleistocene and

present. Knowledge of how species responded to climatic changes in the

past is essential for the development of future conservation strategies

(Barnosky et al 2004a). However, there is currently a paucity of data

regarding Pleistocene distributions of extant Australian taxa. That is primarily

due to a lack of well documented deposits that have incorporated detailed

aspects of stratigraphy, taphonomy and dating. Future research should aim

to document the spatial and temporal extent of both extant and extinct

faunas from the entire continent, and that will lend support to the

development of detailed conservation strategies and highlight the potential

risks faced by specific extant species.

SUMMARY

Few significant Australian late Pleistocene megafauna sites have been

examined as thoroughly as some of those deposits presented in this study.

The attributes of the present study that stand out from most previous

investigations include: 1) the sites represent a crucial time interval, i.e., they

bracket some megafaunal local extinction; 2) the deposits were excavated in

such a way that multiple separate accumulations were recovered that

represent a known stratigraphic, and hence, temporal sequence; 3) the

excavation technique also allowed detailed sedimentologic studies with

informed taphonomic analyses; and 4) both large and small-sized taxa were

255

recorded through the processing of many cubic metres of sediment. The

strength of the palaeoecologic interpretations lie in their testability and the

congruence between stratigraphy, sedimentology, taphonomy. Results and

interpretations presented in this study highlight the significance of the fossil

deposits of the Darling Downs and their value for understanding late

Pleistocene species extinction and habitat change.

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CONCLUSIONS

1) Regional topography of the modern Kings Creek catchment serves as an

analogue for estimating the catchment size during the late Pleistocene

because it is bordered largely by regional and continental divides. The late

Pleistocene Kings Creek catchment was geographically small and faunal

elements could not have been transported into the deposits from distances

greater than 25-30 km. Hence, all recovered fossils were sourced from local

environments.

2) More than 70 taxa were identified in the deposits, including 35 taxa that

were previously unknown to have occurred in the Darling Downs fossil

record. In particular, many small-sized species including land snails, frogs,

skinks, agamids, dasyurids, bandicoots and rodents were identified in the

Darling Downs for the first time. Additionally, one new species (Perameles

sobbei Price) was formally identified and five other potentially new taxa were

left in open nomenclature (?Limnodynastes sp.; Kyarranus sp. 1 & 2;

Dasyurus sp.; Palorchestes sp.).

3) Fossil accumulation processes are dominated by high-energy channel

deposition and lower energy, episodic overbank deposition. An extensive

basal fossiliferous horizon representing a major channel at QML796 and

QML1396 is litho- and biostratigraphically correlated.

4) Fossil preservation ranges from articulated skeletons to disarticulated and

highly fragmented abraded remains. Accumulations were made by fluvial

processes and cut marks on bones were related to feeding by non-hominid

carnivores. Several biases were identified relating to the differential

preservation of different skeletal elements and/or taxa. Assemblages are

dominated by small-sized taxa (i.e. <5 kg).

5) Palaeoclimate estimates based on small-sized taxa that occur in the

deposits indicate that the late Pleistocene Darling Downs climate was more

equable than present. Sedimentologic and taphonomic data suggest a

257

seasonally arid climate (e.g., abundant calcrete formation in an ephemeral

fluvial setting, and drought-like macropod mortality patterns).

6) Late Pleistocene Kings Creek catchment habitats included riparian

vegetation, vine thickets, scrubland, closed and open grassy woodlands, and

open grasslands. The late Pleistocene creek sampled an increasingly

homogeneous environment over the period of deposition. That reflected the

contraction of woodlands, scrublands and vine thickets, and expansion of

grasslands on the floodplain.

7) Several megafaunal taxa (e.g., Diprotodon sp., Troposodon minor,

Macropus agilis siva) suffered local extinctions over the period of deposition.

Other megafaunal taxa (e.g., Megalania prisca, Macropus titan, Protemndon

anak, P. brehus) persisted in the youngest units. Hence, those data suggest

minimally, a two-stage extinction of Darling Downs megafauna. Such

extinctions were not body-size specific, but rather, reflected species habitat

preferences.

