Jurnal of o Paleontology - Monash University · Body mass estimations and paleobiological inferences on a new species of large Caracara (Aves, Falconidae) from the late Pleistocene

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1 Patricia Vickers-rich, andrey yu. Ivantsov, Peter W. trusler, guy m. narbonne, mike Hall, siobhan a. Wilson, Carolyn greentree, mikhail a. fedonkin, David a. elliott, Karl H. Hoffmann, and gabi I. C. schneider

Reconstructing Rangea: new discoveries from the Ediacaran of southern Namibia

16 James C. BrowerPaleoecology of echinoderm assemblages from the Upper Ordovician (Katian) Dunleith Formation of northern Iowa and southern Minnesota

44 rimma r. Khodjanyazova and Vladimir I. DavydovLate Moscovian fusulinids from the “N” Formation (Donets Basin, Ukraine)

69 timothy P. topper, Christian B. skovsted, David a. t. Harper, and Per ahlberg A bradoriid and brachiopod dominated shelly fauna from the Furongian (Cambrian) of Västergötland, Sweden

84 Henning scholz and matthias glaubrechtShell and operculum taphonomy of the bithyniid gastropod Gabbiella in the Pleistocene Turkana Basin, north Kenya

91 Dermeval aparecido Do Carmo, João Carlos Coimbra, robin Charles Whatley, lucas silveira antonietto, and raphael teixeira De Paiva Citon

Taxonomy of limnic Ostracoda from the Alagamar Formation, middle–upper Aptian, Potiguar Basin, northeastern Brazil

105 thomas saucede, alain Bonnot, Didier marchand, and Philippe CourvilleA revision of the rare genus Cyclolampas (Echinoidea) using morphometrics with description of a new species from the upper Callovian of Burgundy (France)

123 Vladimir n. makarkin and s. Bruce archibaldA diverse new assemblage of green lacewings (Insecta, Neuroptera, Chrysopidae) from the early Eocene Okanagan Highlands, western North America

147 Phil r. Bell, federico fanti, John acorn, and robin s. sissonsFossil mayfly larvae (Ephemeroptera, cf. Heptageniidae) from the Late Cretaceous Wapiti Formation, Alberta, Canada

151 Washington Jones, andrés rinderknecht, rafael migotto, and r. ernesto BlancoBody mass estimations and paleobiological inferences on a new species of large Caracara (Aves, Falconidae) from the late Pleistocene of Uruguay

159 michał Zaton , Paul D. taylor, and olev VinnEarly Triassic (Spathian) post-extinction microconchids from western Pangea

166 Jeffrey r. thompson, William I. ausich, and legrand smithEchinoderms from the Lower Devonian (Emsian) of Bolivia (Malvinokaffric Realm)

taxonomIC note

176 David m. rohr, Jirí frýda, and robert B. BlodgettAlaskodiscus, a new name for the Ordovician bellerophontoidean gastropod Alaskadiscus Rohr, Frýda and Blodgett, 2003

Journal of PaleontologyVOLUME 87 ■ NUMBER 1 ■ JANUARY 2013 ■ ISSN 0022-3360

Vol 87 no 1 January 2013 tHe PaleontologICal soCIety

RECONSTRUCTING RANGEA: NEW DISCOVERIES FROM THE EDIACARANOF SOUTHERN NAMIBIA

PATRICIA VICKERS-RICH,1 ANDREY YU. IVANTSOV,2 PETER W. TRUSLER,1 GUY M. NARBONNE,3 MIKEHALL,1 SIOBHAN A. WILSON,1 CAROLYN GREENTREE,1 MIKHAIL A. FEDONKIN,2 DAVID A. ELLIOTT,1

KARL H. HOFFMANN,4 AND GABI I. C. SCHNEIDER4

1School of Geosciences, Monash University, Clayton, Vic. 3800, Australia, ,[email protected].; 2Paleontological Institute, Russian Academy ofSciences, Profsoyuznaya ul. 123, Moscow 117997, Russia, , mfedon@paleo. ru.; 3Department of Geological Sciences and Geological Engineering,Queens University, Kingston, Ontario, Canada, ,[email protected].; and 4Namibian Geological Survey, Ministry of Mines and Energy,

Windhoek, Namibia, ,[email protected].

ABSTRACT—Rangea is the type genus of the Rangeomorpha, an extinct clade near the base of the evolutionary tree of large,complex organisms which prospered during the late Neoproterozoic. It represents an iconic Ediacaran taxon, but therelatively few specimens previously known significantly hindered an accurate reconstruction. Discovery of more than 100specimens of Rangea in two gutter casts recovered from Farm Aar in southern Namibia significantly expands this data set,and the well preserved internal and external features on these specimens permit new interpretations of Rangea morphologyand lifestyle. Internal structures of Rangea consist of a hexaradial axial bulb that passes into an axial stalk extending thelength of the fossil. The axial bulb is typically filled with sediment, which becomes increasingly loosely packed and porousdistally, with the end of the stalk typically preserved as an empty, cylindrical cone. This length of the axial structure formsthe structural foundation for six vanes arranged radially around the axis, with each vane consisting of a bilaminar sheetcomposed of a repetitive pattern of elements exhibiting at least three orders of self-similar branching. Rangea was probablyan epibenthic frond that rested upright on the sea bottom, and all known fossil specimens were transported prior to theirfinal burial in storm deposits.

INTRODUCTION

THE EDIACARAN frond Rangea Gurich, 1930 was the first largeand complex Precambrian fossil named and described

anywhere in the world, and remains an iconic image of theEdiacara biota. Rangea is a centimeter- to decimeter-scale frondconsisting of several ‘vanes’ or ‘petaloids’ (sensu Jenkins, 1985;Laflamme and Narbonne, 2008a, 2008b) that radiate from theaxis with each vane consisting of a sheet of elements composedof a repetitive pattern of self-similar branches. In the centurysince its original discovery in 1908, Rangea has been studied bymany Ediacaran researchers but remains enigmatic. Estimates ofthe number of vanes in Rangea have ranged from two (Gurich,1930, 1933; Richter, 1955) to three (Grazhdankin and Seilacher,2005) or three pairs (Pflug, 1972) to four (Dzik, 2002) to five(Pflug, 1970; Jenkins, 1985) and possibly six (Pflug, 1972).Rangea is normally reconstructed as an epibenthic frond(Richter, 1955; Pflug, 1970; Jenkins, 1985; Dzik, 2002;Laflamme et al., 2009) but was interpreted as living infaunallyby Grazhdankin and Seilacher (2005). Early interpretations ofRangea regarded it as representing a primitive example of livingradial phyla, either Ctenophora (Gurich, 1930, 1933) or Cnidaria(Richter, 1955), but with rare exceptions (Jenkins, 1985; Dzik,2002) most modern workers regard Rangea and other rangeo-morphs as members of an extinct clade in the early evolution ofcomplex multicellular life (Pflug, 1972; Seilacher, 1992, 2007;Narbonne, 2004; Brasier and Antcliffe, 2004; Gehling andNarbonne, 2007; Xiao and Laflamme, 2009; Erwin et al., 2011).

The first Rangea specimens were collected from Namibiaearly in the twentieth century (Germs, 1972, 1973) and werelater formally described by Gurich (1930, 1933). All of therelatively few (,21) Rangea specimens collected in Namibiabefore 2004 were found as float by either herders or mappinggeologists and later turned over to paleontologists for study. Afew specimens of Rangea have also been described from theWhite Sea in Russia (Grazhdankin, 2004; Grazhdankin andSeilacher, 2005), but the genus is not known from any other

Ediacaran fossil localities (Xiao and Laflamme, 2009). Thistaxon is not known from Newfoundland, and the singlespecimen reported from the Flinders Ranges of South Australia(Gehling, 1991, pl. 3, fig. 1) was subsequently referred to thegenus Beothukis Brasier and Antcliffe, 2009 due to the presenceof primary elements that consistently show only one side of therangeomorph structure (Narbonne et al., 2009). The relativelysmall number of quite variable specimens of Rangea hassignificantly impeded determination of its life habit and three-dimensional reconstruction, leading to the many differentinterpretations noted above.

