Geot Mag 126 (2) 1989 pp 177-86 Printed in Great Britain 111

A new genus of brissid echinoid from the Miocene ofAustralia

K J M c N A M A R A amp C A H Y E E f

Department of Palaeontology Western Australian Museum Francis Street Perth Western Australia 6000 Australiaf20 Bayley Street Hamilton Victoria 3300 Australia

(Received 9 September 1987 revised version received 20 September 1988 accepted 22 September 1988)

Abstract - The brissid echinoid Amoraster (gen nov) is described from Miocene strata in southernAustralia on the basis of two species A paucituberculata sp nov which ranges from theBatesfordian (latest Early Miocene) Bochara Limestone to the Baimsdalian-Mitchellian (Middle-Late Miocene) Port Campbell Limestone in Victoria and A tuberculata sp nov from theLongfordian (Early Miocene) Mannum Formation in South Australia Morphological changes whichoccurred with the evolution of A paucituberculata from A tuberculata are interpreted as beingadaptations to the occupation of a finer grained sediment by the descendant species

1 Introduction

It is now more than 120 years since the first brissidechinoid species was described from the Tertiarydeposits of southern Australia (Tenison Woods1867) Since that time 16 further species placed ineight genera have been described (Kruse amp Philip1985 McNamara Philip amp Kruse 1986) Brissidechinoids form the major part of the rich AustralianTertiary spatangoid fauna comprising 44 of generaand 38 of species

It is therefore a little surprising that our collectingin recent years has yielded a further two undescribedbrissid species which cannot be accommodated withinany known living or fossil echinoid genus Even moresurprising perhaps is that one of the species shouldhave been collected from the cliffs of the MurrayRiver near Mannum in South Australia one of themost well-known fossil collecting sites in AustraliaFurthermore this undescribed genus is particularlylarge being exceeded in size amongst AustralianTertiary echinoids only by Victoriaster (one of thelargest echinoids ever to have lived) and some of thelarger species of Pericosmus (McNamara amp Philip1984)

The aim of this paper therefore is to describe thetwo new species and the new genus into which they areplaced In addition the morphological evolutionwhich occurred between the two species is analysedand the functional significance of these changes isassessed

Measurements on the specimens were made with avernier calliper to an accuracy of 01 mm A numberof parameters are expressed as percentages of maxi-mum test length (TL) The labrum index is ameasure of maximum lengthmaximum anteriorwidth Specimens are housed in the collections of theWestern Australian Museum (WAM)

One new term bifastigiate is introduced Thisrefers to the presence of two raised points on theplastronal keel

2 Stratigraphy

The earliest occurrence of the new genus is in theMannum Formation which is Longfordian (EarlyMiocene) in age (Lindsay 1985) This is a sequence ofyellow bioclastic calcarenites which transgresses ontobedrock on the western margin of the Murray Basin inSouth Australia The Mannum Formation is exposedas cliff sections about 15 m thick on the banks of theMurray River in the Mannum region (Fig 1) In totalthe formation is about 45 m thick It is a veryfossiliferous unit being dominated by echinoidsprincipally Lovenia forbesi (Tenison Woods) Eupa-tagus murrayensis (Laube) and E wrighti (Laube)

A single specimen of the new genus is known fromthe Batesfordian (latest Early Miocene) BocharaLimestone in the Otway Basin at Muddy CreekVictoria This is a porous yellow-brown beddedbryozoal calcarenite attaining a maximum thicknessof 23 m (Spencer-Jones 1971) The Bochara Lime-stone is considered to have been deposited in arelatively shallow high-energy environment (Abeleet al 1976) and is likely to represent a marginalequivalent of the Port Campbell Limestone

The new genus has also been collected from thePort Campbell Limestone at Portland Victoria (Fig1) Here the unit is a relatively fine-grained foramini-feral calcarenite thought to have accumulated off-shore in deeper water than the Bochara Limestone(Abele et al 1976) The Port Campbell Limestone is athick unit in excess of 150 m (Baker 1950) In thePort Campbell Embayment it is Bairnsdalian (MiddleMiocene) in age (Ludbrook 1973) although theupper part of the formation at Portland may be a little