8) U-series and radiocarbon dating indicate that the deposits are late

Pleistocene. However, an accurate chronology of deposition has not been

established due to discrepancies in the different dating methods.

Irrespective, the relative ages of significantly fossiliferous horizons at sites

QML796 and QML1396 are well established on the basis of superposition.

Additional dating is required to relate those horizons to fossiliferous horizons

at other sites, and such results may have significant implications relating to

the extinction of the Australian Pleistocene megafauna. Regardless, the data

allow a strict blitzkrieg hypothesis to be rejected because megafauna

extinction was not simultaneous in the Kings Creek catchment.

9) Comprehensive lithofacies, depositional environment, taphonomic, and

palaeoecologic analyses suggest that changing late Pleistocene Darling

Downs habitat and species diversity were most consistent with a climatically-

driven cause and occurred irrespective of potential human involvement.

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APPENDICES

Appendix 1. PRICE, G.J. 2002. Perameles sobbei sp. nov. (Marsupialia,

Peramelidae), a Pleistocene bandicoot from the Darling Downs, south-

eastern Queensland. Memoirs of the Queensland Museum. 48: 193-197.

This paper describes a new species of fossil bandicoot from the Pleistocene

Darling Downs.


I collected, prepared and identified the material that was examined in this

paper (with additional support from others noted in the Acknowledgements). I

also supervised the laboring efforts of the volunteers who assisted in the

preparation of fossil material. Additionally, I prepared the original and final

manuscript for publication.

307

308

309

310

311

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Appendix 2. PRICE, G.J. & HOCKNULL, S.A. 2005. A small adult Palorchestes

(Marsupialia, Palorchestidae) from the Pleistocene of the Darling Downs,

southeast Queensland. Memoirs of the Queensland Museum. 51: 202.

This paper describes an unusual occurrence of a small-sized megafauna

species in the late Pleistocene Darling Downs.


Scott A. Hocknull and I collected, prepared and identified the material that

was examined in this paper. I also supervised the laboring efforts of the

volunteers who assisted in the preparation of fossil material. Additionally, I

prepared the original manuscript for publication.

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A SMALL ADULT PALORCHESTES (MARSUPIALIA,PALORCHESTIDAE) FROM THE PLEISTOCENE OFTHE DARLING DOWNS, SOUTHEAST QUEENSLAND.Memoirs of the Queensland Museum 51(1): 202.Palorchestes is a rare component of the Australian fossilrecord with late Tertiary origins (Black, 1997). Severalspecies have been described, including; P. painei Woodburne1967 (Late Miocene); P. anulus Black 1997 (Late Miocene);P. selestiae Mackness 1995 (early Pliocene); P. parvus DeVis 1895 (Plio-Pleistocene); and P. azael Owen 1874(Pleistocene). Recent collecting from a late Pleistocenedeposit on the eastern Darling Downs, SEQ, recovered asmall dentary not referable to those species of Palorchesteswhere the dentary is known.

Family PALORCHESTIDAE Tate, 1948Palorchestes Owen 1873Palorchestes sp. (Fig. 1)