Two sedimentary concentrations totaling more than 100complete and partial specimens of Rangea are herein reportedfrom Farm Aar in southern Namibia (Fig. 1). The originaldiscovery was from float (Vickers-Rich, 2007, fig. 116), withadditional discoveries of float and abundant in situ materialmade by the authors over the following years. Fossils wereexcavated under permits from the National Heritage Council ofNamibia, and specimens are deposited with the GeologicalSurvey of Namibia, National Earth Science Museum (NESM) inWindhoek. These new specimens increase the Rangea dataset bya factor of five and exhibit a unique style of preservation thatpermits some investigative preparation, revealing previouslyunknown internal features and significantly enhancing ourunderstanding of Rangea and its place in the early evolutionof complex macroscopic life.

GEOLOGICAL AND ENVIRONMENTAL SETTING

The Nama Group is a 3-km thick succession of generally flat-lying, fine-grained siliciclastic and carbonate strata that non-conformably overlie Mesoproterozoic basement in southernNamibia (Fig. 2.1). Nama Group strata were deposited andslightly deformed in a foreland basin that developed duringcollision of the Damara and Gariep structural belts in the lateEdiacaran and early Cambrian, and have been divided into threesub-groups reflecting this progressive orogenesis (Germs, 1983;

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Journal of Paleontology, 87(1), 2013, p. 1–15

Copyright � 2013, The Paleontological Society

0022-3360/13/000187-0001$03.00

Grotzinger and Miller, 2008). The Kuibis Subgroup consists ofup to 200 m of mature siliciclastics and carbonates representingcratonogenic and early foreland basin deposits. The overlying1200-m thick Schwarzrand Subgroup mainly consists of distalflysch and carbonates deposited in shallow-marine environ-ments. The Nomtsas Formation capping the SchwarzrandSubgroup and the overlying Fish River Subgroup are made upof shallow marine and non-marine molasse reflecting fill of aforeland basin. The Kuibis and Schwarzrand subgroups containabundant Ediacara-type fossil impressions and remains, withcarbon-isotope stratigraphy and precise U-Pb dates of 547–541Ma derived from volcanic ash beds providing further support fora late Ediacaran age, whereas the unconformably overlyingNomtsas Formation hosts Cambrian-type trace fossils and hasyielded an early Cambrian radiometric date of 538 Ma (Germs,1972; Grotzinger et al., 1995; Narbonne et al., 1997; Abelson etal., 2012; Schmitz, 2012; Narbonne et al., 2012).

The newly discovered specimens of Rangea reported in thispaper occur in the upper part of the Kliphoek Member of theDabis Formation within the Kuibis Subgroup (Fig. 2.1, 2.2).This unit, particularly the lower part, has previously yieldedabundant Ediacara-type fossil impressions, including those ofPteridinium, Ernietta, Nemiana and, less commonly, Rangea atmultiple levels throughout the member (Germs, 1972; Saylor etal., 1995). The Kliphoek and the overlying Mooifonteinlimestone collectively form a single depositional sequence (K2of Saylor et al., 1995, 1998; Grotzinger and Miller, 2008). Insouthern Namibia, the top of K2 is erosionally overlain by thebasal strata of the Schwarzrand Group, but additional sequencesare present in the upper Kuibis Subgroup north of the Osis Arch.The overlying sequence (K3) contains a volcanic ash that has

yielded a precise U-Pb date of 548.861 Ma (Grotzinger et al.,1995; Saylor et al., 1998, 2005), subsequently revised to547.3260.65 Ma (Schmitz, 2012; Narbonne et al., 2012),providing a minimum age for the Rangea fossils in the presentstudy.

Saylor et al. (1995, 1998) and Grotzinger and Miller (2008)described the environmental succession of the Kliphoek andMooifontein members. Desiccation cracks or other evidence ofemergence are strikingly absent from both the Kliphoek andMooifontein members, and imply subaqueous depositionthroughout the entire sequence. Basal Kliphoek strata belowthe fossiliferous levels are lowstand deposits consisting ofmainly thick-bedded, coarse-grained quartzarenites with abun-dant meter-scale trough cross-bedding. Deposition may haveoccurred in a sandy braided fluvial or more likely in a high-energy nearshore or deltaic setting. The upper 70 cm of thecontinuous sandstone within the lower part of the KliphoekMember consists mainly of fine-grained quartzarenite withsyneresis cracks and/or sandstone injection structures, current-and combined-flow-ripplemarks, and hummocky cross-stratifi-cation. These strata contain abundant impressions of Pteridi-

nium and Ernietta and a single specimen of Rangea. Above thissandstone, the upper part of the Kliphoek Member, whichcontains the new fossil occurrence in addition to previouslyreported specimens of Pteridinium, Ernietta, and Nemiana,

FIGURE 2—Stratigraphic setting of the newly discovered Rangea specimenson Farm Aar, Namibia: 1, complete Nama Group stratigraphy in the WitputsSub-basin, asterisk indicates date correlated from Zaris Sub-basin; 2,stratigraphy on Farm Aar, showing stratigraphic units and fossiloccurrences; ZFM¼Zaris Formation. Revised U/Pb dates from Schmitz(2012).

FIGURE 1—Location of the newly discovered Rangea specimens on FarmAar, Namibia.

2 JOURNAL OF PALEONTOLOGY, V. 87, NO. 1, 2013

consists of transgressive gray-green shale and siltstone withsporadic interbeds of very fine- to fine-grained, centimeter-scalesandstone event beds that are laterally discontinuous overdecameter scales. Sandstone event beds are erosionally based.The lower part of each event bed consists of parallel-laminatedsandstone reflecting upper-flow regime plane beds, which isovertopped by sandstone exhibiting hummocky cross-stratifica-tion, wave ripples, or combined-flow ripples. Centimeter-scalerip-up clasts of shale and/or microbialite also occur commonlyin the upper half of these event beds. These features arediagnostic of storm beds modified by wave processes during thewaning flow stage, and imply deposition slightly below fair-weather wave-base on a muddy ramp (Myrow, 1992; Myrowand Southard, 1996; Plint, 2010). Shallow-water limestones withhummocky and swaley cross-stratification, intraclastic textures,and microbial textures first appear approximately 3 m above thenew Rangea occurrence (Fig. 2.2). Laminated carbonates,locally containing cross-bedded ooids and the shelly fossilCloudina, dominate the overlying Mooifontein Member andimply shallow-water deposition during highstand conditions tothe top of the K2 sequence.

In summary, these data imply that the Rangea specimens ofthis study were preserved in a muddy mid-ramp setting justbelow normal wave-base, an environment with gentle wave andcurrent action and periodic disturbance by major storms. Thesefeatures also imply that the sea bottom was probably within thephotic zone. This environmental interpretation is broadly similarto that postulated for other Ediacaran fossil occurrences in theKuibis (Grazhdankin and Seilacher, 2002, 2005; Bouougri et al.,2011) and Schwarzrand (Narbonne et al., 1997) subgroups ofNamibia and many others worldwide (Grazhdankin, 2004).

NEW RANGEA OCCURRENCE

A concentration of more than 100 specimens of Rangea wasdiscovered along the dirt track leading from Highway B4 toFarm Aar 16, approximately 8 km east of Aus in south-westernNamibia (locality 1 in Fig. 1). The original discovery was infloat dislodged during road maintenance (Vickers-Rich, 2007,fig. 116), which led to the location of abundant in situ materialas well as further float specimens during the following years. Insitu specimens were collected from a flat-bottomed gutter castwith its top located 35–40 cm above the upper boundary of thecontinuous sandstones of the lower Kliphoek Member (Fig. 2.2).A larger, but less fossiliferous concentration was discovered in asimilar gutter cast at the same stratigraphic level 2.6 km to thesouth-west (locality 2 in Fig. 1).