12-2

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

178 K J MCNAMARA amp C AH YEE

w2

uOtmdash

S

bull4-gt

V

T3

Mitchellian

Baimsdalian

BalcombianBatcsfordian

Longfordian

A paucituberculata

IA tuberculata

Figure 1 Geographical and stratigraphical distribution ofAmoraster in southern Australia

younger representing the upper part of foraminiferalzone N16 and the basal part of zone 17 (SingletonMcDougall amp Mallett 1976) This would place it inthe Late Miocene Mitchellian stage

3 Systematic descriptions

Order SPATANGOIDA Claus 1876Family BRISSIDAE Gray 1855

Genus Amoraster nov

Diagnosis Test inflated apex coincident with oranterior of apical system primary tuberculationabsent or weakly developed and confined to theposterior plate series in each of the paired inter-ambulacra petals sunken and poriferous zones deeplyincised pore pairs in petals deeply conjugate ambu-

lacrum III sunken adapically labrum short widerthan long periproct wider than long and plastronalkeel bifastigiate

Derivation of name From the Greek amora a cakealluding to the shape of the test and aster a star

Type species Amoraster paucituberculata sp nov

Age and distribution From the Early to Late Miocene(Longfordian to Mitchellian) of the Murray andOtway Basins in southern Australia

Remarks While a number of brissid genera may sharethe same morphological character each can bedistinguished from all others by its unique combina-tion of characters Thus although Amoraster can notbe distinguished from other brissids on the basis ofany one major characteristic feature a unique com-bination of morphological features which character-izes the two species placed in Amoraster militateagainst their emplacement within any known genusAlthough it might be argued that the superficialsimilarity which the species bear to species ofEupatagus indicates that they could be placed withinthat genus such a course of action would mean awholescale extension of the generic concept ofEupatagus Moreover it would result in many othercurrently established brissid genera being synony-mized into Eupatagus All this would achieve is a falsepicture of the true extent of brissid generic diversityduring Tertiary time

A further argument for the establishment of a newgenus is the fact that two species have been recognizedas forming part of a single lineage evolving in parallelwith a plexus of Eupatagus species (Kruse amp Philip1985) These Oligocene to Miocene southern Austral-ian species cover almost the entire spectrum ofmorphotypes currently regarded as belonging withinEupatagus Thus they are most appropriate forcomparing with the two species described herein andfor highlighting the fact that these two species lie welloutside of the range of the generic concept ofEupatagus

Amoraster differs in many important respects fromEupatagus (Table 1) Whereas primary tubercles inEupatagus are always present within the aboral areabounded by the peripetalous fasciole in Amorasterthey may be absent or if present they are confined tothe posterior series of plates in the paired inter-ambulacra that is plates 1 a 2a 3 b and 4b Amorastercan further be distinguished from Eupatagus by theshape of the test In Eupatagus the apex of the test isposterior of the apical system whereas in Amoraster itis either coincident with or anterior to it Amorasterfurther differs from Eupatagus in having sunkenpetals slightly indented peripetalous fasciole shorterlabrum (Table 1) and a periproct which is transverselyoval rather than dorso-ventrally elongate (see Fig 5)The plastron shows an important difference in that theposterior keel is bifastigiate

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

New Miocene echinoid genus

Table 1 Distinguishing morphological features of Amoraster and the four genera with which it is most similar

179

Features

Test height

Oral surface

Paired ambs

Pore zones

Frontal amb

Peripetalous fasciole

Labrum

Plastron

Pcriproct

Primary tubercles

Amoraster

High arched

Sunken to peristome

Closed amp sunken

Deeply incised

Sunken adapically

Slightly indented betweenpetals

Short-index 075-09

Bifastigiate keel and notparallel-sided

Wider than long

Absent or if presentrestricted to la 2a 3b4b

Eupatagus1

Low arched

Flat

Closed amp notsunken

Weakly incised

Not sunken

Not indentedbetween petals

Long-index 15-3

Keeled and notparallel-sided

Longer than wide

Present in 1 ab2ab 3ab 4ab

Granobrissoides1

Low arched

Slightly sunken toperistome

Closed amp notsunken

Weakly incised

Not sunken

Not indentedbetween petals

Short-index 1

Keeled and parallel-sided

Longer than wide

Absent

Gillechimis

Low arched

Flat

Open amp si sunken

Not incised

Sunken

Not indentedbetween petals

Long-index 2-25

Keeled and notparallel-sided

Longer than wide

Present in la 2a3b 4b

Lajanaster3

Low arched

Flat

Closed amp si sunken

Weakly incised

Sunken adapically

Unknown

Unknown

Very narrow

Circular

Present in 1 a 2a3b 4b

1 Data from Mortensen (1951) and Kruse amp Philip (1985)2 Data from McNamara Philip amp Kruse (1986)3 Data from Kier (1984)