Material. QMF49455, edentulous right dentary. QML796,Kings Creek, near Clifton, eastern Darling Downs; latePleistocene (see Price, 2004).Description. Dentary broken anteriorly at I1 alveolus,posteriorly below M3 anterior alveolus; edentulous(excepting for in situ, broken, heavily worn protolophid ofM2); gracile, tapering anteriorly; anterior portion flaredbuccally; symphysis elongate, ankylosed; mental foramenanteroventral to P3; diastemal ridge well defined, linguallyoffset, concave lingually. Alveoli measurements in mm: P3:16.3L � 12.7W, M1: 18.6L � 10.9W; M2: 20.5L � 13.6W.Remarks. The dentary is referred to Palorchestes based onthe combination of its large size; presence of lophids; longand narrow symphysial region; gently tapered anterior; andbuccally flared diastema. The ankylosed symphysis, heavilyworn protolophid of M2 and presence of P3 alveoli indicatesthat the individual was an adult. Therefore, morphologicaldifferences between QMF49455 and other Palorchestesspecies are unlikely to be ontogenetic. Measurements ofalveoli suggest that the teeth were similar in size to P. parvus.However, QMF49455 differs from P. parvus, P. azael and P.painei by being more gracile with an anterior margin morebuccally flared; diastemal ridge better defined and linguallyconcave; and diastema proportionately shorter. Comparisonto P. selestiae and P. anulus is not possible as those speciesare known only from the M1. Black (1997) shows P. selestiaeto be markedly larger and P. anulus to be smaller than P.parvus. Hence, QMF49455 may represent an undescribed,

small species of Palorchestes or sexual dimorphism withinsmall-sized Palorchestes spp.Palorchestes spp. generally occur allopatrically showing atrend of increased body size from the mid Tertiary to the latePleistocene (Murray, 1991). QMF49455 is unusual in being asmall adult Palorchestes from the late Pleistocene. A secondspecies of Palorchestes, also recovered from QML796 andrepresented by a RI1, is referable to P. azael (QMF33024).Sympatry in Palorchestes spp. has been noted by Davis &Archer (1997), however, those occurrences may be due totemporally mixed faunas. Here we confirm sympatry of twoPalorchestes species during the late Pleistocene.Literature Cited.DAVIS, A.C. & ARCHER, M. 1997. Palorchestes azael (Mammalia,

Palorchestidae) from the late Pleistocene Terrace Site LocalFauna, Riversleigh, northwestern Queensland. Memoirs of theQueensland Museum 41: 315-320.

DE VIS, C.W. 1895. A review of the fossil jaws of the Macropodidaein the Queensland Museum. Proceedings of the LinneanSociety of New South Wales 10: 74-134.

BLACK, K. 1997. A new species of Palorchestidae (Marsupialia) fromthe late Middle to early Late Middle Miocene Encore LocalFauna, Riversleigh, northwestern Queensland. Memoirs of theQueensland Museum 41: 181-185.

MACKNESS, B. 1995. Palorchestes selestiae, a new species ofpalorchestid marsupial from the early Pliocene Bluff DownsLocal Fauna, northeastern Queensland. Memoirs of theQueensland Museum 38: 603-609.

MURRAY, P.F. 1991. The Pleistocene megafauna of Australia. Pp1071-1164 In Vickers-Rich, P., Monaghan, J.M., Baird, R.F. &Rich T.H. (eds) (Vertebrate Palaeontology of Australasia.Pioneer Design Studio; Lilydale, Victoria).

OWEN, R. 1874. On the fossil mammals of Australia- Part IX.Philosophical Transactions 164: 783-803.

PRICE, G. J. 2004. Fossil bandicoots (Marsupialia: Peramelidae) andenvironmental change during the Pleistocene on the DarlingDowns, southeastern Queensland, Australia. Journal ofSystematic Palaeontology 2(4): 347-356.

TATE, G.H.H. Results of the Archbold Expeditions. No. 59. Studieson the anatomy and phylogeny of the Macropodidae(Marsupialia). Bulletin of the American Museum of NaturalHistory 91: 235-351.

WOODBURNE, M.O. 1967. The Alcoota Fauna, central Australia: anintegrated palaeontological and geological study. Bureau ofMineral Resources, Geology and Geophysics, Bulletin 87.

Gilbert J. Price, Queensland University of Technology,School of Natural Resource Sciences, GPO Box 2434,Brisbane, Queensland; Scott A. Hocknull, QueenslandMuseum, 122 Gerler Road, Hendra, Queensland; 1 January2005.


FIG. 1. QMF49455, Palorchestes sp. right dentary. A, occlusal view. B, lateral view.