The fossiliferous gutter casts are gentle- to steep-sided (20–758 slopes), mainly flat-bottomed, 35–100 cm wide and 5–10 cmdeep (Fig. 3). The walls and floor of these gutter casts arelocally adorned with tool marks, oriented broadly parallel withits axis. The highly sinuous nature of the gutter casts and theabsence of flutes or other directional indicators, however,preclude accurate determination of the direction of flow. Rangeasite 1 occurred in a gutter cast 38–55 cm wide with an exposedlength of 1.2 m and a maximum depth of 10 cm, oriented at 120/3008Az. (Fig. 3.1, 3.2). Rangea site 2 was a complex of at leasttwo partially overlapping and cross-cutting, flat-bottomed guttercasts (Fig. 3.3, 3.4) The largest is a sinuous channel at least 3.7m long (incomplete at the east end), which is 35–45 cm wideand 7 cm deep in its central region but flares to more than ameter in width at either end with a maximum thickness of 5 cmin the widened section. It partly overlaps and partly cuts asimilar but smaller channel at least 33 cm wide trending 045/2258Az. Each gutter exhibits a bipartite fill similar to that of thestorm event beds in the section (Fig. 3.2). The lower half

consists of unfossiliferous, finely laminated, fine-grained quartzsandstone, which is confined to the gutter cast. This is abruptlyoverlain by very fine-grained quartz sandstone with low anglehummocks and swales that fills the gutter casts and occasionallysteps beyond the erosional margins of the underlying channel,giving the fossiliferous lenses a somewhat irregular shape inplan view.

Thin intraclasts of mudstone and/or microbial sheets, cm-scale smooth and striated baglike fossils, and specimens ofRangea occur abundantly within these hummocky cross-stratified caps (Fig. 3.1, 3.3, 3.4). The Rangea specimens showa consistent orientation in a vertical sense, with the frond axisnearly horizontal and all edges slightly bowed upwards to forma convex-down, boat-shaped profile (Figs. 4.1–4.4, 5.2), aprofile that is typical of Rangea specimens worldwide(Grazhdankin and Seilacher, 2005).

RECONSTRUCTING RANGEA MORPHOLOGY

Virtually all previously described specimens of Rangea showonly a leafy petalodium, and consequently, the nature of thebase of Rangea and its internal organization, have been largelyunknown and quite controversial. Jenkins (1985, figs. 2c, 4b)and Dzik (2002, fig. 2B) regarded a single specimen(NESMF338-5; previously illustrated by Pflug, 1970, fig. 6Band pl. 34.5) as showing evidence for a sand-filled axial stalkabove a bulbous base, and incorporated these features in theirsomewhat different reconstructions of Rangea as an attachedfrond. However, Grazhdankin and Seilacher (2005) regardedthese features in NESMF338-5 as ‘‘fortuitous’’ and reconstruct-ed Rangea as consisting only of a leafy petalodium that grew inthe sediment.

The frondose petalodium of the new specimens from FarmAar is remarkably similar to the flattened (‘forma plana’ ofGurich, 1933) specimens of Rangea described by previousauthors. Uniquely, however, most of the new specimens exhibita hexaradial, bulb-like structure located proximally within theRangea frond that continues as a gently tapering cone axiallythroughout the entire length of the Rangea frond (Figs. 4.3–4.6,5.1–5.5, 6, 7, 8). These features are only rarely andcontroversially represented in previously described specimensof Rangea, and provide critical information for reconstructingthe morphology and lifestyle of this previously enigmaticEdiacaran fossil.

Most organic materials in the two fossiliferous gutter castswere replaced by or coated with a thin layer of pyrite variablypreserved as pyrite ‘‘death masks’’ (Gehling, 1999), and otherminerals that represent weathering products of pyrite: goethiteand other Fe-oxyhydroxide minerals (i.e., ‘‘limonite’’) andjarosite ([KFe3þ

3(SO4)2(OH)6]). The identification of jarositewas confirmed using powder X-ray diffraction (XRD). Jarositeis a common oxidative weathering product of pyrite (Jambor andBlowes, 1998; Lottermoser, 2010) in the presence of K-bearingsilicate minerals such as micas and K-feldspars (Bladh, 1982),which are abundant in the Farm Aar samples (Figs. 5.1, 6.1).These early diagenetic pyritic replacements/coatings of theorganic material of Rangea provide a mineralogical contrastbetween the fossils and the sedimentary rock in which they areentombed that further enhances recognition and study of thenewly discovered Rangea specimens from Farm Aar. Areconstruction of Rangea is presented in Figure 9.

Axial bulb and stalk.—In contrast with previously publishedspecimens of Rangea, most of which consist entirely of thepetalodium, effectively all specimens in this study show a threedimensional axial structure made up of a proximal axial bulb thatgrades distally into a conical stalk tapering to the tip of the

VICKERS-RICH ET AL.—RECONSTRUCTING RANGEA 3

FIGURE 3—Outline diagrams of fossiliferous channel deposits from Farm Aar in south-western Namibia: 1, top view of a specimen block sequence fromChannel 1 showing the horizontal distribution of fossils excavated from within the deposit and registered against the flow pattern (gray lines) as cast by the lowerchannel sediment unit, line of transverse section A–B, with specimen block numbers (F638–641) referring to the National Earth Science Museum (NSEM)


collection in Windhoek, scale bar¼10 cm; 2, reconstructed transverse section A–B across three blocks of Channel 1, lower sediment unit dark gray, uppersediment unit light gray, scale bar¼10 cm; 3, photograph of the excavated central part of Channel 2, arrow indicates excavated Rangea specimen NESMF659-b,scale bar¼50 cm; 4, outline of Site 2 Channel showing the horizontal distribution of fossils excavated from within the deposit and registered against the flowpattern (gray lines) as cast on the base of the channel, arrow indicates Rangea specimen NESMF659, scale bar¼50 cm.

FIGURE 4—Rangea schneiderhoehni (Gurich, 1930) preservation form. 1, 2, the boat-shaped preservation expressed in part and counter-part specimens: 1,upper view of concave down NESMF631-b, lower part; 2, lower view of convex down NESMF631-a, upper counter-part; 3, bottom view showing variety ofpreservation and exposure levels in three specimens of NESMF628; 4, outline diagram of NESMF628, original discovery specimen from Farm Aar, near Channel1, specimens 1–3, vanes shaded light gray, marginal tubes shaded mid-gray, axial fill shaded dark gray; 5, oblique profile view of NESMF628, specimens 1–3proximal regions; 6, outline diagram of NESMF628, specimens 1–3 proximal regions, vanes shaded light gray, marginal traces shaded mid-gray, axial fill shadeddark gray. All scale bars¼1 cm. Abbreviations: as¼axial stalk; av¼axial volume; em¼element midline; mt¼marginal tube.


FIGURE 5—Channel 1, Farm Aar, southern Namibia: 1, Rangea specimen and other fossil material NSEMF642-c showing jarosite coating; 2, profile ofNESMF641-b with specimen NESMF641-c confined to the upper channel unit, immediately above the boundary (arrowed) of the lower unit; 3, block


specimen (Figs. 4.3–4.6, 5.2–5.5, 6.1–6.4, 7, 8.1–8.3). Theproximal axial bulb is internally cast with sandstone which islithologically dissimilar to the very fine-grained sandstoneentombing the fossils, but is compositionally, texturally, anddiagenetically similar to the fine-grained sandstone layer whichforms the basal fill of the gutter cast several millimeters tocentimeters below the fossils (Fig. 5.3–5.6). This axial fillbecomes increasingly loosely packed and porous along the stalktowards the distal taper, which typically is preserved as an openvoid (Figs. 4.3–4.6, 6.1–6.4, 7.3, 7.4). This may well have beensoft tissue or liquid-filled in life. The frondose part of Rangea ispartially flattened, but the axial region has generally beenpreserved fully dimensional, with minimal distortion despite theabsence of axial fill by sandstone in the distal parts of thespecimen. This geometrical relationship is maintained even inspecimens in which the sandstone-filled axial bulb is strati-graphically higher than the open cylindrical stalk (Figs. 6.1–6.4,7.1–7.4), implying that a sandstone-filled axial bulb and anorganic-filled axial stalk may have been primary features of thespecimens from Farm Aar.

