Eocene chelid turtles from Redbank Plains, Southeast …sciencepress.mnhn.fr/sites/default/files/articles/pdf/g... · 2015. 5. 6. · turtles are chelids, belonging to at least five

41GEODIVERSITAS • 2001 • 23 (1) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.mnhn.fr/publication/

Eocene chelid turtles from Redbank Plains,Southeast Queensland, Australia

France de LAPPARENT de BROINLaboratoire de Paléontologie, UMR 8569 du CNRS,

Muséum national d’Histoire naturelle,8 rue Buffon, F-75231 Paris cedex 05 (France)

[email protected]

Ralph E. MOLNARQueensland Museum, P.O. Box 3300,

South Brisbane, Queensland (Australia)[email protected]

Lapparent de Broin F. de & Molnar R. E. 2001. — Eocene chelid turtles from RedbankPlains, Southeast Queensland, Australia. Geodiversitas 23 (1) : 41-79.

ABSTRACTThe rich fauna of freshwater turtles from Redbank Plains (Brisbane),Queensland, Eocene (or less probably Palaeocene) includes only Chelidae(Pleurodira). Besides an indeterminate form, five taxa are attributed to two ofthe three extant groups: three taxa to the Chelodina group, and one or two tothe Emydura group, all new, but allowing the erection of only one new spe-cies, C. alanrixi. They show the degree of differentiation that had alreadyoccurred here in the evolution of several of the extant lineages of the twogroups, consistent with the age of the two groups of genera within the family,which has been recorded from the Early Cretaceous of southern Argentina. Itreflects the origin of the Chelidae on a single landmass, Gondwanaland, thefamily representing the southern component of the Pleurodira.

KEY WORDSTurtles,

Chelidae,Chelodina, Emydura,

Eocene, Australia,

new species.

INTRODUCTION (TABLE 1)

In 1990, Dr Alan Rix, of the University ofQueensland, discovered and collected new chelo-nian material from the Eocene deposits atRedbank Plains, Southeast Queensland. Thisincluded the most complete turtle material yetcollected from this site. A further specimen wascollected in 1993. Turtles were first mentioned atRedbank Plains by Jones (1926) who mentioned“Tortoise remains […] apparently identical withChelodina insculpta De Vis […]”. Riek (1952)figured a fragmentary impression of “skinof ? turtle” and mentioned “Fragments of thecarapace and plastron of a turtle […] but they arepossibly only those of a recent specimen”. Theturtle material from Redbank Plains was consi-dered as “Testudines indeterminant” in the firstsynthesis of fossil turtles of Australia (Gaffney1981: fig. 5). Part of the newly collected materialhas been mentioned as “chelid material” andfigured by Rix (1991). Study of the new materialin this paper shows that the Redbank Plainsturtles are chelids, belonging to at least five taxa.Other possibly Eocene chelid material fromQueensland has been found at Rockhampton,Proserpine and Cape Hillsborough. The geologyof this region is still poorly understood andundergoing further description, thus some units

still lack formal stratigraphic names and correla-tion is tentative. What Gaffney (1981) termed“Testudines indeterminant” and then “chelidmaterial being in press” (Gaffney 1991) comesfrom Queensland geological Survey bore num-ber 2, Rockhampton, of the mid to late EoceneRundle Formation (Henstridge & Coshell 1984).This bore is actually just outside Gladstone(Henstridge & Coshell 1984) where abundantturtle remains have recently (August, 1999) beencollected from a bonebed in the Kerosene CreekSeam of the Rundle Formation, near Gladstone.This material consists of articulated and disarti-culated shells, isolated limb elements and girdles,and at least one mandible. The fossils seem tooccupy a single level only a few centimetres thick,and only sporadic bones or teeth (crocodilian)occur outside this level. The collected materialsuggests at least five individuals per square metre.A broken shell (QM F14318) from the Condoroil shale near Proserpine, between Bowen andCape Hillsborough, is still under preparation.This shell pertains to Emydura s.l. sp. (see below)but its age relative to the Redbank Plains speci-mens is unclear. It is given as “lower Tertiary”,with palynological studies giving a range of“Palaeocene to middle Oligocene” or “Eocene toMiocene” (Paine 1972; Green & Bateman 1981)depending where in the strata the specimen has

Lapparent de Broin F. de & Molnar R. E.

42 GEODIVERSITAS • 2001 • 23 (1)

RÉSUMÉTortues chélidées de l’Éocène de Redbank Plains, Queensland du sud-est,Australie.La région de Redbank Plains, à côté de Brisbane, Queensland, a livré uneimportante faune de tortues d’eau douce, attribuée aux seuls Chelidae,Pleurodira, avec deux des trois groupes de genres australiens actuels de lafamille. Outre une forme indéterminée, trois taxons sont attribués àChelodina s.l. et un ou deux à Emydura s.l. Seule l’espèce C. alanrixi est créée,les autres espèces reposant sur du matériel insuffisant quoique nouveau dansle contexte des Chelidae connus. La localité, paléogène, est attribuée à l’Éo-cène au plus tard. La différentiation déjà nette de plusieurs lignées au sein desdeux genres confirme son ancienneté, étant en accord avec l’âge de la famille,représentée depuis le Crétacé inférieur du Sud de l’Argentine. Elle reflètel’origine des Chelidae sur un continent unique, le Gondwana, la famillereprésentant le composant sud des Pleurodira.

MOTS CLÉSTortues, Chelidae

Chelodina, Emydura,

Éocène, Australie,

nouvelles espèces.

come from and on the exact location of the speci-men. The Condor oil shale may be part of theCape Hillsborough Beds or the Plevna beds.Turtle shell fragments (QM L1190), attributedto Chelidae, also derive from the “Wedge Islandbeds”, the lower unit of the Cape HillsboroughBeds, of middle Eocene age, at Wedge Island,Cape Hillsborough (McNamara 1994).Other, nearly contemporaneous material fromSoutheast Queensland, is either very fragmentaryor yet unprepared and thus has not been revised.Fragments of both carapace (UQF 17494-UQF 17510) and plastron (UQF 24020), someover 1 cm thick, were collected in 1954 from awell penetrating the Corinda Formation in theBrisbane suburb of Eight Mile Plains (Cranfield

et al. 1989; Willis & Molnar 1991). They arebelieved to be Eocene (Hill & Denmead 1960).De Vis (1897) mentioned other material fromEight Mile Plains including it in the descriptionof Chelodina insculpta, along with material fromthe Plio-Pleistocene of the Darling Downs,Queensland, and the Warburton River, SouthAustralia. Unfortunately, he did not specifywhich specimens came from which locality, so itis not possible to confirm the presence ofChelodina at Eight Mile Plains. However, hisfigures (De Vis 1897) show that he did notconfuse the Emydura and Chelodina groups, thetwo main Australian chelid groups, so that thepresence of Chelodina in Eight Mile Plains is pos-sible, even if the figured material is only from

Eocene turtles from Australia

43GEODIVERSITAS • 2001 • 23 (1)

TABLE 1. — Oldest chelid or possible chelid records in Palaeogene of Australia.

Name First mention Palaeocene Eocene Oligocene

Chelidae indet.?

Chelodina alanrixin. sp. a, sp. b, sp. c, Emydura s.l. sp. a and b?, 1 indeterminate

Emydura s.l. sp.

Chelidae? (not studied)

Chelidae(not studied)

Chelodina sp.

pro parte Chelodinainsculpta De Vis inJones, 1926, pro parte “indeterminant”(Gaffney, 1981)

Chelidae (Gaffney,1991; McNamara,1994)

“indeterminant”(Gaffney, 1981)

Chelidae(Gaffney, 1991)

Chelodina insculptaDe Vis, 1897 givenas Chelodina sp. inGaffney, 1981

BoongeroodaGreensand, WA

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

Eight Mile Plains,Runcorn, nearBrisbane, Q, Corinda F. (?Eocene)

Wedge Island at CapeHillsborough, Q, CapeHillsborough B.,Wedge Island beds,middle Eocene.Rockhampton, nearGladstone, Q, RundleFormation (mid- to lateEocene)

Redbank Plains, Q

15.5 km SSE Proserpine Q, Cape Hillsborough B.

Eocene to Pleistocene: mixed Eocene of Eight Mile Plains, Q + Plio-Pleistocene of Darling Downs, SQ, and Warburton River, SA (lectotype and other figured material from Darling Downs)

(Palaeocene to middle Oligocene)

Darling Downs (Thomson in prep.) and, particu-larly, the lectotype designed by Gaffney (1981).Regarding the Warburton River material, Plio-Pleistocene sediments of the Katipiri Sands,which yielded Chelodina insculpta (fide Vickers-Rich & Rich 1993: fig. 259) proceed from themargins of this river. Gaffney (1981: fig. 18A)figured as “Chelidae” a specimen attributable toChelodina, from the Katipiri Formation at LakeKanunka, South Australia, Southwest of theWarburton River in the same area. Two turtle fragments have been collected (byJohn Long, Western Australian Museum) in thePalaeocene Boongerooda Greensand, at Pilbara,just South of Exmouth Gulf, western Australia.They are indeterminable although probably che-lids fragments. One is thick and smooth as areseveral Emydura s.l. including Pelocomastes DeVis, 1897 (an Elseya specimen, Thomson pers.comm.). The other is thinner and decorated withsmall polygons, like those observed in chelids.With the exception of the shell from nearProserpine (QM F14318) and the newly collect-ed material from Gladstone, none of this materialis as complete as that from Redbank Plains.There is much material of older Australianturtles, from the Early Cretaceous. Followingcareful observation of the specimens in 1993, wethink that all this material is clearly cryptodiran,not pleurodiran. On the one hand there is marineChelonioidea (sensu Hirayama & Chitoku 1996),including Cratochelone Longman, 1915 andNotochelone Lydekker, 1889, from the AlbianToolebuc Formation, Queensland, the latterattributed to the protostegid lineage (Gaffney1991). There is also a new cryptodiran form,from the Toolebuc near Boulia, westernQueensland (Queensland Museum). On theother hand, there are freshwater taxa, also belong-ing to Cryptodira. There is a new form (Molnar1991: pl. 1), from the Cenomanian WintonFormation near Winton, Queensland (Queens-land Museum). There are also various elementsfrom the late Aptian and early Albian of Victoria(Rich & Rich 1989; Dettmann et al. 1992)(Museum of Victoria and Monash University)and from the Early Cretaceous Griman Creek

Formation of Lightning Ridge, New SouthWales (Warren 1969b; Molnar 1980; Dettmannet al. 1992) (casts in the Australian Museum,Museum of Victoria and Queensland Museum).Chelycarapookus Warren, 1969, from theCasterton neighbourhood, Victoria, is definitelya primitive cryptodire, not a pleurodire contrarilyto a previous assessment: a hypothesis still erro-neously given (Manning & Kofron 1996) in spiteof recent work to the contrary (Gaffney 1991)recently confirmed (Gaffney et al. 1998).Observation of the holotype specimen allows areconstruction of a rounded-oval shell, with ple-siomorphic characters such as anteriorly- andposteriorly-wide intervertebral canal, wide verte-brals (much wider than the costals) and widenuchal and cervical; the plastron has short plas-tral lobes, rounded (relatively derived state), aprimitive long entoplastron and no central plas-tral fontanelle. In Victoria, there are also primi-tive cryptodiran turtles including OtwayemysGaffney et al., 1998, from the Slippery Rock site,Dinosaur Cove, Otway group, Aptian-Albian,Cape Otway, and an unnamed form from EaglesNest, Cape Patterson, Strzlecki group, Aptian(Victoria Museum). Otwayemys is considered byits authors (Gaffney et al. 1998) as close either tothe Meiolaniidae (Late Cretaceous-Pleistocene,Patagonia, Australia and neighbouring islands) orto some Asiatic genera from Early Cretaceous(Sinemys, Dracochelys-Hangaïemys, Ordosemys),on the base of the evolutionary grade of the isola-ted elements attributed to Otwayemys. These taxaare cryptodiran turtles of an evolutionary gradewithout mesoplastra and with vertebrae withformed joints (condyles, cotyles). The material fromthe Otway retains some primitive characters inthe proportions of the elements (shell, vertebrae)which allow us to think that they are more primi-tive than the compared Asiatic taxa. The differ-ence between Chelycarapookus and Otwayemys isestablished. Some turtle elements from the EarlyCretaceous of Lightning Ridge, New SouthWales (Molnar 1980; Dettmann et al. 1992)show the possible presence of Otwayemys in opis-thocoelous (AM F72276) and amphicoelous(AM F68245) cervical vertebrae, short and high,



with a dorsal spine and double transverse pro-cesses (separated tuberculum and capitulum for adouble headed cervical rib). However, one speci-men of cervical vertebra 4 from Lightning Ridge(AM F68254) is distinct from Otwayemys, repre-sented by the preserved cervical 8 (unfortunately,the cervical 5 attributed to Otwayemys is not fig-ured in Gaffney et al. 1998). It has a longer andlower centrum and a lower neural spine than theother vertebrae from Lightning Ridge and thecervical 8 attributed to Otwayemys; it has a strongtransverse apophysis, not a double headed cervi-cal rib; it is biconvex as in some cryptodires(third, fourth, eighth) and – and this is interest-ing – as in some pleurodiran cervical vertebrae:as in Chelidae (fifth and eighth) and inPelomedusoides (axis); the transverse apophysis isat the anterior-mid length of the neurocentralsuture, as in some cervicals of primitive crypto-dires (only) and as in vertebrae of theEupleurodira (Chelidae and Pelomedusoides).However, as it cannot be an axis (because of thedifferent position of the prezygapophyses and theabsence of an anteriorly protruded neural spine)and as it lacks a common pedicle for the postzy-gapophyses, it cannot be attributed to theEupleurodira (including the Chelidae). Althoughit has a more lowered neural spine, it resemblesthe fourth cervical of the cryptodiran Ordosemysleios Brinkman & Peng, 1993, from the EarlyCretaceous of Mongolia, better than thevertebra 8 attributed to Otwayemys resembles tothe eight of this Asiatic genus. All of these EarlyCretaceous turtles are peculiar to Australia. Theymay have common ancestors with Asiatic forms(Gaffney et al. 1992, 1998) or Late JurassicNorth American forms (Gaffney 1981), in otherwords they are related to taxa developed in theLaurasiatic part of the Pangea. It has already been shown (Gaffney 1981;Gaffney et al. 1989) that the comparative studyof the osteology of the extant Australian chelidsremains to be done so that is not possible to dis-tinguish between the taxa – genera or species – ofthe extant Australian chelids from the postcranialskeleton. Neither the definition of the characters(morphology of the elements, their decoration),

allowing a distinction between the taxa nor theresearch of their phylogenetical relationships, isyet available. This explains why much fossil che-lid material is considered indeterminate (Gaffney1979, 1981) although some identification is pos-sible by comparison with material of extant che-lid taxa. Study of the Redbank Plains materialpresents the opportunity of revealing some newdistinguishing features, although it does not pre-tend to resolve all problems.The material described here is not only the oldestdescribed Australian Cenozoic turtle material,but also the oldest Australian specimens definite-ly attributable to freshwater chelids. It shows thatby this time the Australian group was alreadydiverse with large and small forms of theChelodina and Emydura groups. It supports thecurrent palaeoecological interpretation of theRedbank Plains Formation as having been depo-sited in a large, shallow lake.