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Appendix 3. PRICE, G.J. 2005b. Pleistocene megafauna extinction: new

evidence from the Darling Downs, southeastern Queensland. Quaternary

Australasia. 23(1): 15-16.

This paper was an invited research report for Quaternary Australasia. It

provides a historical perspective of the research on the Pleistocene Darling

Downs, significance of the current findings with respect to megafauna

extinction, and possible future directions.


I researched and prepared the original and final manuscript for publication.

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QUATERNARY AUSTRALASIA 23 (1) 15

Debate concerning the extinction of the Australian Pleistocene megafauna has become polarised in recent years. Several proponents favour either climatic or anthropogenic megafauna extinction models. Critical to the debate is the development of accurate chronologies of initial human occupation and megafauna extinction. However, current imprecise and/or lacking chronologies are a contributing factor to the failure to resolve arguments about the causes of megafaunal extinctions. Additional deposits incorporating more complex and detailed ecological analyses and dating at different regional scales are required to resolve issues relating to megafauna extinction.

The Darling Downs, southeastern Queensland has enormous potential to help answer questions relating to megafauna extinction. The Darling Downs is particularly fossil-rich, with over 50 known megafauna-bearing fossil deposits in a small (16 000 km2) geographic area (Molnar and Kurz, 1997). Perhaps most importantly, the deposits may encompass the megafauna extinction episode in eastern Australia (Roberts et al., 2001). Previous palaeoenvironmental interpretations were primarily based on megafauna species occurring in the deposits and are suggestive of expansive grasslands with some woodlands (Molnar and Kurz, 1997). However, such interpretations are limited as few studies have addressed the documentation of detailed stratigraphic, sedimentologic and taphonomic aspects of the deposits. Additionally, past fossil collecting was biased towards the recovery of large-sized megafauna taxa. Small-sized forms are poorly known, thereby limiting previous palaeoenvironmental interpretations.

Recent studies of fossil deposits in the Kings Creek catchment, southern Darling Downs were aimed at incorporating detailed aspects of dating, stratigraphy, taphonomy and palaeoecology to establish a more accurate interpretation of the Pleistocene environment (Price, 2002, 2004; Price et al., 2005; Price andHocknull, 2005; Price and Sobbe, 2005).

RESEARCH REPORTS

Pleistocene megafauna extinction: new evidence from the Darling Downs, southeastern QueenslandGilbert J. PriceSchool of Natural Resource Science Queensland University of Technology ([email protected])

The Kings Creek catchment provides a unique opportunity to examine detailed palaeoecological aspects of a Pleistocene floodplain community in a small geographic area. Fossil accumulations within floodplains are typically transported, and it is commonly difficult or impossible to reliably constrain the sampling area of palaeodrainages. However, regional topography can be used to constrain the size of the Pleistocene Kings Creek catchment using the size of the modern catchment as an analogy. The Pleistocene catchment was relatively small, suggesting that fossil material could not have been transported over distances greater than 20-25 km. Thus, palaeoecological implications represent a small, well-constrained geographic area. Additionally, stratigraphic excavation techniques have allowed recovery of large collections of vertebrate remains that represent temporal sequences.

Radiocarbon dating indicates that the deposits are late Pleistocene (45-40 ka). Depositional processes in the catchment include both high-energy channel and low-energy vertical accretion deposits. Such depositional processes have a range of taphonomic signatures for both large- and small-sized vertebrates occurring in the deposits. Several biases have been observed relating to the differential preservation of mammals versus non-mammal vertebrates. Such biases may be related to fluvial sorting and/or density dependent destruction of different skeletal elements or taxa. Generally, identifiable material appears to have been derived from the surrounding proximal floodplain, an interpretation that is consistent with the geographically small Pleistocene catchment.