The axial bulb is lobate, with consistent hexaradial symmetry(Fig. 7.5–7.7). Undeformed bulbs whose axes lie perpendicular tobedding invariably exhibit six major lobes defined by shallowlongitudinal creases, with each major lobe further divided by afainter longitudinal crease that imparts a secondary hexaradialpattern. The confluence of the six major lobes at the proximalpole of the bulb commonly exhibits an axial node 4–10 mm(average 5 mm) in diameter, the function of which is unresolved(Figs. 6.3, 6.4, 7.3, 7.6. 8.5).

The hexaradial axial bulb at the base of a conical stalk has notpreviously been described from any specimen of Rangeaworldwide, and represents an important contribution of the newspecimens herein described. The smooth ‘‘ovate mass ofsediment’’ in specimen NESMF338-5 that Jenkins (1985)interpreted as a possible holdfast and Dzik (2002) termed a‘‘basal bulb’’ lacks hexaradial symmetry and lies proximal to therangeomorph frondose elements and a badly cracked and nearlyunrecognizable internal axial structure. This smooth ball may bean indistinct and badly preserved example of the hexaradial bulbor may be a fortuitous juxtaposition of different features asinferred by Grazhdankin and Seilacher (2005). Similarly, there isa featureless ovoid structure abutting the axial bulb ofNESMF636-f (Fig. 7.6). Neither NESM F338-5 nor any otherpreviously figured specimen of Rangea shows the hexaradialsandstone bulb that is so prevalent in the specimens of Rangeafrom Farm Aar.

The hexaradial axial bulb passes distally into a conical axialstalk (Figs. 5.2, 6.1–6.4, 6.7, 6.8, 7, 8.1, 8.3) with a circular cross-section and a gently distal taper. This axial stalk is evident inessentially every specimen of Rangea at Farm Aar but is notobvious in previously described specimens noted in the literature,which exhibit more traditional Rangea preservation. In thesepreviously known specimens, the axial stalk may be indiscernible(e.g., Jenkins, 1985, fig. 2A, 2E1) or represented by a flattenedtriangular region (the ‘‘median zone of flattening’’ of Jenkins,1985), which may (Jenkins, 1985, fig. 2D) or may not (Jenkins,

1985, fig. 2A) exhibit rangeomorph branching on the surface.Other authors have figured this triangular feature withoutcomment. We infer that a conical axial stalk was present beneaththe frondose rangeomorph structure in all of these specimens butwas partially collapsed in swollen (‘forma turgida’ of Gurich,1933) specimens and completely collapsed in flattened (‘formaplana’ of Gurich, 1933) specimens of Rangea.

Internal casts of the axial stalk imply that it was originallycircular in cross-section and lay horizontal to the bedding plane inthis preservation (Figs. 5.2, 6.7, 6.8), with its proximal portioncurving upwards towards the axial bulb (Figs. 5.2–5.5, 6.1–6.4,7.1–7.7). The highest level of the bulb is consistently higher thanthe stalk. The flexure between the horizontal stalk and the verticalbulb is marked with crescentic ridges that are arranged in analternating series on each side of the shallow creases. Where theaxial cast is upwardly curved at the ‘neck’ of the bulb, thelongitudinal markings are strongly evident on the ‘outer’curvature and the transverse crescents weakly so, but these forma more wrinkled surface on the ‘inner’ curvature. This impliesthat the flexure is not natural and more likely is a result ofdistortion of a flexible structure, probably a depositional or postmortem feature of collapse, compaction or contraction.

Petalodium.—The axial bulb and stalk are entirely internalfeatures that were completely surrounded by the petalodium ofRangea—a radial arrangement of elongate, semiovate vanes witheach vane exhibiting the self-similar branching diagnostic ofrangeomorph architecture (Figs. 4.3, 4.4, 6.1, 6.2, 7.1, 7.2, 8.1–8.3, 9). The preserved appearance of the Rangea petalodium hasbeen well described by all previous authors (Gurich, 1930;Richter, 1955; Pflug, 1970; Germs, 1973; Jenkins, 1985; Dzik,2002, Grazhdankin and Seilacher, 2005), although their structuralinterpretations vary. Rangea shows at least four orders of self-similar branching that we label in ascending order from thelargest (most visible) to the finest scale following the patternillustrated by Narbonne et al. (2009, fig. 2). The highest-level(primary) element consists of a bifoliate ovate sheet extending theentire length of the fossil, with its midline corresponding to themajor groove on the underlying hexaradial axial bulb (Figs. 7.5–7.7, 8.4, 8.5, 9). This midline serves as the origin for an array ofalternating major and subsidiary branches, estimated to number18–22 for each series (Figs. 4.3, 4.4, 6.1, 6.2, 7.1, 7.2, 9) thattogether constitute the second order series. Each second orderbranch is centimeter-scale and consists of a series of millimeter-scale secondary branches alternating along each side of itsmidline. Only three orders of branching are visible in mostRangea specimens, but Pflug (1970) described a possible fourthorder branching in one specimen. This is similar to therangeomorph fossils of Newfoundland, which typically showtwo orders of branching, centimeter-scale and millimeter-scale,but reveal up to four orders of self-similar branching in the bestpreserved specimens from Spaniard’s Bay (Narbonne, 2004;Narbonne et al., 2009).

Grazhdankin and Seilacher (2005) recognized an alternatingpattern of major and minor second order elements of Rangea andinferred an interdigitation of these branches to produce both sidesof the vanes. We concur with their observation of the alternatingsize of primary branches but differ in our interpretation of the

NESMF643 vertically sectioned transverse to channel showing various specimens (arrowed) within the upper channel unit; 4, detail of Rangea specimen in blockNSEMF643 (arrow on right in 3), shown in thin section under raking natural light (slightly oblique to specimen axis); 5, outline of thin section in 4, fill shadeddark for solid granular sediment, light shading for finer degraded sediment, jarosite layers in black lines, fill laminations in brown lines; 6, thin sections fromNESMF643 photographed with raking natural light, showing shallow gradation zone between lower and upper sediment units (marked by double arrow) andunidentified sectioned specimen enclosing fill different from surrounding upper channel sediment unit (arrowed). All scale bars¼1 cm. Abbreviations: ab¼axialbulb; af¼axial fill; as¼axial stalk; mt¼marginal tube.


FIGURE 6—Specimen NESMF643-b1, Farm Aar, Channel 1, with thin sections and line drawings illustrating external and internal structure: 1, lower surfaceshowing axial shaft flexed upwards (into matrix) at its proximal end, region of exposed axial fill proximal to the distal two-thirds of the shaft length is covered by


three-dimensional architectural structure. Fossil remains ofRangea now show concave relief of the primary branches (Fig.8.4). The reconstruction (Fig. 9) shows the concave relief restoredto a convex-out architecture by analogy with other rangeomorphs.Details of the architecture of Rangea from Farm Aar andelsewhere are currently under study and will be presentedseparately. In the interim, the architecture in Figure 9 is showngenerically as consisting of a self-similar series of convex-outlobes on both sides of each vane, consistent with previousinterpretations of Rangea and other rangeomorphs (Pflug, 1970;Jenkins, 1985; Seilacher, 1992; Dzik, 2002; Narbonne, 2004;Brasier and Antcliffe, 2004; Grazhdankin and Seilacher, 2005;Gehling and Narbonne, 2007; Flude and Narbonne, 2008,Narbonne et al., 2009; Laflamme et al., 2009).