OCCURRENCE AND AGE

The fossils occur in large ironstone nodulesfound in the soil at Redbank Plains and clearlyderiving from the Redbank Plains Formation.This unit consists of mudstones, clays and fissileshales, with white to light grey sandstones(Staines 1960). A basalt from the overlyingSilkstone Formation has been dated at 45 my.(Green & Stevens 1975; Cranfield et al. 1989),so that the Redbank Plains Formation is at leastEocene in age. This age is generally accepted,although it may be as old as Palaeocene. Thevertebrate fossils usually occur in ironstonenodules, weathered out of the shales, and oftenthe bone originally within the nodules has beenlost to weathering, so that only fragments andnatural molds remain. As the matrix of thenodules is fine-grained, these molds preserve finedetail. This locality has yielded a fauna of fish (mostlyteleosts, but with a dipnoan) and invertebrates,including insects, ostracods and a bivalve (Uniosp.) (Riek 1954; Staines 1960; Kemp 1991). Areport of crocodilian material, including impres-sions of the skin (Riek 1952), so far has not beensubstantiated, however the impression of the foot



of a large, ground-dwelling bird was recovered in1989 (Vickers-Rich & Molnar 1996).Beasley (1945) reconstructed the environment ofdeposition of the Redbank Plains Formation as ashallow, permanent lake with a floor of “mud,decayed vegetable matter and algae” (Beasley1945: 122). This conclusion is supported by largespecimens of teleosts and the dipnoan and isconsistent with the turtle material describedherein.

MATERIAL

The Queensland Museum collection includesseveral specimens collected on the slopes East ofJones Road, Redbank Plains, near Brisbane(notably QM F18344) and on the slope above(West of) the former Redbank Plains refuse tip(QM F31697). Five individuals belong to four tofive different species (Table 2) and the two otherspecimens examined either belong to one of thesespecies or are indeterminate. The specimens have been compared with theextant and fossil Pleurodira, from Triassic to pre-sent times, particularly with the extant Australianchelid genera: the comprehensive EmyduraBonaparte, 1836 s.l., a group including EmyduraBonaparte, 1836, Elseya Gray, 1867 andRheodytes Legler & Cann, 1980 (and Elusor Cann& Legler, 1994, and not observed); Pseu-demydura Siebenrock, 1901; and ChelodinaFitzinger, 1826. The characters allowing to dis-tinguish the genera of the Emydura group are notyet established and given together in a compar-ative cladistic study. The comparative material,consisting of some prepared shells and mainlyunprepared shells (with scutes and with plastronsutured to carapace) is principally that of theZoology and Palaeontology departments of theAustralian Museum, Sydney, the QueenslandMuseum, Brisbane, the South AustralianMuseum, Adelaide, the Western AustralianMuseum and the collection of the Dr GeraldKuchling, University of Western Australia, Perth,the Muséum national d’Histoire naturelle, Paris,the Natural History Museum, London. Alsoexamined were specimens from the NationalMuseum of Victoria, Melbourne, the American

Museum of Natural History, New York, theDepartamento Nacional da Produçao Mineral,Rio de Janeiro, the Museu de Zoologia daUniversidade de São Paulo, the Museo deCiencias Naturales de Buenos Aires, the Museode Ciencias Naturales de La Plata, the Museumfür Naturkunde, Humboldt-Universität zuBerlin, the Naturmuseum Solothurn, theStaatliches Museum für Naturkunde-Stuttgart,the Zoologische Staatssammlung München.

ABBREVIATIONSQM Queensland Museum, Brisbane;MNHN Muséum national d’Histoire naturelle,

Pa r i s (AC, Ana tomie comparée ;H, Zoologie des Reptiles et Amphibiens;P, Paléontologie);

BMNH the Natural History Museum, London;UQF University of Queensland Geology

Museum, Brisbane;UWA University of Western Australia, Nedlands,

Perth;WA Western Australian Museum, Perth.

SYSTEMATICS

Order CHELONII Brongniart, 1800Sub-Order PLEURODIRA Cope, 1864

Family CHELIDAE Gray, 1825Genus Chelodina Fitzinger, 1826

Chelodina alanrixi n. sp.

HOLOTYPE. — QM F18344, a nodule with a part ofthe external and internal impressions of the carapace(Figs 1-3 ; Table 2).

ETYMOLOGY. — In honour of Prof. Alan Rix, of theUniversity of Queensland, in recognition of his contri-butions to both invertebrate and vertebrate palaeontol-ogy of the Early Cenozoic in Australia.

LOCALITY AND STRATIGRAPHIC HORIZON. — The spec-imen was collected on the slopes East of Jones Road,Redbank Plains, near Brisbane, Queensland, Australia.Redbank Plains Formation, Early Cenozoic, at leastEocene if not Palaeocene time.

DIAGNOSIS. — A new large species of Chelodina with-out particular widening or narrowing of the carapaceand narrowing of the vertebral 5, but with very nar-rowed vertebrals 2 to 4. Similar to the extantC. expansa Gray, 1857, by its large size and shell pro-



portions, the high degree of pygal-peripheral overlapby the costals and vertebral 5, the nearly flattened pos-terior border slightly pointed and not medially raised,the iliac scar shape and the presence of a strong iliacscar crest. More primitive than C. expansa by thesmaller polygons, the wider vertebral 5, still complete-ly wider than the suprapygal, and by the completeseries of neurals, although not contacting the supra-pygal; more derived than C. expansa by the relativelymore narrowed vertebrals 2 to 4 as in the extant elon-gated C. oblonga Gray, 1841 and in C. longicollis(Shaw, 1802). Different from the Redbank Plainsform 2 of Chelodina which is a small rounded form.Different from C. insculpta De Vis, 1897, in thegreater size of the shell and the relatively smaller sizeand morphology of the polygons and the greater widthof vertebral 5. Presumably distinct from form 3 ofChelodina from Redbank Plains, in the greater size ofthe shell, the relatively smaller polygons and the pre-sumed absence of an upwardly-curled border.

DESCRIPTION

Material (Figs 1-3; 10; Tables 2; 3)Form 1 of Chelodina from Redbank Plains,C. alanrixi n. sp., is represented by QM F18344.It consists of a single nodule, broken in severalparts by weathering. The principal elements arethe external impression of the dorsal face of theright lateral and posterior part of a shell (Fig. 1B)in reversed relief, the impression of the ventralface of the posterior part of the shell, superposedon the external impression of some shell plates, inreversed relief (Fig. 1A) and a fragment with theventral aspect of the medial part of the shell.

Measurements (in cm)Preserved longitudinal length of shell: 37.5.Estimated total longitudinal length of shell: c. 40-41.Preserved posterior width of shell: 26.Estimated posterior width of shell: 30.Vertebral 4, maximal width: 4.9.Vertebral 5, maximal width: 10.2.Suprapygal, maximal width: 8.3.Peripheral 10, anterior length/external width:c. 4.8/5.1 = c. 94%.

DecorationThis consists of very well-marked, small, salient,elongate or rounded polygons. These appearhere, owing to the reversal of relief, as elongate

and rounded pits separated by sharp crests. Thepolygons, narrow, vary from c. 9-2 mm long overc. 2.5-1 mm wide. Medially, in the area of thevertebrals, they are longitudinally elongate; onthe lateral part of the shell, in the area of the cos-tals, they are transversally elongate; on the lastpleurals they are obliquely oriented and theirelongation follows the external margin on theperipherals. The polygons are uniformly distribu-ted on the carapace. As in Chelodina and inPseudemydura, they are more marked and moreevenly distributed than in those Emydura s.l. witha partly polygonal decoration. In those forms, thepolygons of the carapace are weakly developedand poorly formed, a derived condition relativeto the primitive decoration (see below); there aredichotomous sulci, smooth areas, granulations,pits, sharp crests or rounded ridges characteristicof the Emydura s.l. lineage, whether or not poly-gons are present. Examples of the decoration ofthe Emydura group can be seen in Gaffney (1981:figs 10-12) and in the figures of De Vis (1897:pls I-IV), showing the polygons weakly develo-ped, crests and ridges; figures of finely ridged spe-cimens of Emydura s.l. from the Miocene ofSouth Australia are given by Gaffney (1979,1991). Another part of the fossil material of DeVis (1897: pl. V) attributed to Chelodina insculp-ta De Vis, 1897 shows a typical decoration ofextant species of Chelodina. But some of the cara-pace fragments referred to the species (pl. V, H, asuprapygal) show polygons smaller than usual inextant Chelodina and than in the other referredfragments, including the lectotype designed byGaffney (1981) and more similar in size to thoseof the Redbank Plains material of Chelodina. Thesmall, marked, well-distributed dorsal polygonsof Pseudemydura are all rounded (not elongate) inform and, as a whole on the shell, smaller than inthe other living species.The plastral polygons are less different inChelodina and Pseudemydura than in theEmydura group, when present in the latter. Thepolygons are, in general, more weakly developedand more elongate in Emydura s.l. Comparisonmay be made using Gaffney (1981), specimensfrom the Miocene of South Australia, fig. 15,



with the more elongate polygons, and fig. 18B-C,with the more elongate polygons and fine ridges,compared to fig. 18A (Pleistocene of SouthAustralia), all being given as Emydura. The latteris in fact a Chelodina specimen, as shown by therounded posterior form of the ischiadic scar onthe xiphiplastron (derived character state foundin extant Chelodina), as opposed to the posteriorly-pointed form in Emydura s.l. and Pseudemydura(plesiomorphic character state). The decorationof the plastron of C. insculpta De Vis, 1897(pl. VI), with rounded polygons, is also typical ofChelodina, with polygons intermediate in sizebetween old specimens of C. expansa and C. lon-gicollis. The lectotype (designed by Gaffney1981) of C. insculpta De Vis, 1897, 5 cm long,shell around 27 cm long, bears around 30 poly-gons along the medial line, the entoplastron ofC. longicollis (MNHN AC 1911-181), 3.7 cmlong, shell 20 cm long, bears around 35 narrowerpolygons while the entoplastron of the specimenof C. expansa (MNHN AC 1914-178), 6.2 cmlong, shell 37.5 cm long, bears only 22 largerpolygons along the medial line. Granulate andwell-marked plastral polygons are also found in aspecimen from Redbank Plains, possibly belong-ing to Chelodina sp. c (see below), but the poly-gons are more clearly longitudinally oriented andsmaller than in C. insculpta.Confusion of isolated parts (those with roundedpolygons) of the shells of Chelodina for those ofPseudemydura is possible. In the present case, theother associated parts of the shell indicate thatthe Redbank Plains specimens do not pertain toPseudemydura. A polygonal or granulate decora-tion is primitive for turtles, found in Triassicspecimens from Germany (Proganochelys,Proterochersis). It is retained in Notoemys (weaklydeveloped polygons), a pleurodiran from the LateJurassic of Argentina. The decoration consistingof dorsal and ventral polygons that radiate from acenter is probably primitive for chelids, as poly-gons so oriented are found in nearly all chelids,from the Late Cretaceous (of Argentina) to thepresent. The decoration of polygons is howeververy little developed in the first known chelids(Aptian-Albian of Argentina) (Lapparent de

Broin, Fuente & Calvo 1997). They, however,represent only a part of the chelid groups and thepolygonal decoration is more widely distributedin the various species of the Late Cretaceous thatbelong to all the chelid groups. The decoration ofpolygons is particularly developed in the groupsincluding Hydromedusa, Chelodina andPseudemydura, it is variably developed in thePhrynops and Emydura groups and is nearly com-pletely absent in some fossil forms: the primitivearrangement of the polygons evolved indepen-dently in the lineages, either weakening or deve-loping and, as shown above, it is possible todistinguish the three Australian groups. The shellon the whole has narrower and more markedpolygons in C. alanrixi n. sp than in C. expansa,the living species of Chelodina of equivalent size.They are distinct from the fragments attributedto Chelodina insculpta De Vis, 1897. In this spe-cies, as previously noted, De Vis (1897) includedmaterial from the Eocene of Eight Mile Plains,Queensland, as well as from the Plio-Pleistoceneof Darling Downs, Queensland, and of theWarburton River area, South Australia. Some ofthe material therefore could be contemporaneouswith C. alanrixi n. sp. and could be conspecificwith it. However, the figured fragments of C. ins-culpta are relatively smaller, from a carapaceabout 27 cm long for the entoplastron (lectotype)of 5 cm. The shell of the reconstructed plastronin De Vis (1897) has 30 cm (Thomson pers.comm.). It is a little longer than, for exampleC. longicollis, with shells 18-22 cm long, withinthe limits of C. expansa, with shells up to 42.3 cmlong (Goode 1967) and C. alanrixi n. sp., shellaround 40-41 cm long. The decoration of theposterior elements of the carapace of C. insculptawhich are comparable to those of C. alanrixin. sp. has relatively more rounded and widerpolygons (pleurals, peripherals) and more roundedand smaller polygons (suprapygal), more similar tothose of the living C. longicollis than to C. expansa(see Fig. 10D) and C. alanrixi n. sp. (Fig. 1B).