Another endemic Australian brissid with whichAmoraster shows some similarities is GranobrissoidesThis Late Oligocene genus has a similar petalconfiguration to Amoraster and also lacks primarytubercles (McNamara Philip amp Kruse 1986) Amor-aster can be distinguished however by its muchlarger size anterior apex more parallel-sided sunkenpetals wider periproct and broader bifastigiateplastron which unlike Granobrissoides is not parallel-sided

The only other Australian Tertiary brissid echinoidto have primary tubercles confined to the posteriorplate series in paired aboral interambulacra is Gillech-inus Amoraster differs however in having closedpetals with deeply incised pore zones shorter labrum(Table 1) bifastigiate keel and wider periproct

Of brissid genera which do not occur in AustraliaAmoraster most closely resembles the Miocene Cubangenus Lajanaster (Kier 1984) Both have lanceolatepetals no anterior notch and few primary tuberclesconfined to the posterior interambulacral plates seriesHowever Amoraster can be distinguished by its moretumid test more deeply conjugate pore pairs moreflexuous anterior petals which are equal to or longerthan the posterior the more anteriorly prominentlabrum and much broader plastron (Table 1)

Amoraster paucituberculata sp novFigures 2-4

Diagnosis Test tumid and strongly vaulted primarytubercles absent or very rare petals slightly sunkenanterior longer than posterior interporiferous zonesswollen periproct moderately sunken and labrumstrongly anteriorly elongate

Derivation of name Alluding to the paucity of primarytubercles

Type material Holotype WAM 87303 from theMiddle-Late Miocene (Bairnsdalian-Mitchellian)Port Campbell Limestone Portland Victoria Para-types WAM 851271 87522 87523 from the PortCampbell Limestone in coastal cliffs 35 m aboveground level below the lighthouse Portland VictoriaWAM 851356 from same locality and formation as851271 but from a higher level at the top of the cliffimmediately below the lighthouse possibly Mitchel-lian (Late Miocene) in age WAM 87304 from thesame locality and horizon as the holotype WAM86293 from the latest Early Miocene (Balcombian)Bochara Limestone Muddy Creek 400 m down-stream from wooden bridge near old Yulecart bore

Description Test large reaching a maximum knownlength of 117 mm slightly narrower than longmaximum width posterior of centre 97 TL apexhigh 68 TL confluent with or anterior of apicalsystem anterior surface of test strongly declinedposterior surface moderately steeply declined (Fig4d) No anterior notch present Apical system anteriorof centre 35 TL from anterior ambitus ethmolyticwith four genital pores madreporite extending poster-iorly by more than half length of apical system (Figs3a 4e) Ambulacrum III flush with test surfaceadambitally but adapically is slightly depressedbears an unknown number of minute isopores Petalsslightly depressed slightly flexed distally with deeplyconjugate pore pairs and swollen interporal zone (Fig2a) which is half as wide again as the pore pairs upto 24 large pore pairs in each row and about eightvery small pairs adapically Anterior pair longer thanposterior being 36-38 TL compared with 28-30TL 9 TL wide diverge at 135deg distally open

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

180 K J MCNAMARA amp C AH YEE

Figure 2 Amoraster paucituberculata sp nov Holotype WAM 87303 from the Middle-Late Miocene (Bairnsdalian-Mitchellian) Port Campbell Limestone Portland Victoria (a) aboral view (b) adoral view Both x 1

Posterior petals diverge at 55deg 7 TL wide distallyclosed Peripetalous fasciole slightly re-entrant be-tween petals particularly between anterior pair andambulacrum III Posterior half of each posterior

series of paired interambulacral plates inclined alongmargins of petals Rarely these areas bear one or twotubercles per plate (Fig 2 a) Margins of inter-ambulacra 2 b and 3 a adjacent to ambulacrum III