Where the outer edge of a Rangea vane can be observed in planview, it is typically represented by a sharp marginal ridge (Fig.4.3, 4.4; see also Jenkins, 1985, fig. 2A, 2B; Grazhdankin andSeilacher, 2005, fig. 6b; Bouougri et al., 2011, fig. 4G). Variablepreservation of this margin in different specimens from Farm Aarimplies that it was a cylinder that extended the length of eachvane (Figs. 5.4, 5.5, 6.1–6.4, 6.7, 6.8, 7.1–7.4, 8, 9). Where thismarginal tube was sand-filled, it is cylindrical with a ridgedornamentation, but the marginal ridge could also be deflated andappear as a gutter-shaped feature.

Gurich (1930, 1933) and Richter (1955) regarded Rangea asbifoliate, based on limited material available at the time, but allsubsequent authors agree that Rangea is multifoliate (sensuLaflamme and Narbonne, 2008a, 2008b), consisting of three ormore vanes that join length-wise along their inner edge andradiate outwards from this axis. In most specimens the vanes werefolded flat upon each other during burial, with the multifoliatenature visible mainly through partial overlap of underlying vanes.As a consequence, the number of vanes in the Rangea petalodiumhas been difficult to determine with certainty. Based on specimenNESMF-540 and other material, Pflug (1970) and Jenkins (1985)suggested that there was evidence for five or more vanes. Pflug(1972) provided three reconstruction modes for Rangea, one ofwhich was pentameral and two showing differing arrangements ofthree pairs of branching structures, implying six vanes. Dzik(2002) recognized four vanes, and Grazhdankin and Seilacher(2005) regarded Rangea as consisting of only three vanes, apattern also seen in the erniettomorph Pteridinium (Pflug, 1970;Grazhdankin and Seilacher, 2002; Elliott et al., 2011). Five vanesare visible in several of the new specimens from Farm Aar,supporting the views of Pflug and Jenkins that Rangea is highlymultifoliate. Cross-sections of five vanes are preserved withequidistant spacing allowing for a sixth (Fig. 6.7, 6.8). Evidencefrom the bases of other specimens solidly demonstrates thepresence of six vanes, each emanating from one of the majorlobes of the axial bulb and extending up the side of the axialcolumn (Fig. 8). This association between the six vanes thatcharacterize the external Rangea petalodium and the six lobes ofits internal axial bulb provides a firm basis for reconstructing thethree-dimensional morphology of Rangea.

Reconstruction.—The morphologic features and relationshipsdescribed above permit a reconstruction that appears to beapplicable to the 100þ specimens of Rangea recovered from FarmAar and other specimens of Rangea worldwide (Fig. 9). Thisanalysis supports and augments aspects of Rangea morphologyproposed by previous workers, rules out some other pastinterpretations, and, most importantly, permits integration ofsome formerly disparate views into a unified reconstruction of theRangea organism.

The sandstone-filled hexaradial axial bulb present in most ofthe specimens from Farm Aar had not been previously reported inany specimens of Rangea, and represents a unique contribution tounderstanding Rangea morphology. Reconstruction of thisstructure and the axial stalk to which it was attached (Fig. 9)strongly supports Dzik’s (2002) view that the Rangea anatomyenveloped a voluminous and persistent axial space, whichtraversed the length of the organism and was integral to itsconstruction. It is also consistent with Pflug (1970) and Jenkins(1985) that the Rangea frond was highly multifoliate, andspecifically suggests that it had six vanes, which correspond tothe hexaradial symmetry in its axial bulb, with the edge of thevane inserting into each of the clefts in this bulb. The Farm Aarspecimens exhibit at least three orders of self-similar branching,consistent with the descriptions and illustrations of Gurich (1930,1933), Richter (1955), and all subsequent workers.

RECONSTRUCTING RANGEA LIFESTYLE AND TAPHONOMY

The new specimens of Rangea from Farm Aar are similar toall previously figured specimens of Rangea in being orientedsub-horizontally within or on the surface of sandstone beds.Bouougri et al. (2011, fig. 4H) figured a specimen theysuggested was embedded vertically within the sediment, butthis interpretation is not evident from their figure, which indeedappears to be preservation on a bedding plane. Most previousauthors have interpreted this horizontal orientation of Rangea asrepresenting transported and felled specimens of epibenthicfronds (Jenkins, 1985; Dzik, 2002), but Grazhdankin andSeilacher (2005) reinterpreted the present-day horizontalorientation of Rangea as reflecting in situ specimens that livedinfaunally.

The Farm Aar specimens of Rangea are scattered through theuppermost 25 mm of hummocky cross-stratified, fine-grainedsandstone, which caps the mainly fine-grained storm depositsfilling two storm-cut gutter casts (Figs. 3, 5.3, 5.6). Some of thespecimens from Farm Aar are aligned parallel with each other(Fig. 4.3), but most show no preferred orientation in a horizontalsense (Fig. 3.1, 3.4), implying that, unlike the unimodallyoriented fronds of Mistaken Point in Newfoundland (Seilacher,1999; Wood et al., 2003), these Rangea specimens were nottethered to the seafloor during their final deposition. In contrastwith the lack of orientation in a horizontal sense, there is astrong orientation in a vertical sense, with all specimensoriented convex-down, a boat-shaped orientation also typicalof other Namibian preservations of Rangea (Grazhdankin and

an element midline cast in negative relief; note the partial collapse of the specimen where the axial space fill is absent distally; a single vane is present on left,two vanes with marginal traces are preserved on right; 2, outlined dorsal surface with lines of section for 3–8, axial shaft of adjacent Rangea specimen arrowed;3, axial section A–B photographed with raking natural light; 4, outline of axial section A–B, axial shaft fill shaded dark for solid granular sediment, light shadingfor finer degraded sediment, proximal node of axial bulb bracketed; 5, lateral section C–D photographed with raking natural light showing thick region of vanepreservation along the ventral surface; 6, outline of lateral section C–D showing flattened structure of vanes 4 and 5; 7, transverse section E–F photographed withraking natural light; 8, outline of transverse section E–F with five vanes and the position of a sixth vane indicated, axial shaft fill shaded dark for solid granularsediment, light shading for finer degraded sediment. All scale bars¼1 cm. Abbreviations: ab¼axial bulb; af¼axial fill; as¼axial stalk; av¼axial volume;em¼element midline; mpb¼major primary branch; mt¼marginal tube; nab¼proximal node of axial bulb; spb¼subsidiary primary branch; v¼vane.


FIGURE 7—Rangea axial bulb and stalk morphology, Farm Aar, Channel 1: 1, lower surface of Rangea NSEMF643-b3; 2, outlined lower surface of RangeaNSEMF643-b3 showing line of axial section G–H; 3, Rangea NSEMF643-b3 thin section G–H photographed with raking natural light; 4, outline of Rangea


Seilacher, 2005) and Pteridinium (Grazhdankin and Seilacher,2002). This combination of a strong orientation in a verticalsense but little or no preferred orientation horizontally wasregarded by Grazhdankin and Seilacher (2005) as indicative ofan infaunal habit, but is also consistent with deposition oftransported, untethered specimens of Rangea during a stormevent, with the upturned edges reflecting water escaping upwardwhile sediment settled downward from suspension (Fig. 10).