Systematic collecting methods targeted the recovery of invertebrates and both large- and small-sized vertebrates. Over 50 species were recovered from the deposits, including typical megafauna taxa (e.g. Megalania, Diprotodon, Protemnodon spp.) as well as new records of entire groups, such as land snails, frogs, skinks, and bandicoots. Most of the new records include extant species, and Pleistocene geographic

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range extensions have been documented for several of those taxa. Such assemblages suggest that the late Pleistocene Darling Downs climate was more equable than present, with more available water throughout the year.

Habitat interpretations based on the observed and inferred ecologies of Pleistocene Darling Downs taxa have increased the precision of previous palaeoenvironmental interpretations. A mosaic of habitats occurred on the Pleistocene floodplain including vine thickets, scrublands, open sclerophyllous woodlands interspersed with sparse grassy understories and open grasslands. However, at the time of initial European colonisation, open grasslands dominated the floodplain with woodlands confined closer to hillsides (Fensham and Fairfax, 1997). That suggests that significant habitat changes occurred since the late Pleistocene. Thus far, there is no specific evidence supporting an anthropogenic role in the contraction of late Pleistocene Darling Downs habitats or megafauna extinctions for several reasons. 1) There is no evidence of humans in the megafauna deposits (i.e. there are no cultural artefacts or human remains). 2) The charcoal record is poor suggesting that natural or anthropogenic firing of the Pleistocene landscape was insignificant. 3) Cut-markings on bones relate to feeding by non-human carnivores. 4) The megafauna deposits are 30-35 ka older than the first record of humans in the region. Other ecological and sedimentological data suggest that significant climate change occurred, possibly driving late Pleistocene Darling Downs habitat contractions and species extinctions, irrespective of potential human occupation.

Although it may be over-simplistic to suggest that climate change drove Darling Downs megafaunal extinction, this research highlights the need to expand the project over wider temporal and spatial scales. That will allow testing of human versus climate hypotheses and will more precisely determine the operational details and mechanisms driving megafaunal extinction. It may be the case that humans played a more significant role elsewhere, but there is currently a paucity of data linking megafauna and human interactions.

ReferencesFensham, R. J. and Fairfax, R. J. 1997. The use of the

land survey record to reconstruct pre-European vegetation patterns of the Darling Downs, Queensland, Australia. Journal of Biogeography 24: 827-836.

Molnar, R. E. and Kurz, C. 1997. The distribution of Pleistocene vertebrate on the eastern Darling Downs, based on the Queensland Museum collections. Proceedings of the Linnean Society 117: 107-134.

Price, G. J. 2002. Perameles sobbei, sp. nov. (Marsupialia, Peramelidae), a Pleistocene bandicoot from the Darling Downs, south-eastern Queensland. Memoirs of the Queensland Museum 48: 193-197.

Price, G. J. 2004. Fossil bandicoots (Marsupialia, Peramelidae) and environmental change during the Pleistocene on the Darling Downs, southeastern Queensland, Australia. Journal of Systematic Palaeontology 4: 347-356.

Price, G. J. and Hocknull, S. A. 2005. A small adult Palorchestes (Marsupialia, Palorchestidae) from the Pleistocene of the Darling Downs, southeast Queensland. Memoirs of the Queensland Museum 51: 202.

Price, G. J. and Sobbe, I. H. 2005. Pleistocene Palaeoecology and environmental change on the Darling Downs, southeastern Queensland, Australia. Memoirs of the Queensland Museum 51: 171-201.

Price, G. J., Tyler, M. J. and Cooke, B. N. 2005. Pleistocene frogs from the Darling Downs, southeastern Queensland, Australia, and their palaeoenvironmental significance. Alcheringa 29: 171-182.

Roberts, R. G., Flannery, T. F., Ayliffe, L. K., Yoshida, H., Olley, J. M., Prideaux, G. J., Laslett, G. M., Baynes, A., Smith, M. A., Jones, R. and Smith, B. L. 2001. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago. Science 292: 1888-1892.

RESEARCH REPORTS

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Documents

Pleistocene Palaeoecology of the Eastern Darling Downs · Darling Downs, southeastern Queensland, Australia, were examined in detail to establish an accurate, dated palaeoecological