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

New Miocene echinoid genus 181

1mm

5 mmFigure 3 Plating drawings of Amoraster paucituberculata(a) apical system (WAM 86293) (b) adoral surface (WAM87522)

may bear irregular scatterings of tubercles slightlylarger than general covering of secondary tubercles

Adoral surface gently convex Peristome slightlysunken anterior margin located 26-28 TL fromanterior ambitus relatively small width 13-16 TLLabrum projects almost halfway across peristome inlarge specimens but less so in small ones (Figs 2 b3 b) posteriorly narrows abruptly then broadensbefore constricting to half this width where it abuttsthe plastron Phyllode with 12 unipores in ambulacraII and IV eight in III and five in I and V Plastronsmall width 25 TL with weakly bifastigiate keel(Fig 4 b) Subanal fasciole broad elliptical width

36 TL enclosing five pore pairs in both ambulacraI and V (Fig 4c) Periproct slightly sunken widerthan long (Figs 4c 5)

Remarks With the size of specimens ranging onlybetween 66 and 117 mm there is little opportunity toassess the extent of ontogenetic variation in thespecies However even over this size range there is asmall degree of apparent morphological change Inthe smallest known specimens the petals appearslightly more sunken than in larger individuals Thisin part is a function of the interporiferous zones beingmore swollen in the larger specimens The proportionsof large to small pore pairs in the petals increasesduring growth of the test while the petal length alsoincreases slightly Adorally the labrum projects alittle further across the peristome in larger individuals(Figs 2 b 4 b)

Amoraster paucituberculata is a relatively long-ranging species ranging from latest Early Miocenethrough to Late Miocene time The oldest specimen ofA paucituberculata shows minor differences from theyounger specimens There is no trace whatsoever ofprimary tubercles in the older form and the inter-poriferous zone in the petals is a little less swollen Inall other respects the two forms are identical Apaucituberculata is coeval with the superficially similarE rotundus Duncan in the Bochara Limestone butcan readily be distinguished by its anteriorly vaultedtest much weaker primary tuberculation moresunken and flexed petals broader subanal fasciolemore anteriorly projecting labrum and laterallyelongate periproct

Amoraster tuberculata sp novFigure 6

Diagnosis Primary tubercles present in posterior plateseries of paired interambulacra petals of similarlength peristome slightly sunken labrum only slightlyanteriorly projecting plastron with prominent bi-fastigiate keel periproct not sunken

Derivation of name Alluding to the presence ofprimary tubercles

Type material Holotype WAM 87116 from theEarly Miocene (Longfordian) Mannum Formationcliffs on Ponde Road on east side of the MurrayRiver 25 km from the Mannum Ferry SouthAustralia Paratypes WAM 86322 b d-g from samehorizon and locality as holotype

Description Test reaching a maximum known lengthof 84 mm slightly narrower than long maximumwidth at about mid-test length 93-100 TL maxi-mum height 54 TL apex anterior of apical system(Fig 6b) anterior surface steeply declined posteriorof apical system gently declined posteriorly truncateNo anterior notch present Apical system anterior of

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

182 K J MCNAMARA amp C AH YEE

Figure 4 Amoraster paucituberculata sp nov aboral (a) adoral (b) posterior (c) and lateral (d) views of paratype WAM87304 from the Middle-Late Miocene (Bairnsdalian-Mitchellian) Port Campbell Limestone Portland Victoria (e) aboralview of WAM 86293 from the Early Miocene (Batesfordian) Bochara Limestone Muddy Creek Victoria All x 1

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

New Miocene echinoid genus 183

6 7 8 9periproct width (mm)

10

Figure 5 Plot of periproct length against width forEupatagus rotundus (circles) Amoraster tuberculata (square)and Amoraster paucituberculata (triangles)

centre 33 TL from anterior ambitus AmbulacrumIII flush with test adambitally but slightly depressedadapically bearing about 15 unipores Anterior petalsslightly depressed and slightly flexed 35 TL longbearing about 22 large deeply conjugate pore pairsand about 6-8 pore pairs adapically anteriorlydivergent at 150deg interporiferous zone slightly swol-len Posterior petals almost as long as anterior pair(Fig 6a) being 33 TL long posteriorly divergent at40deg bearing a similar number of pore pairs as anteriorpair Peripetalous fasciole follows same course as thatin the type species Bevelled posterior plate series inthe paired interambulacra bear a scattering of rela-tively small primary tubercles (Fig 6 a) In inter-ambulacra 2 a and 3 b there are up to about 10 in eachin la and 4b there are about 25 These tend to bearranged in regular rows running parallel to the longaxes of the coronal plates