Axial bulbs of Rangea from the channels are filled with fine-grained sandstone that is similar in all regards to the sandstonefill in the bottom of the gutter cast a few millimeters tocentimeters below the fossil, effectively ruling out thepossibility that this fill represents either a purely biochemicalprecipitate or a later infiltration of sand after burial. Faintlaminations parallel with the base of the axial bulb imply thatsandstone fill of the bulb occurred while the frond was in avertical orientation (Figs. 5.5, 7.4), before dislocation andsubsequent deposition in a horizontal orientation. The sandstonefill in the proximal part of the axial stalk becomes increasinglyloosely packed, porous and pyritic/jarositic distally passing intoa hollow cone which tapers to the distal end of the fossil.Sandstone fills the axial bulb and also thinly lines the axial stalk(Figs. 6.3, 6.4, 7.3, 7.4). The sand-filled axial bulb is presentlyconnected to, but stratigraphically higher than, the open stalk.Despite this orientation there is no evidence that loose sandflowed from the bulb into the stalk, nor is there any sign ofcompaction of the stalk during burial. This implies that sandfilled the axial bulb very early, either during life or immediatelyafter death, while the stalk was still filled with stiff organicmaterial preventing both the flow of the loose sand fill duringburial and collapse of the stalk during burial. It is likely that theopen stalk was then filled with an early diagenetic mineral,which preserved its form through subsequent burial compactionand mild orogenesis and was then removed in the modernweathering environment to yield the open stalk visible today.

It is tempting to conclude that sand was packed in the bottompart of Rangea during life especially since the presence of asand-filled bulb overlain by a hollow axial stalk would provideincreased stability on the seafloor, much like a child’s toy with aweighted base to keep it upright, an explanation that haspreviously been applied to some Ediacaran and Cambrian taxainterpreted as soft-bodied cnidarians (Seilacher, 1992; Savazzi,2007).

Several unrelated protistan and animalian groups in modernseas have convergently evolved the ability to incorporate sandgrains into their bodies for structural support and/or ballast, andthese may usefully serve as constructional (albeit not phyloge-netic) analogues for sand-grain incorporation in Rangea.Xenophyophores are giant, deep-sea protists that commonlyagglutinate sediment tests, presumably as structural support oftheir delicate cytoplasm. Species variously incorporate addi-tional sediment in the form of internally secreted fecal pelletsand by the selective ingestion of mineral grains from thesubstrate into the cytoplasm as an internal skeleton (Tendal,1972; Gooday et al., 2011). This process is also seen in juvenilesand dollars, which selectively ingest sand grains from the

substrate and use these as a weight-belt for increased stability inshifting substrates (Chia, 1973; Seilacher, 1979; Mooi andChen, 1996). We note further that the ‘‘Zoantharia’’ build astolon, mat or other support with sediment particles and debris(Haywick and Mueller, 1997; Reimer et al., 2010). Manysponges do the same and also attract other organisms withintheir tissues, preferably those capable of secreting calcareousskeletons (Cerrano et al., 2007; E. Savazzi, personal commun.,2012). According to this model, Rangea from Farm Aar wouldhave derived sand ballast during deposition of the fine-grainedsand in the lower part of the gutter or from similar sedimentselsewhere and lived as upright, epibenthic fronds with theirbases resting on or slightly buried in the sediment (Fig. 10.1).This interpretation implies that the rangeomorph elements nearthe base of Rangea (Fig. 9) may have had a structural as well asfood-gathering function, a view consistent with rangeomorphelements covering the bottom side of Fractofusus (Gehling andNarbonne, 2007) and surrounding the holdfast of Bradgatia(Flude and Narbonne, 2008, fig. 4) from Newfoundland.Additionally, the expansion of the marginal tubes surroundingthe proximal bulb may well have provided further support. Thepresence of sand ballast is also consistent with the concentrationof Rangea specimens in gutter casts and their extreme scarcityin otherwise indistinguishable storm beds throughout thesuccession. Specimens were likely transported and depositedhorizontally during the final storm event, producing a concave-up (boat-shaped) profile due to their settling out of a sediment-rich suspension at the end of a storm event (Fig. 10.3). Evidencefor only limited alignment of Rangea fossils supports our viewthat the fronds were untethered and implies that the waningstages of the storm were characterized by oscillatory/turbulentconditions rather than unidirectional flow. Distal vanes col-lapsed during burial, but the presence of potentially moreresistant proximal vanes and the greater thickness of the axialbulb as opposed to the axial stalk likely resulted in flexure androtation of this bulb during burial to produce the fossil formpreserved today (Fig. 10.6, 10.7).

Other interpretations of the life habit of Rangea have alsobeen proposed. An early interpretation of the Ediacaran fossilsfrom Namibia as ‘‘polyps with a float structure for buoyancy inthe water column’’ (Brasier, 1979) is consistent with ourreconstruction (Fig. 9) but is not consistent with the taphonomyof the fossils, especially the ubiquitous presence of a sandstone-filled axial bulb. Interpretation of Rangea as a sessile infaunalorganism (Grazhdankin and Seilacher, 2005) was invoked toexplain the consistent boat-shaped (convex-down) relief ofRangea and Pteridinium in the absence of evidence for any axialor basal supporting structure for an epibenthic life style. Theadditional morphological attributes revealed by these newspecimens and the restriction of Rangea to preservation withinsediments deposited during the waning phases of storms do notsupport this interpretation. Because all Rangea preservations todate represent transported organisms, evidence for sedimentdisplacement during growth has not been found or can beexpected from these deposits. Modeling implying that the self-similar (rangeomorph) architecture of Rangea was specifically

NSEMF643-b3 thin section G–H; 5, excavated axial bulb F640-b, upper, profile and lower view, top to bottom, respectively; 6, upper view of NESMF636-f withaxial node arrowed, profile view of NESMF636-f with deposition fragment NESMF636-e attached at position of arrow, lower view of NESM F636-f, top tobottom, respectively; 7, partially excavated axial bulb NESMF641-e, upper, profile and lower view, top to bottom, respectively. All scale bars¼1 cm.Abbreviations: ab¼axial bulb; af¼axial fill; as¼axial stalk; av¼axial volume; em¼element midline; mpb¼major primary branch; mt¼marginal tube; nab¼proximalnode of axial bulb; spb¼subsidiary primary branch; v¼vane.


adapted for extracting nutrients from the water column

(Laflamme et al., 2009) makes interpretation of Rangea as an

infaunal organism even more unlikely. While neither pelagic nor

infaunal models for Rangea can be strictly ruled out, the new

specimens from Farm Aar are most consistent with the

traditional interpretation of Rangea as an epibenthic frond

(Jenkins, 1985), with the significant proviso that no holdfast is

preserved which might have tethered Rangea to the bottom

during life. Our view that Rangea was an untethered epibenthic

frond further implies that virtually all Rangea are likely to have

been transported at least a short distance before their final burial

during the waning stages of storm activity.

CONCLUSIONS

Rangea was the first complex Ediacaran fossil described

anywhere in the world (Gurich, 1930, 1933), and over the

subsequent 80 years its reconstruction has been analyzed by

some of the key workers in Ediacaran paleontology. All of these

workers made important discoveries that elucidated critical

aspects of the complex architecture and construction that

characterize Rangea. Pflug (1970) first recognized its highly

multifoliate nature and the constraints this placed on Rangea

reconstructions. Germs (1973) described the flexibility of the

Rangea vanes in life, and Jenkins (1985) described features that

permitted reconstruction as an epibenthic frond. Dzik (2002)

FIGURE 8—Rangea axial bulb, marginal tube morphology and symmetry, Farm Aar: 1, Rangea NESM F635-c lower (ventral) view, scale bar¼1 cm; 2, RangeaNESMF635-c, upper (dorsal) view, scale bar¼1 cm; 3, outline of Rangea NESMF635-c in dorsal view showing proximal preservation of marginal tracesrepresented as translucent white, superimposed on a flipped outline of the lower view shaded mid-gray with axial region shaded dark gray, scale bar¼1 cm; 4,diagrammatic transverse section at axial bulb of Rangea showing architecture and symmetry postulated from major confined regions of sediment fill (stippled)and major traces of jarosite (black lines); 5, diagrammatic proximal view of Rangea architecture and symmetry postulated from molded surfaces of marginaltubes and axial bulb.


recognized an axial region within Rangea, and Grazhdankin andSeilacher (2005) recognized the alternate major and minorbranching that constitutes the external surface of the Rangeapetalodium. The major contribution of this study may be theelucidation of the morphology and significance of the hexaradialaxial bulb and axial stalk over which the six vanes of frondoseelements of Rangea were draped. This is not the end of theanalyses, and new discoveries and new techniques will continueto yield exciting insights into this iconic Ediacaran taxon.