Carapace shapeThe shell is that of a fully adult animal, well-grown with well-sutured plates. It was probably





FIG. 1. — Chelodina alanrixi n. sp., form 1, Redbank Plains, Queensland, Eocene (QM F18344); A, posterior part of the shell, impres-sion of the superposed internal and external parts; B, lateroposterior part of the shell, impression of the external face. Scale bar:5 cm.

A

B

moderately elongate (Fig. 10A), probably show-ing the primitive condition for shell elongation in Chelodina, the ratio of width to (presumed)length estimated as 73-75%. This percentage(Table 3) is that of moderately elongate livingChelodina, such as the largest, C. expansa and thesmaller C. longicollis; it also enters in the range ofthe still shorter species, C. reimanni Philippen &Grossmann, 1990, C. pritchardi Rhodin, 1994and C. mccordi Rhodin, 1994 (the distinguishingosteological shell characters of these speciesremain unknown). The percentage is in the lowerrange for the small C. novaeguineae Boulenger,1888, and of the rounded C. steindachneriSiebenrock, 1914. It is in the higher range for themedium-size, more elongated or narrowed spe-cies, the C. rugosa Ogilby, 1890 – C. siebenrockiWerner, 1901 group and C. oblonga (see shellsfigured in Burbidge et al. 1974; Goode 1967;Philippen & Grossmann 1990; Rhodin 1994a, b;Rhodin & Mittermeier 1976). Individual varia-tions, including sexual and ontogenetic variation,and overlap between species are all possible. Theestimated ratio of C. alanrixi n. sp. indicates that

it was not a short rounded form nor a very elon-gate or narrow form. It, therefore, has a relativelyundifferentiated shell form within the genus inthis respect. The posterior border is short, round-ed and slightly medially pointed as C. expansa(borders of both not as short as in C. oblonga)(pointed as in males of C. expansa, more than infemales), not convex and raised at the pygal as inC. longicollis and not particularly convex, curvedand narrowed ventrally as in Pseudemydura. It isalso not elongated and posterolaterally expandedas in the Emydura group.

Dermal bonesFrom the right side of the shell – that is on theleft side in Figs 1B and 2, a partial impression ofthe eight pleurals is preserved. Only the posteriorborder of pleural 1 may be seen, but pleurals 2-4are nearly complete, 5-6 lack the medial borderand 7-8 are complete. On the left, pleurals 6(incomplete) and 7-8 are preserved. These pleu-rals were connected to the medial neurals. Theneurals 1 (incomplete), 2-4, 7 (also incomplete)and 8 are preserved. It is evident that there was acomplete series of eight neurals, the first qua-drangular, the following hexagonal-short-sided infront, and the last pentagonal: the series does notcontact the suprapygal, instead the pleurals 8meet behind the small pentagonal neural 8.The presence of a complete neural series is primi-tive and, furthermore, also plesiomorphic foreach South American chelid genus, as demon-strated by the early fossil record (from the Albianand Senonian-Maastrichtian of Argentina, Broin& Fuente 1993; Lapparent de Broin et al. 1997;Fuente et al. 2001). In the primitive chelonianseries, known since Late Jurassic, neural 1 orneurals 1 and 2 are hexagonal short sided behindand the first quadrangular neural is 2 or 3.Neural 8 contacts the suprapygal. In Patagonianchelids, reduction of the neural series is alreadyshown by the Albian in a form similar to thesmall species of the group Phrynops Wagler, 1830– Acanthochelys Gray, 1873 (Lapparent de Broinet al. 1997). In Late Cretaceous times, Senonian-Maastrichtian, it appears in forms without livingrelatives and in forms related to Phrynops and



FIG. 2. — Chelodina alanrixi n. sp., form 1, Redbank Plains,Queensland, Eocene (QM F18344), lateroposterior part of theshell, impression of the external face. Abbreviations: C4, costalscute 4; M12, marginal scute 12; n8, neural 8; per. 10, peripher-al 10; py, pygal; spp, suprapygal; V5, vertebral scute 5. Scalebar: 10 cm.

C4

V5

M12 pyspp

n8

per. 10

Hydromedusa Wagler, 1830, at least (Broin &Fuente 1993). In South American chelids, com-plete reduction appears only in the Phrynopscomplex: in Platemys Wagler, 1830, Acanthochelysand in some species of Phrynops s.l. (Bour &Pauler 1987; Broin & Fuente 1993; Fuente1988, 1992; Fuente & Ledesma 1985; Kischlat1991; Perea et al. 1996; Pritchard & Trebbau1984; Sanchez-Villagra et al. 1995a, b; Wood1976; Wood & Moody 1976; specimens of visit-ed Museums). In Australian chelids (Boulenger1889; Burbidge et al. 1974; Cann & Legler 1994,Legler & Cann 1980; Rhodin & Mittermeier1976, 1977; Thomson & Georges 1996; speci-mens of visited Museums), the tendency for neu-ral reduction is common to all the genera, buteach genus has done so at a different rate. InAustralia, reduction of the neural series is moremarked (complete) in Pseudemydura. It is com-plete or nearly complete in the members of theEmydura complex, as early as Eocene. Neurals arelost in Emydura s.l. sp. from the Condor oil shalenear Proserpine (QM F13687). Neurals are rare,and often incomplete, in specimens given asEmydura sp. from Tasmania (Warren 1969a) andin some specimens of the extant Elseya latister-num Gray, 1867 and E. novaeguineae (Meyer,1874) (see Rhodin & Mittermeier 1977), Elseyasp. aff. latisternum from Manning River andElseya sp. from South Alligator River (Thomson& Georges 1996; a new determination is given inThomson in prep., pers. comm.) and only theventral part of the posterior neurals remains inEmydura s.l. sp. a (Redbank Plains form 5). Inthe specimens of Chelodina, examined, the reduc-tion is either always complete and not submittedto individual variations (C. expansa, see Fig. 10B,C. rugosa, C. steindachneri), much pronounced(C. siebenrocki, C. novaeguineae) or slightly pro-nounced (C. oblonga). In the former, the ventrallayer of the neurals is preserved below the pleuralswhich meet over them as in Emydura s.l. sp. a(Redbank Plains form 5) and this may be presentin many South Australian chelids (Thomson &Georges 1996). This shows that the reductionoccurred independently in each lineage ofEmydura s.l. as well as of Chelodina and that

C. alanrixi n. sp. has a primitive character statewith a complete series of neurals, but alreadywith the first neural quadrangular and neural 8not contacting the suprapygal. This morphologyindicates that it may be at the base of one of thelineages leading to extant Chelodina species. The posterior border is represented by the peri-pherals 8-11, on the right side and the pygal andthe peripherals 9-11 on the left. The pleurals arewell-sutured with the peripherals and the dorsalrib extremities well-fused in the dermal plates,without any salient ventral part and any free ribextremity, appropriate for a large adult withoutpermanent fontanelles with their intercalated car-tilaginous tissue. The peripherals are relativelywide, for example for peripheral 10 the ratio ofanterior length to external width is 94%. Amongextant forms, this ratio is comparable to that ofChelodina (84% in C. oblonga, 106% in C. stein-dachneri, 107% in C. expansa, 116% in C. longi-collis) and Pseudemydura (93% and 121%, fromtwo specimens). The value is higher in theEmydura group although a slight overlap betweenthe two groups exists: 105% in Elseya latisternum;115% and 141.5% in E. novaeguineae; 137% inE. dentata (Gray, 1863); 120%, 129% (holotype,MNHN H 9409) and 137% in Emydura mac-quarrii (Gray, 1831); 140% in the specimenQM J31703 attributed to Rheodytes leucops Legler& Cann, 1980; 171.5% in a specimen from theMNHN (H) coll. attributed to E. australis (Gray,1841), a specimen apparently conform to theholotype, BMNH 47-3-4-36; see Goode 1967(Thomson pers. comm. suggests that the speci-mens identified here as E. australis are of E. victo-riae [Gray, 1842] that he separates from theformer with which it was synonymized). The pos-terior peripherals have the most derived condition,for Australian chelids in the Emydura group – nar-rower and more elongated – although they are aswide as in some Chelodina in the less derived spe-cimens such as in Elseya latisternum and in somespecimens of E. novaeguineae. However, in all theEmydura group species, they are more elongatethan in C. alanrixi n. sp. The measurements of theperipherals of C. alanrixi n. sp. are fully concordantonly with those of Chelodina and Pseudemydura



specimens. Actually, the primitive turtle form ofthe border, and the original form in the pleuro-dires in particular, is not expanded anteriorly orposteriorly. These include Proterochersis Fraas,1913, from the Triassic of Germany (specimens inthe Staatliches Museum für Naturkunde-Stuttgart), Notoemys Cattoi & Freiberg, 1961,from the Late Jurassic of Argentina (specimensfrom Museo de Ciencias Naturales de La Plata,Museo de Ciencias Naturales de Buenos Aires; Fuente & Fernandez 1989; Fernandez &Fuente 1994), and Platychelys Wagner, 1853,from the Late Jurassic of Germany andSwitzerland (specimens in NaturmuseumSolothurn; Bräm 1965). The shell border isslightly elongated anteriorly and posteriorly inPseudemydura, much more elongated anteriorlyand slightly posteriorly in Chelodina and slightlyelongated anteriorly and much more elongatedand expanded posteriorly in Emydura s.l. Parallelevolution produced similar forms in each of theSouth American chelid groups as well as in thenorthern Gondwanian Pelomedusoides but,linked to other characters, these still representimportant diagnostic features for each genus orgroup of species.The suprapygal and pygal are similar to those ofC. expansa: the suprapygal is pentagonal butnearly rhomboid and the pygal is more narrowedanteriorly. The suprapygal shape is also more

anteriorly triangular in C. alanrixi n. sp. than inC. insculpta De Vis, 1897. That suprapygal ofthat species, rather similarly to that of C. longicol-lis, bears the borders of the vertebral 5, this scutebeing narrowed as in the extant relatively elon-gated forms, including C. longicollis (see below)and different from that of C. alanrixi n. sp. Thefigures 1A and 3 show the scars for the suturalattachment of both ilia below the posterior cara-pace. This is a typically pleurodiran character in thesuture of the pelvis to the shell: in the Pleurodira,relative to the primitive state in turtles, the pelvisis reduced in width at least to the size of the pos-terior lobe (or even narrower). This has becomebifid to receive the points of the ischia(Lapparent de Broin & Fuente 1996). The dorsalsurface of the iliac blade is widened and short-ened and sutures to the carapace. The pubis andischia become vertical and their ventral extremi-ties suture with the plastron. The shape of theiliac scar of C. alanrixi n. sp. is a trapezoid withrounded angles, the anterior side directed medial-ly, as long as wide and occupying most of the sur-face of pleural 8 and overlapping the suprapygalby a wide, rounded triangular area. The shape ofthe iliac scar is variable in chelids. It is primitivelytriangular in chelids and it remains so or rathertriangular in Emydura s.l., becomes more elonga-te and rounded-oval in Pseudemydura and it ismost often oval or triangular (but much round-ed) in Chelodina. There is parallel evolution ineach South American chelid group. The length ofthe scar below pleurals 7 and 8 and the suprapy-gal varies much. If the scar is wider or both short-er and wider, it is more derived: the primitivepleurodiran scar being narrow and prolongedfrom pleural 7 to the peripherals. In chelids thescar has a tendency to be reduced anteriorly sothat it does not contact pleural 7 any more. Theilium also tends to maintain – but eventually toexpand in width – its contact with the suprapygal(the pelvis becoming more posteriorly sutured tothe shell). This condition is different from that ofthe Pelomedusoides where the tendency is toreduce the contact with the suprapygal (thecontact most often disappears, with the pelvismore anteriorly sutured to the shell) (Lapparent



FIG. 3. — Chelodina alanrixi n. sp., form 1, Redbank Plains,Queensland, Eocene (QM F18344), posterior part of the shell,impression of the internal face of the Fig. 1A. Abbreviations: il,iliac scar below pleural 8 and suprapygal; M12, marginalscute 12; pl8, pleural 8; py, pygal; spp, suprapygal. Scale bar:5 cm.

pl8

spp

py

M12

il

de Broin & Fuente 1996; Lapparent de Broin &Murelaga 1999). The anterior contact of the scarunder pleurals 7-8 is not preserved in C. alanrixin. sp., but, judging from the part preserved, thescar ought to be little developed in pleural 7 orlimited to the suture between the two pleurals, asin C. expansa.The scar is a depressed region on the pleurals,well-delimited and nearly smooth. But dorsalrib 9, which is enveloped in pleural 8, within thescar, develops in a ventral, strong and salient crestin C. alanrixi n. sp., as in every other observedChelodina, strong as in C. expansa and particular-ly wide. The crest is also developed in Emyduras.l. (for example in E. macquarrii), although lessdeveloped than in Chelodina expansa and dou-bled in some specimens, Pseudemydura (shallowrib) and South American chelids, such as manyspecies of Phrynops and Hydromedusa (narrow orthin, sharp or rounded in the scar). The characteris subdued (shallow with a short or thin crest) orabsent in many other species of Emydura s.l. andof Phrynops. In the Emydura group, instead of acrest of rib 9, there are often rugosities, forexample in Elseya novaeguineae and E. latister-num, or a triangular zone of sutural tubercles, as for example in specimens attributed, incollections, to Emydura australis. A zone oftubercles around the crested rib is present in theSouth American Chelus Duméril, 1806. In thepresent case, the scar and rib conform those ofC. expansa.