Adoral surface flat apart from presence of promi-nent bifastigiate keel in posterior plastron (Fig 6 c)Peristome barely sunken anterior margin located28 TL from anterior ambitus relatively smallwidth 15 TL Labrum projects only slightly acrossperistome posteriorly narrows abruptly to two-thirdsanterior width then progressively undergoes a slightnarrowing posteriorly Phyllode with eight unipores inambulacra II and IV six in III and five in I and VPlastron relatively small maximum width 30 TLSubanal fasciole broad elliptical width 36 TLenclosing five pore pairs in both ambulacra I and V(Fig 6d) Periproct not sunken wider than long(Fig 5)

Remarks Amoraster tuberculata can be distinguishedfrom its presumed descendant A paucituberculata by

its lower test its petals of more equal length theanterior pair of which are more divergent the posteriorless divergent the more tuberculate interambulacralareas between the apical system and peripetalousfasciole the flatter adoral surface less anteriorlyprojecting labrum more prominent plastronal keeland periproct which is not sunken

Like the Balcombian form of A paucituberculataA tuberculata occurs with the long-ranging Eupatagusrotundus While both species possess aboral primarytubercles they are smaller more densely concen-trated and are restricted to the posterior plate series ofthe paired interambulacra in A tuberculata Thisspecies can further be distinguished from E rotundusby the more anteriorly situated apex of the test themore deeply conjugate pore pairs in the petals whichare sunken its shorter wider peristome shorterlabrum bifastigiate plastronal keel wider subanalfasciole and transverse periproct

4 Functional significance of the morphologicalevolution of Amoraster

The origins of Amoraster lie most probably withEupatagus Like the endemic Granobrissoides whichalso evolved from Eupatagus but in Late Oligocenetime (McNamara Philip amp Kruse 1986) the MioceneAmoraster shows a reduction in aboral tuberculationas one of its diagnostic characters Even withinEupatagus itself some species such as E collabusKruse amp Philip 1985 show this trend However itshould be noted that even in such species of Eupatagusimpoverished in primary tubercles tuberculationstill occurs in eight interambulacral columns whereasin Amoraster it is restricted to four

A number of Caenozoic brissids and loveniidspossess large primary aboral tubercles supportingprominent spines (see McNamara 1982 fig 10E)Their role was almost certainly one of defence Thishas been demonstrated in Miocene species of Loveniafrom southern Australia (McNamara in prep) wheregastropod predation occurred on all parts of the testexcept in the tuberculated areas and in the regionimmediately posterior which would have been coveredby the dense array of posteriorly directed spines Thereduction and eventual loss of primary tubercles andspines in Amoraster and Granobrissoides may berelated to the occupation of deeper burrows in thesediment in a zone of reduced predation pressureLiving spinose species such as Lovenia elongata(Gray) are known to be shallow burrowers and usetheir spines in a defensive role (Ferber amp Lawrence1976) Deeply burrowing spatangoids however suchas Brissopsis Schizaster and Moira do not possesslarge primary tubercles and spines

The morphological evolution of A paucituberculatafrom A tuberculata shows some parallels with theevolutionary changes seen in a number of other

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

184 K J MCNAMARA amp C AH YEE

Figure 6 Amoraster tuberculata sp nov (a) aboral (b) lateral (c) adoral (d) posterior views of holotype WAM 87116 fromthe Early Miocene (Longfordian) Mannum Formation Mannum South Australia All x 1

echinoid lineages The most noticeable change is theincrease in height in the anterior region of the testresulting in an increase in declination of the posterioraboral surface of the test A similar increase in testheight has been documented within a number of otherechinoid lineages where it has been correlated with a

decrease in grain size of the enclosing sedimentExamples include species of Discoides from the EarlyCenomanian strata of southern England (Smith ampPaul 1985) and the southern Australian Tertiaryspatangoids Pericosmus (McNamara amp Philip 1984)and Hemiaster (McNamara 1987) Similarly species