ACKNOWLEDGMENTS

Many people over the years have helped us bring this researchpaper to fruition: staff at the Geological Survey of Namibia,especially K. Mhopjeni, H. Mocke, U. Schrieber and E. Grobler;owners of Farm Aar, B. Boehm-Erni and the late B. Boehm, alongwith N. Kloster; E. Ndalibobule of the National Heritage Councilof Namiba; Transworld Cargo; U. Linnemann and M. Hofmann(Senckenberg Naturhistorische Sammlungen, Museum fur Min-eralogie and Geology) in Dresden for radiometric dating; J.Kaufmann (Geology Department, University of Maryland) forgeochemical analyses; R. W. Dalrymple for sedimentologicalassessment; G. Holm and R. Douglass for rock preparation; G.Hutchinson for microprobe analysis; H. Jamieson and R. Petersonfor geochemical input; E. Savazzi for advice on functional

morphology; S. Morton for photography; P. Komarower foreditorial assistance; D. Gelt for drafting; R. Trusler and M.Anderson for IT assistance with graphics; M. A. Zakrevskaya(Paleontological Institute, RAS) for Russian translation; and C.Williams, along with students N. Fournie, C. Wemmers, O.Trusler and M. Meyers for field and laboratory assistance. Thanksto the Hoffmann family and Hotel Christophe for accommodationover many years; the National Geographic Society and theInternational Geosciences Program (IGCP) of UNESCO forgrants supporting the field work that led to the discovery of theRangea specimens, as did the Natural Sciences and EngineeringResearch Council of Canada (NSERC) and Queen’s University.Material was collected under permits from the National HeritageCouncil of Namibia: Permit 4 of 2004, 11 of 2006, 18 of 2008, 13of 2009 and 6 of 2011, and resides in the Geological Survey ofNamibia, Ministry of Mines and Energy collections in Windhoek.Thanks to our families for listening to our endless debates, inparticular G. Trusler and T. Rich.

REFERENCES

ABELSON, J., J. M. METZ, N. MCLOUGHLIN, P. A. COHEN, AND M. M. TICE. 2012.Deep water incised valley deposits at the Proterozoic–Cambrian boundaryin southern Namibia contain abundant Treptichnus pedum. Palaios, 27:252–273.

BLADH, K. W. 1982. The formation of goethite, jarosite, and alunite during theweathering of sulfide-bearing felsic rocks. Economic Geology, 77:176–184.

BOUOUGRI, E. H., H. PORADA, K. WEBER, AND J. REITNER. 2011. Sedimentologyand palaeoecology of Ernietta-bearing Ediacaran deposits in southernNamibia: implications for infaunal vendobiont communities. Advances inStromatolite Geobiology. Lecture notes in Earth Sciences, 313:473–506.

BRASIER, M. D. 1979. The Cambrian radiation event, p. 103–159. In M. R.House (ed.), The Origin of Major Invertebrate Groups. SystematicsAssociation Special Volume No. 12. Academic Press, London.

BRASIER, M. D. AND J. ANTCLIFFE. 2004. Decoding the Ediacaran enigma.Science, 305:1115–1117.

BRASIER, M. D. AND J. ANTCLIFFE. 2009. Evolutionary relationships within theAvalonian Ediacara biota: new insights from laser analysis. Journal of theGeological Society, London, 166:363–384.

CERRANO, C., B. CALCINAI, C. GIOIA DE CAMILLO, L. VALISANO, AND G.BAVESTRELLO. 2007. How and why do sponges incorporate foreign material?Strategies in Porifera, p. 239–246. In M. R. Custodio, G. Lobo-Hajdu, E.Hajdu, and G. Muricy (eds.), Porifera Research: Biodiversity, Innovationand Sustainability. Serie Livros 28. Museu Nacional, Rio de Janeiro.

CHIA, F. S. 1973. Sand dollar: a weight belt for the juvenile. Science, 181:73–74.

DZIK, J. 2002. Possible ctenophoran affinities of the Precambrian ‘‘sea-pen’’Rangea. Journal of Morphology, 252:315–334.

ELLIOTT, D. A., P. VICKERS-RICH, P. W. TRUSLER, AND M. HALL. 2011. Newevidence on the taphonomic context of the Ediacaran Pteridinium. ActaPalaeontologica Polonica, 56:641–650.

ERWIN, D. H., M. LAFLAMME, S. M. TWEEDT, E. A. SPERLING, D. PISANI, AND K.J. PETERSON. 2011. The Cambrian conundrum: early divergence and laterecological success in the early history of animals. Science, 334:1091–1097.

FLUDE, L. I. AND G. M. NARBONNE. 2008. Taphonomy and ontogeny of amultibranched Ediacaran fossil: Bradgatia from the Avalon Peninsula ofNewfoundland. Canadian Journal of Earth Sciences, 45:1095–1109.

GEHLING, J. G. 1991. The case for Ediacaran roots to a metazoan tree.Geological Society of India Memoir, 20:181–224.

GEHLING, J. G. 1999. Microbial mats in terminal Neoproterozoic siliciclastics:Ediacaran death masks. Palaios, 14:40–57.

GEHLING, J. G. AND G. M. NARBONNE. 2007. Spindle-shaped fossils from theMistaken Point assemblage, Avalon Zone, Newfoundland. CanadianJournal of Earth Sciences, 44:367–387.

GERMS, G. J. B. 1972. The stratigraphy and palaeontology of the lower NamaGroup, South West Africa. Precambrian Research Unit, University of CapeTown, Bulletin 12, 1–250.

GERMS, G. J. B. 1973. A reinterpretation of Rangea schneiderhoehni and thediscovery of a related new fossil from the Nama Group, South West Africa.Lethaia, 6:1–9.

GERMS, G. J. B. 1983. Implications of a sedimentary facies and depositionalanalysis of the Nama Group in South West Africa, Namibia. GeologicalSociety of South Africa, Special Publication, 11:89–114.

GOODAY, A. J., A. ARANDA DA SILVA, AND J. PAWLOWSKI 2011. Xenophyophores(Rhizaria, Foraminifera) from the Nazare’Canyon (Portuguese margin, NEAtlantic). Deep Sea Reasearch II, 58:2401–2419.

FIGURE 9—Hypothetical life reconstruction of Rangea shown partly cutaway to reveal the architecture of the body form as deduced from thepreservation on specimens from Farm Aar, Namibia.


FIGURE 10—Taphonomic scenario of the Rangea accumulations on Farm Aar, Namibia: 1, living Rangea community; 2, storm-dislodged Rangea transportedby suspension in a sediment-water mixture flow; 3, burial of Rangea in erosion gutter during waning stages of storm, arrows indicate slowing flow andcommencement of sediment fall from suspension; 4, sediment and Rangea fall from suspension, (specimens shown sectioned), arrows indicating sediment fall


GRAZHDANKIN, D. V. 2004. Patterns of distribution in the Ediacaran biotas:facies versus biogeography and evolution. Paleobiology, 30:203–221.

GRAZHDANKIN, D. V. AND A. SEILACHER. 2002. Underground Vendobionta fromNamibia. Palaeontology, 45:57–78.

GRAZHDANKIN, D. V. AND A. SEILACHER. 2005. A re-examination of the Nama-type Vendian organism Rangea schneiderhoehni. Geological Magazine,142:571–582.

GROTZINGER, J. P., S. A. BOWRING, B. Z. SAYLOR, AND A. J. KAUFMAN. 1995.Biostratigraphic and geochronologic constraints on early animal evolution.Science, 270:598.