ScutesThe costals and vertebral 5 much overlap theperipherals and pygal as in Chelodina, dorsally(Figs 1B; 2; 10) particularly as in C. expansa(Fig. 10B); ventrally (Fig. 3), the marginals over-lap the peripherals more than in that species.Vertebrals 1 (at least in the preserved posteriorpart), 2, 3 (certainly, although lacking) and 4 arestrongly narrowed. Although the vertebrals areincomplete, the narrowing is shown by the closeproximity of the lateral vertebral border to thelateral neural border (a narrow pleural covered bythe vertebrals). Vertebral 5 is narrow anteriorlyand wide posteriorly. It is wider than the supra-

pygal, which it fully covers as well as covering apart of pleurals 8 and of peripherals 10, 11 andpygal. This particularly strong narrowing of thevertebrals from the posterior part of the first tothe anterior part of the fifth is derived and parti-cular in chelids to the relatively elongated extantspecies of Chelodina (shell moderately elongate toelongate), particularly C. oblonga and C. longicol-lis, although a regular narrowing of the series iscommon in all chelid forms, including allChelodina species. But in the extant C. expansa,with less narrowed vertebrals (Fig. 10B), and atleast C. siebenrocki, C. parkeri Rhodin &Mittermeier, 1976, C. rugosa, C. oblonga andC. longicollis, with more narrowed vertebrals, ver-tebral 5 is so much narrowed anteriorly that it isnarrower than the suprapygal (in most examinedspecimens), or as wide as the suprapygal onlyposterior to the suprapygal (at least some speci-mens of C. longicollis and C. oblonga). In thefossil suprapygal which is part of the specimensattributed to C. insculpta De Vis, 1897,vertebral 5 is also narrowed relatively to the plate.On the pleurals, which are also parts of those spe-cimens, the preserved parts of the vertebrals arealso narrowed. They are not as narrow as inC. alanrixi n. sp., C. longicollis and C. oblonga,but as in C. expansa for example (Fig. 10B). Inthe short rounded C. steindachneri, the vertebralsalso look narrow compared to the costals, but thecostals are widened, owing to the widening of theshell, thus giving a narrowed aspect to the verte-brals. In the other forms not showing narrowing,the vertebrals are, primitively, little differentiatedon the whole, although they tend to be narrowedfrom the anterior one posteriorly; sometimesthere are subdivisions of the second or of thefourth in a short and narrow supplementary scuteas in the other group of elongate forms. In theseforms that are not elongated as in C. alanrixin. sp. and unlike all the other fossil and extantspecies of Chelodina, the vertebral 5 is wider thanthe pygal, which is the primitive condition. Wethink therefore that, for the character of nar-rowed vertebrals, C. alanrixi n. sp. is also separatedfrom the group with rounded shells such asC. steindachneri and probably also from Redbank



Plains form 2. C. alanrixi n. sp. may be just at thebase of a group including extant Chelodina formswith vertebral 5 narrower, at least anteriorly, thanthe suprapygal, the character of narrowed verte-brals 2 to 4 being shared in common. If this cha-racter, of vertebral 5 narrowed relative to thesuprapygal, developed only once, then C. alanrixin. sp. is the sister group of the latter and thegroup with rounded shells such as C. steindachne-ri their common sister group. In this case, theshortening of the sulcus between the pectoral wasproduced twice, once in C. longicollis and once inthe C. steindachneri group (see Discussionbelow). But the character of vertebral 5 narrowrelative to the suprapygal may have developedseveral times and we lack too much of C. alanrixin. sp. (plastron, skull, neck) to detect the possiblehomoplasies and define exactly the phylogeneticrelationships of the fossil form.In chelids, it sometimes happens that instead ofcovering the peripherals and pygal, vertebral 5 isposteriorly reduced in length and marginals 12developed, at least medially, over the suprapygal.This happens in Emydura sp. aff. E. macquarriifrom the Oligo-Miocene of Tasmania (Warren1969a) as well as in some South American extantspecies of Phrynops and the Cretaceous chelidsfrom the Area Loma de la Lata and OchoHermanos (Broin & Fuente 1993; Lapparent deBroin & Fuente in prep). Sometimes also, margi-nals 12 meet vertebral 5 just at the pygal-supra-pygal suture, which is more like the primitivecondition in turtles. But the more frequent statein chelids is that of a moderate overlapping forthe peripheral border by the costo-vertebralscutes. C. alanrixi n. sp. is therefore well-devel-oped in this state, as is C. expansa. It differs, onthis point, from C. oblonga which has a relativelyshort posterior border (apomorphic) with a shortscute overlap, as compared to C. expansa. On theother hand, C. oblonga is much more elongateanteriorly (longer nuchal relative to shell length)than C. expansa and probably C. alanrixi n. sp. We note that vertebral 5 is partly longitudinallydivided anteriorly, in C. alanrixi n. sp.: this is anindividual variation sometimes present in speci-mens of all extant turtles.

DISCUSSION

Chelodina alanrixi n. sp., clearly pleurodiran asshown by the pelvis sutured to the shell, is aChelodina species because of the shape of theshell; its decoration; its posterior border, elongatebut not too much; its iliac scar morphology andextension; its narrowed vertebrals 2 to 4, as insome extant species of Chelodina.The genus Chelodina is well-defined, in extantspecies, principally on two excellent derived cha-racters that are not preserved here:1) on the anatomy of the skull, with a completedorsal skull fenestration, beginning from the lateralemargination and prolonged backwards, cutting thesupraoccipital-parietal contact with the squamosal;2) on the intergular scute, withdrawn backwardsfrom the epiplastral border, allowing the gularscutes to meet anteriorly to the intergular, or tonearly meet in the holotype of Chelodina intergu-laris Fry, 1915 (a deformed C. rugosa fide Thom-son pers. comm.) (Wermuth & Mertens 1961;Goode 1967). Posteriorly, the enlarged intergularcompletely separates the humeral scutes and apart of the pectorals. For this character, the morederived forms are the shorter forms (includingthe rounded C. steindachneri) where theintergular is more backwards prolonged and thesuture between the pectorals shorter, but C. lon-gicollis, a relatively elongated form judging by theskull (see below) and without a widened carapace,also approximates them (short hyoplastral sutureand interpectoral sulcus). For the intergular posi-tion, the less derived are the elongated-narrowedforms and among them the C. siebenrocki-rugosagroup, including C. intergularis, and C. oblonga.A short skull is the primitive condition and anelongation of the palate, correlated with a flatten-ing of the skull, is produced in the elongated-narrowed forms. The elongation can bemeasured by the ratio of the lateral ventral lengthof the pterygoid, between its suture with thejugal and the maxillary and its suture with thequadrate, on the skull width, at the quadrateventral border below the tympanic meatus. Theratio is the shortest in Pseudemydura. Then, theratio elevates a little in the Emydura group.According to the figures of the authors, the



forms of Chelodina with a medium-sized andshort, more or less rounded carapace, includingC. reimanni, C. pritchardi and C. mccordi, havethe same proportions for the skull characters: allof them have the lowest percentage in Chelodina,which in part (C. steindachneri) covers that ofsome Emydura s.l. species. Their higher percen-tage (C. novaeguineae) is below that of C. longi-collis and that of the other forms with amoderately elongated or clearly elongated shell:within this group, the skull elongation is visuallynoticeable from C. longicollis and it is maximumin C. expansa. A less transverse position of thetrochlear pterygoid processes is partly correlatedwith the skull elongation. The neck is also longerin the longer skull forms than in those with shortskull forms. There are overlaps between thespecies. The living species of Chelodina are often classi-fied in two groups, following a dichotomous sys-tem which is very useful, although fully phenetic:it is principally based on the length of the plas-tron relative to the width (plastral length general-ly about one time and a half maximum width,rarely exceeding one time and three-fourth themaximum plastral width, or usually greater than1.9 time the maximum width of plastron (Cogger1992; Goode 1967). This system does not takeinto account: 1) the way the various parts of theplastron (anterior lobe or all the posterior lobe orxiphiplastral points only or all the plastron as awhole) are widened and enlarged, relative to theprimitive chelid narrow short state with narrowxiphiplastral points; 2) the way the plastron iswidened, relative to the way the shell is elongatedor rounded (widened). Also are considered othercharacters such as the skull (broad or narrow), thecontact between the pectorals (short in formswith broad plastron or long in forms with longplastron), some other characters (barbels, headand neck skin surface, odour, etc.) and some rela-tive proportions which are variable and withoverlap between the two groups. The primitiveand the derived states and the intergradations arenot taken into account. The plastral size and theevolution of the intergular posteriorly do notcoincide with the other characters of the skull

(elongation and flattening, position of the tro-chlear pterygoid processes, etc.), neck elongation,changes in plastral proportions, neural reduction,border proportions, vertebrals narrowing (seeabove), etc.The characters of the two phenetic groups do notcoincide with those used here to distinguish thefossil species. For example, in the phenetic dicho-tomous system, C. longicollis is placed by theauthors with the short forms of the type ofC. steindachneri and C. novaeguineae. However, ithas a relatively elongate skull as C. siebenrocki,narrowed vertebrals as C. oblonga, vertebral 5narrower than suprapygal as the large C. expansaand as the long forms, and it has not a widenedor narrowed-elongated shell although it has awidened plastron. Cladograms of Chelodina spe-cies are given (Rhodin 1994a, b) supporting thephenetic system, but they are not verifiable orrefutable because they are given without thematrix and list of the characters. Other phyloge-netic studies are based on electrophoretic data oron mitochondrial and nuclear gene sequencevariation (Georges & Adams 1992, 1996;Georges et al. 1999), not useful in our study offossils (see also White 1997). Their results, notincluding fossils, do not present the evolution inall the forms from Triassic to present times. Theyare useful overall in separating paraphyletic taxaat the generic level, according with the osteologi-cal results: for example Elseya. As far as Chelodinais concerned, these analysis correspond togetherand with the phenetic system, grouping speciesmostly on synplesiomorphic charaters, but notwith our observations: in one analysis, C. longi-collis is placed with C. steindachneri and C. novae-guineae (two rounded short forms), withC. oblonga as sister group, and the whole withC. rugosa and C. expansa as outgroup (Georges &Adams 1992). In another paper, C. oblonga andC. longicollis have C. rugosa as outgroup, C. stein-dachneri not being integrated (Georges et al.1999). Thomson (pers. comm.) supports anindependent acquisition of skull lenghtening anda possible reversion to a short skull in variousextant species and the separation in the twoChelodina groups of the authors, A and B, on



osteological characters. It will be interesting tosee if the characters shared by each group aresynapomorphic or synplesiomorphic, if we candetect the homoplasies and conciliate the contra-dictions with the present statements.

In fact, the distribution of the derived characterspreserved here appears as a mosaic type. In theabsence of the skull, neck and plastron, we can-not establish a cladogram to show the phyleticposition of C. alanrixi n. sp.



TABLE 2. — Comparative elements of five specimens (1 to 5) from Redbank Plains, Queensland, Queensland Museum. Abbreviations:app., approximately; n, neural; part 7, 8, posterior part of pleural 7, pleural 8; per. 10 L/w, peripheral 10, anterior length on externalwidth; PL, posterior lobe of plastron; PL w/L, plastral posterior lobe, width at abdomino-femoral sulcus on maximal length; py,pygal; spp, suprapygal; V, vertebral scute.

Posterior Iliac suture under

Forms, taxa from shell shape pleurals

Redbank Plains Decoration Neural and spp; Vertebralsnumber; pubis,continuous ischiadic scars

1: Chelodina alanrixin. sp., (sp. a)(QM F18344), cara-pace: width c. 30 cm;length c. 41 cm;per. 10 L/w = c. 94%

2: Chelodina sp. b(QM F18214), cara-pace: width c. 14 cm;length c. 16,5 cm; per.10 L/w = 95%

3: Chelodina sp. c(QM F18216-18215):carapace lengthc. 25 cm;upwardly-curlednarrow bridgeperipherals as invarious Chelodina

4: Chelodina sp. c?(QM F18212)plastral lengthc. 18 cm?, carapacelength c. 22 cm?PL w/L = 91.95% (asin Emydura s.l., < toextant Chelodina);preserved part PL= shape as in someEmydura s.l. and as insome Chelodina

5: Emydura s.l. sp. a(QM F31697), cara-pace: widthc. 15.5 cm; lengthc. 20 cm; PL w/L =c. 94 to 100%

Strong dorsal; verysmall polygons, elong-ate: transversally (lateralparts), longitudinally(medial parts) and obli-quely (posteriorly)

Strong dorsal; verysmall polygons,at least elongatetransversally on lateralparts

Strong dorsal; smallpolygons regularlydistributed, as inChelodina

Strong ventral; plastralgranulate polygonsregularly distributed,particularly as inE. (Elseya) dentata,longitudinally elongateon posterior hypoplas-tron and on hypo-xiphi-plastral suture areas;polygons very small;dorsal polygons as inChelodina

Weak dorsal decoration(some weak dichoto-mous sulci); plastralweak polygons

Slightly point-ed in openrounded V.n1 to partialn8; yes,without sppcontact

Rounded.?, withoutspp contact

?

?

?

?

Rounded.0 dorsal (n 6-8 preservedventrally); no

V1?, V2 to V4 verynarrow << V5 > spp;V5 long on py

V1-V3?, V4 V5 narrow, V5 app.= spp; V5 long on py

?

?

V1-V3?, wide (angulate lateralborders) V4 < wide V5 >>

Trapezoid, part 7, 8,wide good part spp;strong wide rib 9; ?

? ?

?Pubis scar diamond-oval shaped, ischiadicscar posteriorlyrounded as inChelodina

?Pubic scar oval as insome Emydura s.l., atleast E. (Elseya) latis-ternum and E. (Elseya)novaeguineae

Trapezoid-roundedtriangle, part 7, 8,rounded part spp;rugosities on rib 9; ?