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

New Miocene echinoid genus 185

of arachiaciid cassiduloids which have prominentlyswollen apical parts of the test also in an anteriorposition have been regarded as having inhabitedrelatively muddy sediments (Smith amp Zaghbib-Turki1985)

The similar increase in anterior test height inAmoraster can to some degree also be correlatedwith a decrease in sediment grain size A tuberculatais preserved in calcarenites which range in size from01 to 04 mm in diameter whereas A paucituberculataoccurs in more well-sorted sediments 01 to 02 mm indiameter in the Port Campbell Limestone This unitis considered to have been deposited in relatively deepwater (Bock amp Glenie 1965) The coarse-grainedcalcarenites of the Mannum Formation representsedimentation in a very shallow water environmentHowever the evolution of A paucituberculata from Atuberculata is not simply a case of adaptation by thedescendant species to inhabiting a finer-grainedsediment The earliest known specimen of A pauci-tuberculata which lacks primary tubercles entirelyoccurs in coarse-grained bryozoal calcarenites of theBochara Limestone It is tempting to speculate thatthis earliest form of A paucituberculata in lackingtubercles and thus defensive spines was adaptedinitially to burrowing deeper in coarse-grained sedi-ments than its ancestor A tuberculata But Apaucituberculata by also having evolved a higher testlonger labrum deeper petals and more sunkenporiferous zones in the petals was also suitablypreadapted to occupying the finer-grained deeper-water sediments of the Port Campbell Limestone

The increase in petal depth which occurs in the Atuberculata-paucituberculata lineage parallels the situ-ation seen in the Schizaster lineage (McNamara ampPhilip 1980) and the Pericosmus lineage (McNamaraamp Philip 1984) Development of more sunken petalsis thought to optimize water flow over the respiratorytube feet in finer-grained sediments Amoraster furtherrefined this adaptation by a swelling of the inter-poriferous zone thus setting each row of respiratorytube feet in a deeper channel Two other morpho-logical changes in Amoraster have also been docu-mented in the Schizaster and Pericosmus lineagesThese are the evolution of a more sunken peristomeand anterior elongation of the labrum McNamara ampPhilip (1980) considered that these changes were alsoadaptations to the habitation of an environmentwhere the flow of water around the echinoid test waslimited to an entrance above the apical systemIngestion of food particularly if the source of thefood was from the sediment surface was improved bythe elongation of the labrum The absence of porepairs in ambulacrum III characteristic of specieswhich possess funnel-building tube feet suggests thatAmoraster did not burrow very deeply into thesediment However as noted above the reduction intubercle number between A tuberculata and A

paucituberculata may perhaps be interpreted as anadaptation to slightly deeper burrowing in thesediment by the descendant species

Most interspecific morphological changes in echin-oids occur by heterochrony (McNamara 1988)Amoraster was no exception Although little is knownabout the ontogenetic changes in the genus thegreater degree of anterior elongation of the labrum inA paucituberculata during growth compared withthat attained by the ancestral A tuberculata indicatesan acceleration in labral growth resulting in theevolution of a peramorphic trait The reduction inprimary aboral tubercle number on the other hand isa paedomorphic feature Such dissociated hetero-chrony with some traits being peramorphic otherspaedomorphic was probably the rule rather than theexception in echinoid evolution (McNamara 1988)and likely to have been a major factor in the highdegree of speciation in spatangoid echinoids duringTertiary time

Acknowledgements We should like to thank Frank Holmesfor the donation of a specimen and Kris Brimmel for thephotography

References

ABELE C GLOE C S HOCKING J B HOLDGATE G

KENLEY P R LAWRENCE C R RIPPER D amp

THRELFALL W F 1976 Tertiary In Geology ofVictoria(ed JGDouglas and J A Waters) pp 177-274Geological Society of Australia Special PublicationNo 5

BAKER G 1950 Geology and physiology of the MoonlightHead district Proceedings of the Royal Society ofVictoria (to 17^44