GROTZINGER, J. P. AND R. MILLER. 2008. The Nama Group, p. 13.229–13.272.In R. Miller (ed.), The Geology of Namibia. Geological Society of NamibiaSpecial Publication, 2.

GURICH, G. 1930. Die bislang altesten Spuren von Organismen in Sudafrika.International Geological Congress (XV), Pretoria, Union of South Africa,Die altesten Fossilien Sud-Afrikas, 2:670–680.

GURICH, G. 1933. Die Kuibis-Fossilien der Nama-Formation von Sudwest-afrika. Palaontologische Zeitschrift, 15:137–154.

HAYWICK, D. W. AND E. M. MUELLER. 1997. Sediment retention in encrustingPalythoa sp.—a biological twist to a geological process. Coral Reefs, 16:39–46.

JAMBOR, J. L. AND D. W. BLOWES. 1998. Theory and applications of mineralogyin environmental studies of sulfide-bearing mine wastes, p. 367–401. In L.J. Cabri and D. J. Vaughan (eds.), Modern Approaches to Ore andEnvironmental Mineralogy, 27. Mineralogical Association of Canada ShortCourse Series, Mineralogical Association of Canada, Ottawa, Canada.

JENKINS, R. J. F. 1985. The enigmatic Ediacaran (Late Precambrian) genusRangea and related forms. Paleobiology, 11:336–355.

LAFLAMME, M. AND G. M. NARBONNE. 2008a. Ediacaran fronds. Palae-ogeography, Palaeoclimatology, Palaeoecology, 258:162–179.

LAFLAMME, M. AND G. M. NARBONNE. 2008b. Competition in a Precambrianworld: palaeoecology of Ediacaran fronds. Geology Today, 24:182–187.

LAFLAMME, M., S. XIAO, AND M. KOWALEWSKI. 2009. Osmotrophy in modularEdiacaran organisms. Proceedings of the National Academy of Sciences ofU.S.A., 106:14438–14443.

LOTTERMOSER, B. G. 2010. Mine Wastes: Characterization, Treatment andEnvironmental Impacts (third edition). Springer-Verlag, Berlin, Germany,400 p.

MOOI, R. AND C. P. CHEN. 1996. Weight belts, diverticula, and the phylogenyof the sand dollars. Bulletin of Marine Science, 58:186–195.

MYROW, P. M. 1992. Pot and gutter casts from the Chapel Island Formation,southeast Newfoundland. Journal of Sedimentary Research, 62:992–1007.

MYROW, P. M. AND J. B. SOUTHARD. 1996. Tempestite deposition. Journal ofSedimentary Research, 66:875–887.

NARBONNE, G. M. 2004. Modular construction of early Ediacaran complex lifeforms. Science, 305:1141–1144.

NARBONNE, G. M., B. Z. SAYLOR, AND J. P. GROTZINGER. 1997. The youngestEdiacaran fossils from southern Africa. Journal of Paleontology, 71:953–969.

NARBONNE, G. M., M. LAFLAMME, C. GREENTREE, AND P. TRUSLER. 2009.Reconstructing a lost world: Ediacaran rangeomorphs from Spaniard’s Bay,Newfoundland. Journal of Paleontology, 83:503–523.

NARBONNE, G.M., S. XIAO, AND G. SHIELDS. 2012. The Ediacaran Period, p.427–449. In F. Gradstein, J. Ogg, M. D. Schmitz, and G. Ogg (eds),Geologic Timescale 2012. Elsevier, Boston.

PFLUG, H. D. 1970. Zur fauna der Nama-Schichten in Sudwest-Afrika; II.Rangeidae, Bau und systematische Zugehorigkeit. PalaeontographicaAbteilung A, 135:198–231.

PFLUG, H. D. 1972. Systematik der jung-prakambrischen Petalonamae.Palaontologische Zeitschrift, 46:56–67.

PLINT, A. G. 2010. Wave- and storm-dominated shoreline and shallow-marinesystems, p. 167–199. In N. P. James and R. W. Dalrymple (eds.), FaciesModels 4. Geological Association of Canada.

REIMER, J. D., S. NAKACHI, M. HIROSE, AND H. SHINJI. 2010. Using hydrofluoricacid for morphological investigations of Zoanthids (Cnidaria: Anthozoa): acritical assessment of methodology and necessity. Marine Biotechnology,12:605–617.

RICHTER, R. 1955. Die altesten Fossilien Sud-Afrikas. SenckenbergianaLethaea, 36:243–289.

SAVAZZI, E. 2007. A new reconstruction of Protolyellia (Early Cambrianpsammocoral), p. 339–353. In P. Vickers-Rich and P. Komarower (eds.),The Rise and Fall of the Ediacaran Biota. Geological Society of LondonSpecial Publication 286.

SAYLOR, B. Z., J. P. GROTZINGER, AND G. J. B. GERMS. 1995. Sequencestratigraphy and sedimentology of the Neoproterozoic Kuibis andSchwarzrand subgroups (Nama Group), southwestern Namibia. Precambri-an Research, 73:153–172.

SAYLOR, B. Z., A. J. KAUFMAN, J. P. GROTZINGER, AND F. URBAN. 1998. Acomposite reference section for terminal Proterozoic strata of southernNamibia. Journal of Sedimentary Research, 68:1223–1235.

SAYLOR, B. Z., J. M. POLING, AND W. D. HUFF. 2005. Stratigraphic and chemicalcorrelation of volcanic ash beds in the terminal Proterozoic Nama Group,Namibia. Geological Magazine, 142:519–538.

SCHMITZ, M. D. 2012. Appendix 2—Radiometric ages used in GTS2012, p.1045–1082. In F. Gradstein, J. Ogg, M. D. Schmitz, and G. Ogg (eds.), TheGeologic Time Scale 2012. Elsevier, Boston.

SEILACHER, A. 1979. Constructional morphology of sand dollars. Paleobiology,5:191–221.

SEILACHER, A. 1992. Vendobionta and Psammocorallia: lost constructions ofPrecambrian evolution. The Journal of the Geological Society of London,149:607–614.

SEILACHER, A. 1999. Biomat-related lifestyles in the Precambrian. Palaios, 14:86–93.

SEILACHER, A. 2007. The nature of Vendobionts. Geological Society ofLondon, Special Publication 286(1):387–397.

TENDAL, O. S. 1972. A monography of the Xenophyophoria (Rhizopodea,Protozoa). Galathea Report, 12:7–99.

VICKERS-RICH, P. 2007. The Nama fauna of southern Africa, p. 69–88. In M. A.Fedonkin, J. G. Gehling, K. Grey, G. M. Narbonne, and P. Vickers-Rich(eds.), The Rise of Animals: Evolution and Diversification of the KingdomAnimalia. Johns Hopkins University Press.

WOOD, D. A., R. W. DALRYMPLE, G. M. NARBONNE, J. G. GEHLING, AND M. E.CLAPHAM. 2003. Paleoenvironmental analysis of the late NeoproterozoicMistaken Point and Trepassey formations, southeastern Newfoundland.Canadian Journal of Earth Sciences, 40:1375–1391.

XIAO, S. AND M. LAFLAMME. 2009. On the eve of animal radiation: phylogeny,ecology and evolution of the Ediacara biota. Trends in Ecology andEvolution, 24:31–40.

ACCEPTED 20 SEPTEMBER 2012

and water expulsion; 5, detail, sediment sorting during settling and compaction, Rangea specimens begin to decay and deform, with early diagenetic pyritecoating or replacing the Rangea biomaterials, arrows indicate sediment compaction and water expulsion; 6, detail, sediment fully compacted and lithified, pyritebiofilms altering to jarosite, arrows indicate compaction pressure; 7, detail, molded surfaces of Rangea at the same stratigraphic level revealed in part andcounterpart relief, arrows indicate forced parting.


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Jurnal of o Paleontology - Monash University · Body mass estimations and paleobiological inferences on a new species of large Caracara (Aves, Falconidae) from the late Pleistocene