We just can take the obvious characters inC. alanrixi n. sp., which are principally those ofthe evolutionary states of neurals, of width of ver-tebrals 2-4 and of anterior width of vertebral 5.The combination of these characters shows thatthe species is new, compared to the fossil andliving species, and that it is rather primitive.The diagnosis shows it is similar (same derivedstate of characters) to C. expansa (see Fig. 10) byits large size, the posterior slightly pointed flat-tened border (overall in males), the strength of theiliac scar crest and the posterior plate proportionsand scute covering, all characters in which it par-ticularly differs from C. oblonga. Its pecularitiesare never found as individual variations in extantC. expansa . But it is more primitive thanC. expansa, C. longicollis and the relatively elonga-ted and elongated-narrowed living forms by thewidth of the vertebral 5, not anteriorly reduced,differing there as well as from the fossil suprapy-gal attributed to C. insculpta.Relative to C. expansa, it differs also by the pre-sence of a prolonged neural series. In this charac-ter, it is similar to C. oblonga, that retains one toseven neurals (although the first one is incom-plete in front, when present), but this is a primitivecharacter not allowing a privileged phyletic rela-tion between them. On the other hand, the fossilform 1 shares with C. oblonga a very derived cha-racter, the higher degree of narrowing of verte-brals 2 to 4. However, it lacks the shortenedposterior border of C. oblonga and the vertebralsare also often much narrowed in C. longicollis,which lacks an elongated-narrowed shell: narrow-ing of the vertebrals, present in a higher degreein C. alanrixi n. sp., is not linked to the carapaceelongation and modification of the posteriorborder.The dorsal elements are sufficient to separate thisspecies from C. insculpta De Vis, 1897. In theabsence of a preserved plastron for the RedbankPlains form 1, we cannot analyse its differencesfrom the plastron of the living and fossil species.In the former (and composite) species, the ante-rior and posterior preserved plastral parts areconsistent with the belonging to only one speciesof a single age, owing to the decoration and the

proportions of the elements. The preserved partof the anterior plastron is more similar to that ofC. longicollis in the relative distances betweensutures and scutes than to the elongated forms; inparticular, the suture between the two hyoplastraand the sulcus between the pectoral scutes arerelatively short, compared to the elongated formswith a long suture, being closer to the roundedforms with a short suture, but the plastral ante-rior lobe is much narrower than in C. longicollis.The posterior part is also much less widened,anteriorly and posteriorly, so closer to the primi-tive chelid state: it is still narrow at the hypoplas-tra and anterior part of xiphiplastra and lesswidened at the posterior part of the xiphiplastrabelow the anal scutes. It is different from theextant species although most of them have stillnarrowed anals.In summary, the Redbank Plains form 1, C. alan-rixi n. sp., is therefore a new species primitiverelative to extant and fossil Chelodina species,although much derived in having the vertebralsnarrowing as in the moderately elongated andvery elongated forms. It is different from therounded species, including the following



FIG. 4. — Chelodina sp. b, form 2, Redbank Plains, Queensland,Eocene (QM F18214), right lateral and posterior part of the shell,impression of the external face. Scale bar: 2 cm.

Redbank Plains form 2, and from the extant specieswithout vertebrals narrowing. It differs also fromthe Redbank Plains form 3 by its elongate andsmaller (relatively) polygons, its larger size and thepresumed absence of an upwardly-curled border.

Chelodina sp. b

DESCRIPTION

Material (Figs 4; 5; Table 2) (Rix 1991: fig. 2A)Redbank Plains form 2 is represented by the spe-cimen QM F18214. It is an external impressionof a fragmentary carapace, of the right lateral andposterior parts. It includes the impression of thelateral border from the peripheral 4, the impres-sion of the right peripherals 5 (a part) to periphe-ral 11, of the pygal and of a part of the leftperipheral 11, of the lateroposterior part of thepleurals 3-8 and a part of the suprapygal.

Measurements (in cm)Oblique anterior preserved border: c. 13.8.Width at the peripherals 5: 14.Estimated medial length: c. 16.5.Maximal suprapygal width: 3.6.Maximal vertebral 5 width: 3.6.Peripheral 10 anterior length on external width:1.9/2 = 95%.

DecorationThe decoration is similar to that of Chelodinaalanrixi n. sp. except that the size of the polygonsis much reduced, in proportion with the muchreduced carapace size. The polygons are c. 0.5-1 mm wide and 0.1-4 mm long. The polygonsare very well-marked and uniformly distributedon the shell part preserved as in all the Chelodinaspecies, including C. alanrixi n. sp. as well as therounded extant form C. steindachneri. They arevery elongate on the lateral extremities of thepleurals and on the posterior extremity of thesuprapygal, at the boundary with the peripheralsand the pygal, more elongate there than inC. alanrixi n. sp. and in the extant species. Thepolygons are slightly smaller than in the C. stein-dachneri and C. novaeguineae (they are notknown in the relatively short and medium sizedrecently described other extant species). As inChelodina, the polygons of the peripherals areelongate in the direction of the lateral border ofthe carapace. The polygons of the suprapygal areequivalent in size to those of the suprapygal attri-buted to C. insculpta De Vis, 1897 (pl. V, H) butthose are not drawn obliquely oriented and notposteriorly elongate. However, the other frag-ments attributed to this species have coarser poly-gons, as in the extant species of Chelodina. Asshown above (Table 1), these fragments, includ-ing the lectotype selected by Gaffney (1981),are not precise as to their origin and age: Plio-Pleistocene of Darling Downs and WarburtonRiver and Eocene of Eight Mile Plains. Theycould therefore include a specimen equivalent inage to a Redbank Plains form. Thomson (pers.comm.) thinks that all the figured specimens arefrom Darling Downs.

Shell shapeOf the parts preserved, the width of the posteriorpreserved part and the shortness of the preservedpleurals, make it possible to reconstruct a round-ed oval carapace, like that of a rounded form ofChelodina such as the extant C. steindachneriSiebenrock, 1914. Figure 5 shows the reconstructionof the posterior part of the carapace reconstructingthe left side symmetrical to the preserved right side.



FIG. 5. — Chelodina sp. b, form 2, Redbank Plains, Queensland,Eocene (QM F18214), reconstruction of the lateroposterior partof the shell. Abbreviations: C4, costal scute 4; py, pygal; spp,suprapygal; V4, V5, vertebrals scutes 4 and 5. Scale bar: 5 cm.

V4

C4

V5py

spp

The shell, with well-sutured plates, is that of ayoung adult with still uncovered rib extremitiesor of an adult of a species keeping free lateral ribextremities in the peripherals, visible dorsally, asin various extant chelid species and in particularas in many Chelodina. The shell is estimated tohave been rather rounded, the width relative tothe presumed length being estimated as c. 85%.This percentage is that of C. steindachneriSiebenrock, 1914 (up to 86.79%, see Table 3).The rounded posterior border of the pleural discis comparable to that of C. steindachneri andC. novaeguineae, not as narrow as in most of theother extant species and not cordiform as inPseudemydura. The posterior border of the cara-pace is short, rounded and not slightly mediallypointed, as it is in extant C. expansa and inC. alanrixi n. sp. (and still more pointed inC. longicollis and C. mccordi). As in C. alanrixin. sp., C. expansa and some other species such asC. steindachneri and C. pritchardi, it is not raisedat the pygal, convex from side to side, as in theextant C. longicollis and C. mccordi. It is not so asmarkedly convex, inwardly recurved and ventral-ly narrowed as in Pseudemydura. It is not elonga-ted and expanded as in the Emydura group.

Laterally, nothing indicates the presence of thebeginning of an upwardly-curled border as inC. sp. c, C. longicollis and in some otherChelodina species and as in Pseudemydura.

Dermal bonesThe length of the preserved pleurals is short com-pared to the lateral pleural borders in contactwith the peripherals. This allows the reconstruc-tion of a rounded form as C. steindachneri. Thefree rib extremities are clearly visible in theimpression of the external dorsal view, more thanin most extant adult forms. It might therefore bea sub-adult of a slightly larger adult form. Theplates of the border are not very elongated. Thepygal and peripherals 11 and 9 are as wide exter-nally as long anteriorly, the peripheral 10 is widerexternally than long and the peripherals 8 andanterior (preserved to peripheral 5) have theirexternal border progressively elongated relative tothe shortened anterior and posterior borders. Theratio length/width of the peripheral 10 is 95%,approximately as in C. alanrixi n. sp. As seen above,it is a low ratio in Chelodina, just higher than inC. oblonga and closer to that of C. steindachneriand C. expansa, as well as that of Pseudemydura,



TABLE 3. — Comparative carapace ratio of width to length in the carapace of some living Chelodina.

Taxon Carapace length % carapace width/length

C. alanrixi n. sp. c. 40-41 cm (estimated) 73 to 75?C. expansa up to 42.3 cm 78 (MNHN AC 1914-178);

70.5 to 76.12 (Goode 1967)C. longicollis up to 32 cm 71.21 (MNHN AC 1911-181);

77.87 (MNHN AC A 5190)C. reimanni up to 20.6 cm 68.93 to 76.66 (Philippen & Grossmann 1990)C. pritchardi 22.8 cm 72.83 to 81.36 (Rhodin1994a)C. mccordi 21.3 cm 76.05 to 79.35 (Rhodin 1994b)

(young 73.36)C. novaeguineae up to 18 cm 77.77 (BMNH 46.1.22.36);

74.73 to 78.10 (Goode 1967)C. steindachneri up to 22 cm 80.24 (WA R 29375);

84.92 (WA R 113100);84.61 (WA R 113101);up to 86.79 (Goode 1967)

C. rugosa 20.2 cm 75.74 (MNHN H 1983-378)C. siebenrocki up to 27.5 cm 67.27 to 75.49 (Goode 1967)C. oblonga up to 28 cm 60.97 (UWA); 66.66 (BMNH 64.12. 22.6);

67.34 (WA R 29382);63.14 to 72.34 (Goode 1967)

and far from the higher ratios of the Emyduragroup. Also, it indicates a moderate expansion ofthe posterior border, distinct from the tendencydeveloped in the Emydura group. The suprapygal is pentagonal, more or less point-ed anteriorly (missing in part).

ScutesThe vertebral 5 and costals 4 overlap the peripheralsand pygal less than in C. alanrixi n. sp., C. expansaand C. longicollis, as in C. steindachneri and morethan in C. oblonga. More anteriorly, the sulcus ofthe costal 3-marginals remains a little external to theperipheral-pleural suture and then is nearly unitedwith it. We do not know how it was in C. alanrixin. sp. In extant Chelodina, the osteology of which isknown, either all the costals remain overlapping theperipherals laterally (C. expansa) or the costal 2alone is united with the suture (C. longicollis) or nearlyunited to the suture (C. steindachneri, C. oblonga).It therefore may have a specific value. In theRedbank Plains form 2, the morphological stageis closer to that of the forms with a roundedposterior border than to that of C. expansa,C. longicollis and other elongate forms.Part of the medial carapace, anterior to the supra-pygal, is missing. We know nothing about pre-sence of neurals and width of vertebrals, exceptthat the vertebral 5 is just as wide as the maxi-mum width of the suprapygal. It is therefore nar-rower than in C. alanrixi n. sp. and C. steindachneri(not known in C. novaeguineae but probablywide as in C. steindachneri). But it is still widerthan in forms without a widened shell and withnarrowed vertebral 5, including C. longicollis,C. expansa and C. oblonga.

DISCUSSION

The posterior part of carapace QM F18214shows the decoration of Chelodina. The shape ofthe preserved part agrees with Chelodina and notwith Emydura s.l. and Pseudemydura.Within Chelodina, the specimen better agreeswith the rounded form C. steindachneri but alsowith some extant forms without a pointed andmedially raised posterior border (the primitivecondition) such as C. reimanni and C. novaeguineae.

It differs from C. alanrixi n. sp. in the relativelysmaller size of the polygons, owing to the smallersize of the carapace. The size of the polygon isalso smaller than in another fragment of turtlefrom Redbank Plains, studied below and attribut-ed also to Chelodina, undefined species, from acarapace slightly larger than the Redbank Plainsform 2. The size of the polygons is also smallerthan in the dorsal shell of extant species (smallerpolygons exist in plastral part of extant speciessuch as C. steindachneri). It is similar to that of thesuprapygal referred to C. insculpta De Vis, 1897.But this has a clearly narrowed vertebral 5, narrowerthan the suprapygal, as in the extant C. longicollis,C. expansa and the elongated species. In return,in this character, the Redbank Plains form 2 isless derived, intermediate between them and theshort C. steindachneri which has a vertebral 5wider and even much wider (enlarged in somespecimens) than the suprapygal and C. alanrixin. sp.: the vertebral 5 is here slightly narrowerand shortest on the external border plates.It differs also from C. alanrixi n. sp. by the morerounded shape of the carapace with relativelyshortest pleurals, the smaller size of the carapaceand of the polygons.It seems to differ also from the Redbank Plainsform 3, undefined sp. of Chelodina. This is larger(maybe because an older individual) with relati-vely larger dorsal polygons. Furthermore, the lat-ter has a recurved lateral border, as in manyextant species, which does not seems to be pre-sent here.In summary, it is probable that it belongs to theC. steindachneri lineage and to a new species, butthe elements are insufficient to define it.Furthermore, as long as the osteology of all theextant species is not known, it is not possible tosatisfactorily address this question.

Chelodina sp. c

DESCRIPTION

Material (Table 2)The Redbank Plains form 3 consists of specimensQM F18216 and 18215, the impression of a



fragment of carapace, comprising some dislocatedplates in which we recognize three right bridgeperipherals, four or five fragments of pleurals anda plastral bridge element, with the fragmentaryleft pubis and ischium.

Measurements (in cm)Right peripheral 7: posterior ventral width: 2.2;lateral length: 2.6; anterior ventral width: 1.5.Right peripheral 6: posterior ventral width: 1.2;lateral length: 2.6; anterior ventral width: 0.9.Right peripheral 5: posterior dorsal width: 1.5;lateral length: 2.5; anterior dorsal width: 1.5.Pleurals anteroposterior length: 2.2 to 2.4.Length of the bridge: 5.2 (and c. 2 mm more ofhyoplastron hidden under the hypoplastron).The elements belonged to a carapace of 24 or25 cm long, estimated by comparison withC. longicollis.

DecorationSize of the polygons (approximate), on pleurals:3-4 over 1-1.5 mm, on peripherals: 1 over 1 mm,on plastral bridge part: 0.5 over 1 mm.The decoration is made of small well-markedpolygons (strong decoration), most of themrounded and well-distributed, as in Chelodinaand Pseudemydura. The carapace polygons aresimilar to those of the shell of C. oblonga andC. longicollis, for example within the extant spe-cies, and to those of the figured specimens attri-buted to C. insculpta. But the polygons aresmaller for a shell of equivalent size to that ofC. longicollis, C. oblonga and C. insculpta,although larger than in the two other species ofChelodina from Redbank Plains. The plastralbridge element bears still much smaller polygonsthan the carapace, arranged in transversal elong-ate lines and in radiate lines. The carapace deco-ration is also similar to that of Pseudemydura, butthe plastral polygons are smaller than in thisextant genus and the other elements prevent theattribution to this genus.