BOCK P E amp GLENIE R C 1965 Late Cretaceous and

Tertiary depositional cycles in southwestern VictoriaProceedings of the Royal Society of Victoria 79 153-63

CLAUS C 1876 Grudzuge der Zoologie vol 1 (3rd ed)

Marburg and LeipzigFERBER I amp LAWRENCE J M 1976 Distribution sub-

stratum preference and burrowing behaviour of Loveniaelongata (Gray) (Echinoidea Spatangoida) in the Gulfof Elat (Aqaba) Red Sea Journal of ExperimentalMarine Biology and Ecology 22 207-25

GRAY J E 1855 Catalogue of the Recent Echinida or seaeggs in the collection of the British Museum Part 1 -Echinida Irregularia London British Museum (Natu-ral History)

KIER P M 1984 Fossil spatangoid echinoids of CubaSmithsonian Contributions to Paleobiology 55 1-336

KRUSE P D amp PHILIP G M 1985 Tertiary species of the

echinoid genus Eupatagus from southern AustraliaDepartment of Mines and Energy South AustraliaSpecial Publication 5 167-85

LINDSAY J M 1985 Aspects of South Australian Tertiaryforaminiferal biostratigraphy with emphasis on studiesof Massilina and Subbotina Department of Mines andEnergy South Australia Special Publication 5 187-231

LUDBROOK N H 1973 Distribution and stratigraphic

utility of Cenozoic molluscan faunas in southernAustralia Science Reports of the Tohoku University

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms

186 New Miocene echinoid genus

Sendai Japan Second series Geology) Special VolumeNo 6 (Hatai Memorial Volume) 241-61

MCNAMARA K J 1982 Taxonomy and evolution of livingspecies of Breynia (Echinoidea Spatangoida) fromAustralia Records of the Western Australian Museum10 167-97

MCNAMARA K J 1987 Taxonomy evolution and func-tional morphology of southern Australian Tertiaryhemiasterid echinoids Palaeontology 30 319-52

MCNAMARA K J 1988 Heterochrony and the evolution ofechinoids In Echinoderm Phytogeny and EvolutionaryBiology (ed C R C Paul and A B Smith) pp 149-63 Oxford Oxford University Press

MCNAMARA K J (in prep) The role of gastropodpredation in directing speciation in spatangoid echin-oids

MCNAMARA K J amp PHILIP G M 1980 Australian

Tertiary schizasterid echinoids Alcheringa 4 47-65MCNAMARA K J amp PHILIP G M 1984 A revision of the

spatangoid echinoid Pericosmus from the Tertiary ofAustralia Records of the Western Australian Museum11319-56

MCNAMARA K J PHILIP G M amp KRUSE P D 1986

Tertiary brissid echinoids of southern Australia Alcher-inga 10 55-84

MORTENSEN T 1951 A monograph of the Echinoidea 5(2)Spatangoida II Copenhagen Reitzel

SINGLETON O P MCDOUGALL I amp MALLETT C W 1976

The Pliocene-Pleistocene boundary in southeasternAustralia Journal of the Geological Society of Australia23299-311

SMITH A B amp PAUL C R C 1985 Variation in the

irregular echinoid Discoides during the Early Ceno-manian In Evolutionary Case Histories from the FossilRecord (ed J C W Cope and P W Skelton) pp29-37 Special Papers in Palaeontology no 33

SMITH A B amp ZAGHBIB-TURKI D 1985 Les Archiaciidae

(Cassiduloida Echinoidea) du Cretace Superieur deTunisie et leur mode de vie Annales de Paleontologie71 1-33

SPENCER-JONES D 1971 Marginal Tertiary deposits of theTyrendarra Embayment - Grassadle and Hamiltondistrict In The Otway Basin of southeastern Australia(ed H Wopfner and J G Douglas) pp 241-9 SpecialBulletin of the Geological Surveys of South Australiaand Victoria

TENISON WOODS J E 1867 The Tertiary rocks of SouthAustralia Pt IV Fossil Echinidea Papers of theAdelaide Philosophical Society 1865-1866 1-2

httpsdoiorg101017S0016756800006312Downloaded from httpswwwcambridgeorgcore Open University Library on 19 Jan 2017 at 223647 subject to the Cambridge Core terms of use available at httpswwwcambridgeorgcoreterms