Dermal bones of the carapaceThe preserved right peripherals 7 and 6 are seenin ventral and medial views. The seventh is the

last of the bridge and, then, less open than thesixth. Besides, the right peripheral 5 is shownonly in dorsal view, associated with a fragment ofcorresponding pleural 3. Two superposed frag-ments of even pleurals (with the sulcus betweentwo costals) are preserved besides.The plates have the morphology of the corres-ponding plates in the extant C. longicollis. Theexternal dorsal border of the fifth peripheral isnarrow and upwardly-curled. In medial view ofthe peripherals 7 and 6, the hole for the free rib iswell-visible and the medial width (between dorsaland ventral borders of the plate) is equivalent tothat of C. longicollis. But their ventral width isslightly less than that of the corresponding platesin C. longicollis: the peripheral border was lessexpanded. It is also nearly similar to that ofC. oblonga, but less narrowed and more curled.

PlastronA small part is seen under the peripherals. Itconsists of the bridge part of the hyoplastron andhypoplastron and does not show any determinantcharacters except its very fine and granulate unu-sual decoration, as in the following specimen,form 4, from Redbank Plains.

PelvisThe left pubis is seen in inferoposterior view. Thepubic ventral suture with the xiphiplastron is dia-mond shaped, nearly oval: anterior and posteriorsharp angle, with rounded lateral borders. Thetype of pelvic scar on xiphiplastra has not beenobserved in every Australian chelid, owing to lackof the preparation of the material. But this typeof pubic scar has been seen in Chelodina oblonga.It is different from that of C. expansa, long, nar-row posteriorly and wide anteriorly, from that ofC. longicollis, short, triangular, wide anteriorly,and from that of C. steindachneri, short, oval andnearly round. In the Emydura group, some spe-cies have an oval shaped suture, very similar butwithout extreme sharp angles. In Pseudemydura,the suture is similar to that of C. longicollis, ashort rounded-triangle, wide anteriorly. The ischium is represented by the ventral part, ininner and ventral view. The ventral suture for the



xiphiplastron is incomplete medially but fortuna-tely complete posterolaterally: its posterior extre-mity is well-rounded. This is typical of Chelodina,as seen in the C. alanrixi n. sp. section in itsdiffering from the other chelid forms with anangulate posterior part (primitive condition). Inthe Pleistocene example of Chelodina, fig. 18A ofGaffney 1981, given above, the rounded scar iscloser to the lateroposterior border of the platethan in Emydura s.l. If the scar is rounded poste-riorly in all the examined species of Chelodina, itsposition varies. The scar is still closer to the latero-posterior border of the plate in C. oblonga(narrowed form), farther laterally and posteriorlyin C. longicollis (form with enlarged xiphiplastraand a reduced anal notch) and farther posteriorlyin C. steindachneri (narrow xiphiplastra but shortanal notch). In the Pleistocene form, the scar issituated as in C. expansa, within the Chelodinaspecies, but we do not know its position in theRedbank Plains form 3.

DISCUSSION

This specimen belongs clearly to Chelodina bythe set of obvious characters:– the complete cover of polygons on the dorsalshell. When there are polygons on the dorsalcarapace in Emydura s.l., there are also ridges orgranulations or smooth areas: the polygons arenot well-marked and well-distributed over all thedorsal shell, a difference from the plastron whichhas often a cover of well distributed polygons(although it is probable that the primitiveEmydura group members had a more polygonalcarapace);– the curled peripherals: there is a slight upwardly-curled border in some Emydura s.l. such asE. macquarrii, but the width of the bridge peri-pherals is much larger and the border is not socurled;– the well-rounded posterior border of the ischia-dic suture with the xiphiplastron.The two first characters are also shared byPseudemydura, the first one being a primitive char-acter in chelids, the second a derived characterbut homoplastic in turtles. The third is autapo-morphic in the observed material of Chelodina,

and the set is diagnostic of the genus. But it isimpossible to define the species. It is differentfrom C. alanrixi n. sp., which is much larger andhas relatively small (owing to the larger size) andnarrower polygons. In the latter, the bridge peri-pherals are not preserved so that we do not knowif they were upwardly-curled. But the relativelywide and flat posterior border does not indicatethat the peripherals had to become recurved atthe bridge; they had to be flat or scarcely recurvedas in C. expansa. The undefined species is proba-bly also different from the form 2, smaller withsmaller polygons and probably also withoutupwardly-curled border. It does not seem a round-ed species of the lineage of C. steindachneri. Itmight better belong to an elongated species (suchas in C. oblonga or C. siebenrocki-rugosa lineages)or to a moderately elongated species (such as inC. longicollis lineage).

Chelodina sp. c?

Emydura s.l. sp. ? Possible synonymy.

DESCRIPTION

Material (Fig. 6) (Rix 1991: fig. 2B)Redbank Plains form 4 is represented by the spe-cimen QM F18212. It consists of a broken no-dule with the impression of half of the plastron,posterior part, without the bridge, with animpression (natural mold) of a part of the rightpelvis in external view and parts of two or threeright posterior peripheral plates.

Measurements (in cm)Maximal length and width of the fragment: 13.6and 10.4.Maximal length and width of the preserved partof the plastron: 12.5 and 7.8.Maximal length of the half posterior plastron(from hyo-hypoplastral suture): 10.5.Maximum length of posterior lobe (from abdo-mino-femoral sulcus): 8.7.Width of posterior lobe at abdomino-femoralsuture: c. 8.Ratio of width to estimated length of posteriorplastral lobe: c. 92%.



Width at the femoro-anal sulcus: 5.5.Preserved height of the pelvis (dorsal part ofilium incomplete): 3.6.Anal notch, width and length: 3.4 and 1.

DecorationAll the preserved part of the plastron (Fig. 6D, E)is covered with small polygons, elevated, well-marked (strong), well-separated, most of themrounded, c. 1 ✕ 1 mm wide, giving a granulateappearance to the positive (mold) of the speci-

men: but the fossil impression of the fig. 2B ofRix 1991, which is reversed, shows small pitsseparated by fine crests. As indicated above, acover of polygons is present in the plastron ofChelodina and Pseudemydura as in variousEmydura s.l. The polygons are arranged in lines,oriented from a center at the lateral border of theabdomino-femoral sulcus and quite longitudinal-ly elongate in the hypo-xiphiplastral suture area.The plastral polygons (Fig. 6E) are relativelysmaller than in Pseudemydura. In Chelodina, we



FIG. 6. — A, plastron of Elseya dentata (BMNH 76-5-19-77); B, plastron of Chelodina oblonga (BMNH 64-12-22-6), ventral views;C-E, Chelodina sp. c?, Redbank Plains, Queensland, Eocene (QM F18212), positive of the posterior mid-part of plastron, partial rightpelvis and small part of shell; C, enlargement of the shell part, showing the polygons similar to those of Chelodina; D, the specimen,ventral view; E, enlargement of a plastral part showing the small granulate polygons; F, posterior mid-part of the plastron, super-posed to that of Chelodina oblonga, with reconstruction of the inguinal notch. Abbreviations: a, left, as in Elseya; b, right, as inChelodina. Scale bars: A, B, D, 2 cm; C, E, 1 cm.

A

C E

D

BF

a

b

have seen relatively as small polygons in the plas-tron of C. steindachneri and in the preserved partof bridge of form 3, Chelodina sp. c. But, as seenabove, the polygons are not as longitudinallyelongate in those two genera and this is rather acharacter of the Emydura group. In the latter, asimilar decoration has been observed in Elseyadentata (BMNH 76-5-19-77), although the poly-gons are slightly smaller in the fossil, for a similarplastral size (Fig. 6A). The fragmentary peripherals have also well-marked,small and granulate polygons. One of them alsoshows small polygons (Fig. 6C), high as inChelodina and particularly as in Chelodina sp. c.They are also similar to the polygons of the plas-tron of C. oblonga (Fig. 6B) and we considerthem as apomorphic for Chelodina.

Plastron (Fig. 6D, E)The plastron impression has a central rhomboidfontanelle, as observed in juveniles, for examplein Elseya latisternum (BMNH 71-9-25-8). It ispreserved from the pectoro-abdominal sulcus,anteriorly, to the anal notch, posteriorly. Theexact shape and proportions of the posterior lobeare not possible to determine. The fragment iscut short, laterally, so that we do not see wherethe inguinal notch was positioned nor do weknow how long the bridge was. If the inguinalnotch was situated at the lateral extremity of theabdomino-femoral sulcus (Fig. 6F, a), it was afragment of Emydura s.l. as in Fig. 6A. In the twoRedbank Plains forms attributed to the Emyduragroup, the sulcus finishes in the bottom of theinguinal notch and the bridge was relatively long,as in the other Emydura species. But if the bridgewas shortened, the abdomino-femoral sulcus wouldnot end in the bottom of the inguinal notch, butbackwards on the border of the lobe (Fig. 6F, b)and the fragment would belong to a Chelodinaspecies as in Fig. 6B. The posterior lobe is elongate with proportionsknown in Australian chelids in the Emyduragroup. The percentage ratio of width to length ofthe posterior lobe (measured from the extremityof the abdomino-femoral sulcus) is c. 92%, whichconforms to the Emydura group, measuring bet-

ween 84.69 (Rheodytes leucops) and 97 to 103%(E. macquarrii) as seen above in the study of theEmydura s.l. sp. a: the ratios are higher inPseudemydura (141%) and Chelodina (103 to138%) which have relatively shorter posteriorlobes. In Pseudemydura, the plastral lobe is shortand much rounded with a very small and narrowanal notch. It is very different from the lobe ofthe Redbank Plains forms 5 and 6. Here, as inEmydura s.l. sp. a, form 5, the two borders of theposterior lobe clearly converge, from the bottomof the inguinal notch, at the abdomino-femoralsulcus, towards the xiphiplastral extremities in astraight line, without strong narrowing at thefemoro-anal sulcus. Just a small indentation for aslight posterior anal narrowing is noticeable atthis sulcus. The anal notch is very widely round-ed and short, as in most of species of Emyduras.l., except some forms such as Elseya latisternumand E. novaeguineae which have a less roundedanal notch. But this shape of the posterior lobe isalso similar to that of C. oblonga (Fig. 6B) with itsslightly convergent straight lateral borders and awide and short anal notch. The anal notch of thefossil is relatively shorter than in Emydura s.l. butlonger than in C. oblonga, as shown in theFig. 6E. The percentage ratio “width/length ofthe posterior lobe” is elevated as in someEmydura s.l., known in E. macquarrii, but notdifferent from the lower one in Chelodina, inC. oblonga (103.44%). C. oblonga is the moreelongated species of Chelodina, with the relativelymore elongate posterior lobe.

Right pelvisIt is visible in external view, the inferior partbeing anteriorly positioned lateral to the plastron.The upper part of the ilium is missing. The aceta-bulum is slightly posteriorly dilated as in most ofadult chelids. Anteriorly, the posterior part of theventral suture of the pubis with the xiphiplastronis preserved: it is oval but apparently without asharp posterior angle, different from the speci-men of Chelodina sp. c described above. The pro-blem is that this extremity of the pubic scar maybe eroded. Such an oval suture and xiphiplastralcorresponding scar, primitive in its evolutionary



stage, is known in some specimens of theEmydura group such as Elseya latisternum andE. novaeguineae. It differs from that known inone specimen of Emydura macquarrii where it isnearly rectangular with a sharp anterior angle,and of one specimen of Elseya dentata where it isvery narrow. As in Chelodina there are differ-ences, unfortunately not studied at the specific orgroup of species level. No Chelodina and noPseudemydura are known with this oval morpho-logy but it is known in the Emydura group. Theventral face of the ischium is hidden below thexiphiplastron.

DISCUSSION

It is better to attribute the specimen of theRedbank Plains form 4 to Chelodina sp. c than toEmydura s.l., owing to the granulate plastraldecoration and polygonal dorsal decoration thatis exactly similar to those of the form 4. Thesmall size of the polygons better conforms withthose of Chelodina, in the context of the RedbankPlains Eocene forms and, in particular, the apo-morphic decoration of the preserved peripheralbone is consistent with that of Chelodina andnot with the Emydura group. But the extantElseya dentata has a similar granulate plastraldecoration and the proportions of the posteriorlobe are consistent with those of the Emyduragroup. The oval pubic scar, if correctly preserved,could better be consistent with attribution tothe Emydura group, as it is known at present.But the granulate decoration of oriented smallpolygons and the oval pubic ventral suturemay be primitive for both groups. In the absenceof the inguinal notch bottom, we cannot becertain.

Emydura Bonaparte, 1836 s.l.

Emydura s.l. sp. a

DESCRIPTION

Material (Figs 7-9C, D; Table 2)The single specimen of the Redbank Plainsform 5 (QM F31697) consists of a broken nodule

showing two parts of an incomplete carapace: theexternal impression of the scutes and plates of thepartial left lateral border and posterior border ofthe pleural disc and a part of the peripherals(Figs 8; 9D); the internal cast showing theimpression of the ventral part of the plates ofthe pleural disc, at the anterior border in anoblique line, from left side at the pleural 2 toright side at the pleural 3 to 5 (Figs 7; 8C). Theanterior part of the pleural disc is hidden by theimpression of the external part of the partial lefthalf plastron.

Measurements (in cm)Preserved length and width of the internal cast(i.e. approximately of the pleural disc): 17.5 and15.5.Presumed approximate length and width of thecarapace: 20 and 15.8.Ratio of width to estimated length of posteriorplastral lobe: 6.6/6-7, percentage ratio c. 94-100%.



FIG. 7. — Emydura s.l. sp. a, form 4, Redbank Plains,Queensland, Eocene (QM F31697), internal cast of the carapace,anteriorly covered by the external impression of the left latero-posterior part of the plastron. Abbreviations: an.n, reconstruc-tion of the anal notch; hyo, partial hyoplastron; hypo ,hypoplastron; il, iliac scar; n, ventrally preserved neural; per. 9,partial peripheral 9; pl7, pleural 7; spp, partial suprapygal; Xi,partial xiphiplastron. Scale bar: 5 cm.

hyo

Xi

an.n

pl7sppil

n

per. 9

hypo



DecorationThe external impression shows only a very weakdecoration of some shallow, thin and short sulci,some of them dichotomous. A small part of theventral decoration of the right marginal scutes 9and 10 is preserved on the cast of the fragmentaryperipherals 9 and 10: some small dichotomoussulci, shorter and closer together than in the pleu-rals, are also visible. The decoration could be slight-ly different at the level of the missing vertebrals.The impression of the plastron shows a strongerdecoration of rather large polygons, not elevated(weakly marked), elongate, oriented from a cen-ter near the inguinal notch, longitudinally on theposterior lobe and radially forward on the ante-rior hypoplastral part. Below the preserved femo-ral scute, the polygons are 7-5 mm long on4-1 mm wide.Such an attenuated decoration of the carapace isoften seen in the Emydura group, for example inElseya latisternum and in young E. novaeguineae.In other forms, the carapace may be covered byirregular polygons, not as well-formed and as clo-sed as in Chelodina and Pseudemydura, orientedin transverse or oblique (lateral part) and longitu-dinal lines (medial part). For example a specimen(MNHN AC 1887 814), attributed to Emyduramacquarrii, has some longitudinal fine lines, inthe medial part and some lateral pits and shortweak ridges. But the holotype of E. macquarrii(MNHN H 9409) and a specimen of the NaturalHistory Museum (BMNH 86-8-26-5) correctlyattributed to this species, have strong, wide, flatand long ridges separated by grooves, obliquebelow the costals and radiating from a mediopos-terior center below the vertebrals. In most offorms, the carapace is ornamented with granula-tions, pits, sulci and ridges, more or less wide,rounded or sharp, longitudinally and transversal-ly oriented, also depending on the part of thecarapace. The decoration of ridges is strong in theextant specimens of the MNHN collections attri-buted to E. krefftii and E. australis, the ridgesbeing less oblique and medially finer than in theholotype of E. macquarrii, at least in some speci-mens of E. krefftii (MNHN H 1883-380 and381) (the synonymy of E. krefftii with E. mac-

quarrii is admitted by Thomson pers. comm.,but the holotype of the former is not conform tothe holotype of the latter: the study of the indivi-dual and sexual variation of the species, from spe-cimens collected in the area typica of each speciescould verify this assertion). But the ornamenta-tion seems variable within the species, more orless pronounced, and varies with age. Forexample there may or may not be granulationsand pits on the dorsal carapace of E. krefftii, butthere are granulations in young Elseya latisternum(BMNH 71-9-25-8) and pits in adult (MNHNH 7973). The plastron is always more ornament-ed, often more granulate and with well-formedand well-distributed polygons as in Pseudemyduraand Chelodina, although more oriented in lineson the posterior lobe. For example Elseya dentata(NHM specimens) has very well marked, granu-late and small polygons on the plastron andEmydura macquarrii (holotype) has plastral gra-nulate polygons, longitudinally oriented medial-ly, below the pectorals, the abdominals and thefemorals. As seen above, if polygons (the primi-tive design) are shared by all the chelid forms, onlythe Emydura group has longitudinal lines, sulciand ridges, sometimes much developed. Andsome fossil forms with ridges described by De Vis(1897) and considered as Testudines or Chelidaeindeterminant by Gaffney (1981) are evidentlyforms of the group Emydura s.l. (Thomson inprep.). This is important because in the CapeHillsborough Beds, near Proserpine (betweenBowen and Cape Hillsborough), Queensland, anarea considered as Palaeogene and probablyEocene, possibly contemporaneous of RedbankPlains, a partial carapace is preserved (Queens-land Museum, in prep.). It has a typical Emyduradecoration of fine longitudinal ridges on thepleural disc, laterally and medially, and weakpolygons on the peripherals. It is much moredecorated than the Redbank form 4 which isdevoid of longitudinal lines (at least in the pre-served parts), different as a species and probablyfrom a different group of species. It is similar toMiocene South Australian Emydura specimensfigured in Gaffney 1979 and 1991 (such as thespecimen of Emydura sp. from the Ngapakaldi

Lake, Miocene), and described in Burke et al.1983; but fine longitudinal medial and laterallines are also present in adult Elseya novaeguineae(BMNH 13-6-9-20). Longitudinal lines are alsopresent in the holotype of E. macquarrii, as saidabove, but they are coarser. A study of extantmaterial would be necessary to precisely diagnosethe decoration of the Emydura s.l. forms, as near-ly all the specimens in the visited museums arenot prepared. But we can hypothesize that, owingto the decoration, the two Eocene (orPalaeogene) fossil forms were representatives oftwo already separated Emydura s.l. specieslineages. The fossil Oligo-Miocene form fromTasmania described by Warren 1969a, and attri-buted to Emydura sp. aff. E. macquarrii, has aweak decoration of polygons and, besides, somefine longitudinal medial lines under the verte-brals, a decoration differing from that of theholotype of the species. The decoration of itsplastron is not given. This species may be possi-bly closer to the Redbank Plains form than to theProserpine form.

Carapace: shell shapeThe pleural disc was oval, slightly narrowed pos-teriorly but not cordiform, the posterior borderbeing rounded and rather short, not pointed. Itsanterior part is missing, hidden below the plastralpart. The shape of the carapace was elongate, long-er than wide, but not much elongated relative tothe primitive stage, probably as in the fossil formof Emydura from Tasmania (Warren 1969a) andless elongate than the Proserpine form. We can-not say if it was dentate or not nor how much itsperipheral border was expanded, although possi-bly more than the minimum given in the recons-tructed drawing (Fig. 8).

ScutesThe external impression shows the sulci of thecostals 1, 2 (partly), 3 and 4, vertebrals 4 and 5and a part of some marginals sulci. They arestraight and well-marked. The vertebral 4 is justslightly narrower than the vertebral 5, which ismuch wider than the suprapygal. The vertebral 4is also much wider than the costal 4: there is no

narrowing of the vertebrals. The lateral bordersof the vertebral 4 are united in a sharp angle, asin many extant Emydura s.l. (see Goode 1967),particularly in small and young forms, and alsoas in the fossil Emydura from Tasmania. But atthe difference with the latter, the marginals 12do not overlap the suprapygal medially, thevertebral 5 covering all the suprapygal. The cos-tals 3 and 4 overlap the peripherals, as in Elseyanovaeguineae, for example, and less than inEmydura macquarrii and in the Tasmanianform.

Dermal bonesThe bones are firmly linked, without fontanellesbetween pleurals and peripherals, which indicatesan adult form.There are no neurals appearing in dorsal view(Figs 8; 9D), but the centra of the dorsal verte-brae corresponding to neurals 6, 7 and 8 are pre-served and visible in the cast (Figs 7; 9C),between the pleurals 6, 7 and anterior half of 8which do not contact on the mid-line. This alsohappens in some living specimens of Emydura s.l.and in many specimens of living Chelodina (see



FIG. 8. — Emydura s.l. sp. a, form 5, Redbank Plains,Queensland, Eocene (QM F31697), impression of the externalleft lateral and posterior part of the carapace. Abbreviations: C4,costal scute 4; pl1, pl8, pleurals 1, 8; spp, suprapygal; V4, V5,vertebrals 4 and 5. Scale bar: 5 cm.

V4

C4

V5spp

pl8

pl1

above). It is the last remnant of the primitiveseries of the dorsal vertebrae linked to the neuralsand still intercalated between the pleurals ventral-ly. In this case, only the inferior layer of theneural remains, attached to the vertebra. But herewe have only the internal cast of the carapacewith the inferior part of the vertebrae (centrum).We do not see the upper part with the neuralinferior layer which was surely present in thecomplete specimen. In the other living taxa as inthe anterior part of the fossil carapace of RedbankPlains, the neurals have completely disappearedand the dorsal arch of the vertebrae is separatedfrom the carapace, just united at the medial line,the pleurals of each pair meeting in the mid-linedorsally and ventrally. As seen above, rare andoften incomplete neurals have been mentionedin the Emydura sp. from Tasmania (Warren

1969a), in some specimens of extant Elseyalatisternum Gray, 1867 and E. novaeguine-ae (Meyer, 1874) and extant specimens of Elseya sp. aff. E. latisternum from Manning Riverand Elseya sp. from South Alligator River(Rhodin & Mittermeier 1977; Thomson &Georges 1996).The suprapygal is pentagonal, much wider thanlong.The internal cast shows the scars of the ilia belowthe carapace. Each scar is trapezoido-triangularwith rounded angles, pear-shaped, as long aswide, similar to that of the specimen (MNHNAC 1887-814) attributed to Emydura macquarriibut not similar to the specimen (BMNH 86-8-26-5) which is consistent with the holotype inexternal view (internal characters not known inthe holotype): in the second specimen, the scar istriangular trilobate and shorter. The scar of theEmydura s.l. sp. a covers a wide very short part ofthe pleurals 7, a wide part of the pleurals 8 and asmall angular part of the suprapygal (as in Elseyalatisternum fide Thomson pers. comm., but not asin NHM specimens attributed to E. latisternum).It is depressed, well-delimited by a denticulateborder, with shallow rugosities inside. In themiddle part of the scar, there is a rounded zone ofstronger rugosities, on the central part of therib 9, corresponding to a rugose excavated zone in

the iliac surface, as in specimens attributed toE. australis (MNHN) and to E. aff. australis(WA). Emydura macquarrii (BMNH 86-8-26-5and MNHN AC 1887-814 specimens, notknown in holotype) has an apparent rib 9, as inChelodina, thin and sharp. The scar zone is veryweakly rugose in a specimen of Elseya novaegui-neae (MNHN P 1880-467), variably rugose inRheodytes leucops and Emydura krefftii. It is notprepared in the Natural History Museum speci-mens of E. dentata and E. novaeguineae. As wehave seen above in the section on Chelodina alan-rixi n. sp., the shape of the iliac scar is quitevariable in chelids and it derived independently inall the lineages, with some homoplasies. It is tri-angular with rounded angles to oval in Chelodina,rounded-oval in Pseudemydura and most oftentriangular, inverted or not, in Emydura s.l., some-times also with rounded angles. The longer trian-gular shape is primitive in Eupleurodira and themore rounded or oval shape is derived. In most ofobserved specimens of the Emydura group(Emydura and Elseya), the scar is limited to thepleural 8 and suprapygal and it does not contactthe pleural 7 any more. White (1997) noted that“the pelvic scars on pleurals 8 and the suprapygalsare more typical of Elseya”. We observed a scarreduced to pleurals 8 and suprapygal in Emyduramacquarrii (BMNH 86-8-26-5, specimen exter-nally consistent with the holotype of the species),Rheodytes leucops (Queensland Museum andAustralian Museum specimens) and Emydurakrefftii (Queensland Museum specimens andMNHN H 1983-380 and 381). The scar is stillon the pleurals 7 in a specimen of the QueenslandMuseum attributed to Elseya dentata (while not inmost other specimens attributed to this species,including QM J47911, attributed now to E. lava-rockorum [Thomson pers. comm.]) as in the spe-cimen attributed to Emydura macquarrii(MNHN AC 1887-814) and observed specimensattributed to E. australis (MNHN) and E. aff.australis (WA). Actually, the iliac scar, in theRedbank Plains form 5, which clearly covers thesuprapygal and hardly the pleural 7, is similar tomany chelids and conforms to Emydura s.l. in therugosities and shape.





FIG. 9. — Redbank Plains, Queensland, Eocene; A-B, Emydura s.l. sp. a or b?, form 6 (QM F37913), internal mold of an anterior partof the shell; A, dorsal part; B, ventral part; C-D, Emydura s.l. sp. a, form 5 (QM F31697); C, internal mold of the left lateral and poste-rior part of the shell, anteriorly covered by the external impression of the left lateroposterior part of the plastron; D, impression of theexternal left lateral and posterior part of the shell. Abbreviations: ax.pr, axillary process; ip, inguinal process; n1, remnant of neural 1;nu, nuchal; pl5, pleural 5; r1, r2, thoracic ribs 1 and 2; ento, posterior part of the entoplastron; hyo, hyoplastron; hypo, hypoplas-tron. Scale bars: 2 cm.

A

r1

nun1

ax.pr

r2

ippl5

ento

hyo

hypo

A, B

B

C

D

C, D

PlastronThe part of left plastron superposed to the cast ofthe internal carapace (Figs 7; 9C) consists of theposterior medial part of the hyoplastron and ofthe medial part of the hypoplastron (the axillaryand inguinal processes are incomplete laterally)and the xiphiplastron, less its posterior extremityat the anal notch.The posterior lobe is narrow without wideningforward of the anals at the femoro-anal sulcusand without narrowed pointed xiphiplastralpoints. The lateral border of the femoral scute isslightly incomplete, but the posterior lobe borderwas nearly straight, only slightly convergingtowards the anal notch (Fig. 7), less than in thespecies studied above, form 4, Chelodina sp. c?The anal notch, from the marks on the brokennodule, had to be relatively wide and short as inthe above form 4.The posterior lobe is elongate, relatively longfor its width (and may be still longer thanreconstructed in the Fig. 7), with an estimatedratio width/length of 94-100%. The elongatedposterior lobe is a derived character of theEmydura group among the Australian chelids,immediately observable in figures (see Goode1967), and different from Chelodina andPseudemydura with short posterior lobes. Theposterior lobe ratio, width at abdomino-femoralsulcus to full length, measured in some speci-mens, is: 84.69% in Rheodytes leucops; c. 95% inElseya latisternum, 97% in E. novaeguineae and102% in E. dentata; 97%, 97.17% (holotype)and 103% in E. macquarrii and c. 98% in a spe-cimen attributed to E. australis. The ratio is141% in Pseudemydura. In Chelodina, the ratiosvary from 103% (103.44%, 103.17% and111.76%) in C. oblonga to 138% in C. novae-guineae. The plastron had no reduced bridgelength. The abdomino-femoral sulcus finishesin the bottom of the inguinal notch instead offurther backwards on the lobe border, as itoccurs in Chelodina (see above, Chelodinasp. c?, Fig. 6). The posterior lobe is not muchrounded and widened relative to the base as itoccurs in Pseudemydura (see Burbidge et al.1974).

DISCUSSION

The Redbank Plains form 5 is clearly a memberof the Emydura group. Owing to the very weakdecoration (although eventually not completelypreserved in the dorsal part of the shell) we candifferentiate it from the species from Proserpine(Cape Hillsborough Beds) which has a strongerdecoration of longitudinal lines, although fineand not the strongest possible in the group (seethe figures in De Vis 1897; Gaffney 1979, 1981;Goode 1967; Burke et al. 1983). The RedbankPlains form is surely different from the extantspecies E. macquarrii s.s., in being more rounded(shortest behind), less decorated and without amark of rib 9 in the iliac scar. Because of its roun-ded shape, its “faded” decoration and its verte-brals wide and with angulate lateral angles, it issimilar to the specimen from Tasmania (Warren1969a) (a latisternum group member fideThomson pers. comm.) It specifically differsfrom the latter by the marginals 12 not overlap-ping the suprapygal. But, although possible, it isnot sure that they both belong to the E. macquar-rii group, to which the Tasmanian form is refer-red. The Redbank Plains Emydura s.l. sp. a is alsosurely different from the Redbank Plains form 4,described above, doubtfully attributed toChelodina sp. c?, although possibly belonging tothe Emydura sp. group, in the strong differencein the plastral ornamentation of the latter, withsmaller granulate polygons like those of Elseyadentata, for example, instead of wider medialpolygons like those of Emydura macquarrii, forexample.

Emydura s.l. sp. a or b?

DESCRIPTION

Material (Fig. 9A, B)The specimen of the Redbank Plains form 6 isrepresented by QM F37913. It consists of arounded nodule with the ventral view of a partialshell, with the natural mould and some bonefragments of pleurals 4-8 and the suprapygal and,on the other side, the impression of the medialpart of the plastron, without the most anterior





FIG. 10. — A, Chelodina alanrixi n. sp., form 1, Redbank Plains, Queensland, Eocene (QM F18344), 40-41 cm long, reconstruction ofthe carapace, dorsal view, missing parts doted, presenting generic identities and specific differences with C. expansa in B-D; a, flat-tened, large and wide carapace as in C. expansa; b, narrow vertebrals, the first one narrower than the nuchal bone, the second tofourth narrower than the first and fifth, the third particularly narrow, vertebrals narrower than in C. expansa except the fifth that iswider than the suprapygal bone; c, polygons of the decoration c. 1/3 smaller than in C. expansa (see D and compare with Fig. 1B); d,8 neurals present, against no one in C. expansa; e, vertebral 5 wider than the suprapygal contrarily to C. expansa; f, long and flat pos-terior extremity, as in C. expansa, slightly pointed as in males in C. expansa; B, C. expansa, extant (MNHN AC 1914-178), 37.5 cmlong; a, large and wide carapace as in C. alanrixi n. sp. (anteriorly narrower in males); b, wide vertebral 1 wider than the nuchal bone,the vertebrals 2 to 4 (the fourth subdivided) progressively narrowing; c, large polygons (see D); d, no neurals (never); e, vertebral 5narrower than the suprapygal; f, long and flat posterior extremity, slightly pointed as in C. alanrixi n. sp. but more rounded border (afemale); C, C. expansa Gray, 1856 (pl. XII), holotype, from Goode (1967) and Wermuth & Mertens (1961), 35 cm long, a male (anteriorlynarrower and posteriorly pointed, plastron with a concavity); D, C. expansa, extant (MNHN AC 1914-178), 37.5 cm long, detail of thedecoration of the carapace in the area of the vertebral 4 (subdivided here), compare with Fig. 1B. Scale bars: A, B, 10 cm; D, 2 cm.

A

D

B

a

a

b

c

d

e

b

c

d

e

f

f

C

part (epiplastra, entoplastron) and the most pos-terior part (xiphiplastra).

Measurements (in cm)Maximum preserved length and width of thefragment: 10.8 and 15.Estimated length and width of the carapace: c. 21and 17.5.Plastral bridge length: c. 4.2.Anterior lobe width at its base: 7.6.Maximum estimated entoplastral length: 2.Medial hyoplastral length: 5.2.

DecorationIt is not preserved.

Shell shapeThe plates were relatively thick for their lengthand there is no indication of fontanelles. It wasfully adult. Based on the preserved parts, i.e. thescars of the thoracic ribs 1 and 2, the axillary pro-cess, the entoplastral size, the distance betweenthe entoplastron and the hyo-hypoplastral sutureand the bridge proportions, the species belongs tothe Emydura group. It is therefore possible toreconstruct a carapace of Emydura s.l. shape. Thisis not much variable in the group, i.e. there isalways a carapace particularly elongated relativeto the primitive length and expanded posteriorlyand slightly narrowed anteriorly, with a narrowplastron a little smaller than the carapace, with aopen U-shaped anterior lobe, a relatively longbridge and a long posterior lobe. In the Emydura group, the posterior border ofthe carapace is more expanded in some speciesthan in others, some are more rounded and someare more elongated. The anterior lobe may bemore narrowed and the posterior lobe may bemore or less narrowed posteriorly at the femoro-anal sulcus, depending on the species to which itbelonged.

Dermal bones of the shellThe nuchal is moderately wide (the anterior partis missing) and the pleurals 1 are moderatelylong. There are no neurals between the preservedpleurals 1 to 5 which are wide for their length.

Between the two pleurals 1, the neural arch ofthe dorsal vertebra 1 is preserved in its medialpart (reduced anteriorly and posteriorly) whichmeans that dorsal vertebra 1 was still intercalatedbetween the plates while between pleurals 2 to 5there are no more intercalated vertebrae andno more neurals at all. The axillary processenters pleural 1 at the mid posterior part of per-ipheral 2 and at the beginning of peripheral 3,anterior to rib 2. It covers c. 2/3 of the width ofpleural 1, being well-rounded and well-overlap-ping thoracic rib 2 at that place. The lateral partof the impression of the right pleural 5 bearsthe short rounded extremity of the inguinalprocess.

PlastronThe impression of a good part of the entoplas-tron is preserved and easy to reconstruct in itslength. It was small and largely separated fromthe hypoplastra (slightly more than two times itslength) as in Emydura s.l. This is the differencefrom Chelodina where the entoplastron is large inthe anterior lobe and closer to the hypoplastra(distance of a little more than its length inC. expansa and C. oblonga, less than its length inC. longicollis or in C. steindachneri). The situationin Pseudemydura is intermediate; the entoplastronis small, but the anterior lobe is wide and shortand the entoplastron is separated from the hypo-plastra by a distance of a little more than its length.As in Emydura s.l., the bridge is long relative tothe width of the plastral lobes at their base, itslength being clearly more than the half the plas-tral width, different from Chelodina andPseudemydura where it is as long or shorter.

DISCUSSION

As seen above, the specimen belongs clearly tothe Emydura group in light of these features: thecharacters of the pleurals 1, the entoplastral size,the distance between the entoplastron and thehyo-hypoplastral suture and the bridge lengthrelative to the width of the lobes. In the Emyduragroup, the axillary processes generally enter thepleural 1 from forward, at peripherals 1 to 3depending on the taxa (it is more derived where



it is more forwardly positioned). Within theChelidae, Emydura s.l. is particularly derived inits long bridge and more forwardly prolongatedaxillary processes. The axillary process enterspleural 1 and goes obliquely backwards to jointhoracic rib 2 that it covers, up to half the widthof pleural l. It is forward positioned relative tothe primitive condition which is still found inChelodina and Pseudemydura, where the processenters at peripheral 3 and directly covers thoracicrib 2. In the Emydura group, the more primitivecondition is that of Elseya latisternum, Rheodytesleucops and Elusor macrurus (see Thomson et al.1997; QM and BMNH specimens) where theprocess enters at peripheral 3 just forward butclose to thoracic rib 2, that it covers up to themid-width of the plate, i.e. more widely than inthe primitive condition seen in most ofChelodina species and in Pseudemydura. InChelodina and Pseudemydura, the process, enter-ing at peripheral 3, either is still short laterallybut, directed obliquely backwards, may cover asmall part of pleural 2 (for example C. steindach-neri, C. longicollis, Pseudemydura), or it is alsoprolongated up to pleural 2 and furthermore it iswide up to the mid-width of pleural 1 (C. expansa,with the more derived condition in Chelodina). In the Redbank Plains form, the position of theaxillary process which enters pleural 1 at theposterior part of peripheral 2 and beginning ofperipheral 3, anterior to rib 2, is consistent withthat of various species of the Emydura groupmoderately derived on that point: that of Elseyadentata (BMNH 765-19-77, Thomson et al.1997), Emydura macquarrii (BMNH 86-9-26-5, MNHN 1897-814), specimens attributed toE. kreftii (White & Archer, 1994), E. novaegui-neae (BMNH 1835-5-10-177), extant Elseyalavarackorum in Thomson et al. 1997, Emydurasp., fossil from Lake Tarkarooloo, Miocene,Burke et al. 1983. In these forms, the process ismore or less thin where it contacts withpleural 1 and either situated in front of the pos-terior part of peripheral 2 or just backwards, atthe limit of both peripherals 2 and 3. It is clear-ly situated more backwards than in the fossilElseya lavarackorum White & Archer, 1994,

Pleistocene from Riversleigh, f igured inThomson et al . 1997, Emydura subglobosa(Thomson et al. 1997) and young (MNHN P1880-467), where it is positioned at mid-lengthof peripheral 2. It is still more backwards situatedthan in “E. australis” (AM, R26581), where it enterspleural 1 at peripheral 1, which is the more derivedcondition in the Emydura group. But it is moreforward positioned than in Rheodytes leukops(see Thomson et al. 1997) and Elseya latisternum(White & Archer 1994; BMNH 71-9-25-8)where the process enters at peripheral 3. The specimen, adult, is approximately the samesize as the other Emydura s.l. specimen fromRedbank Plains described above and the doubtfulspecimen of Chelodina sp. c? (possibly a specimenof Emydura?), also adults: c. 20 cm in sp. a, c.23 cm in “Chelodina sp. c?”, and c. 21 cm inform 6. The presence of the remains of the neuralarch 1 between the pleurals 1 can be compared tothe presence of the remains of neurals 6 to 8 bet-ween the pleurals 6 to 8 in Emydura s.l. sp. a,thus showing that both forms could belong to thesame species without a complete neural reduc-tion. The possible shape of the plastron of form 6conforms to the plastron of form 5. It is possiblethat the carapace was slightly wider than inform 5. This species cannot be of the same groupas the species from Proserpine nor the same as thespecies of the form 4, if it is a Emydura s.l. insteadof a Chelodina.Even if only one species of Emydura s.l. existed inRedbank Plains, two species of two distinctgroups existed in the Palaeogene of Queensland.In fact many more extant species exist than wereknown in the last Century (Cann 1978; Wells &Wellington 1985; Iverson 1992) and a rediagno-sis of each species ought to be given, based on theanatomy of the skeleton, allowing better defini-tion of the new subgroups of Emydura s.l.

Chelidae indet.

DESCRIPTION

This is a fragment of a rather large shell,QM F12361, in ventral view with three median



pleurals and adjacent fragments, with the lateralpart of corresponding neurals and fragmentarycorresponding plastral part in ventral view. Thereare important lateral fontanelles between peri-pherals and buttresses. It cannot belong toChelodina owing to the absence of decoration.The preserved fragment is c. 14 cm long.

CONCLUSION

The Redbank Plains turtle fauna is, in the presentstate of knowledge, limited to Family Chelidae;no cryptodiran turtles are yet recognized.The Redbank Plains fauna is well-differentiatedwith representatives of two of the three groups ofliving Australian chelids: Chelodina and Emyduras.l. There are three species of Chelodina, belong-ing to two or three groups of extant species.There are one or two species of Emydura s.l. andone indeterminate chelid. The oldest known spe-cies of Emydura s.l. are represented here, olderthan the Oligocene form from Tasmania(Warren 1969a) and that the Oligo-Mioceneforms from Riversleigh (Gaffney et al. 1989;White 1997). With the Emydura s.l. form fromProserpine, also from the Palaeogene and maybecontemporaneous, there were during Palaeogenetimes in Queensland two species of the Emyduragroup, belonging to two already differentiateddifferent lineages. As far as Chelodina is con-cerned, the Redbank Plains forms may be also theoldest members of the genus if we exclude thematerial attributed to Chelodina insculpta by DeVis (1897) which possibly includes Eocene mate-rial of Eight Mile Plains (but not the figuredmaterial, see Thomson in prep.). Pseudemydura isnot represented at Redbank Plains and the oldestattested representative of the genus is that ofRiversleigh Station, Oligo-Miocene of northernQueensland (Gaffney et al. 1989). In Emyduras.l. as in Chelodina, the decoration is an impor-tant character. The age of the fauna is shown bythe small size of the polygons, smaller inChelodina from Redbank Plains than in theextant species, as well as in the dubious Chelodinasp. c? (or Emydura sp?). In Chelodina, it is also

seen in the wide vertebral 5 relative to the pygalwhen, in the later species, the vertebral 5 is red-uced in the forms with narrowed vertebrals 1 to4. But, surprisingly, C. alanrixi n. sp., the formof Chelodina with narrowed vertebrals 1 to 4, hasthe most derived condition for the character,which indicates a possibility of homoplasy for thenarrowing of the vertebrals 1 to 4 as well as of thevertebral 5. Also primitive is the character of theperipherals, not much expanded posteriorly. InEmydura s.l., the carapace of the form a was notmuch elongated and narrowed but it was well-derived by the reduced decoration.This material reveals the differentiation of theforms as already well-established in EarlyPalaeogene time and a suite of lineages allowingfor the erection of several genera for each groupof species, Chelodina as Emydura s.l. thus repre-senting higher taxonomical categories. Severalauthors have recently argued for the subdivisionof the Emydura group. Legler & Cann (1980)erected Rheodytes leucops and Cann & Legler(1994) erected Elusor macrurus. Thomson et al.(1997) estimate that the Emydura group includes,besides Rheodytes and Elusor, three subdivisions ofthe group: Emydura s.s. and two subdivisions ofElseya, one for the dentata-novaeguineae groupand one for the latisternum group. As observedabove, the attribution of the Redbank Plainsmaterial to one of these subdivisions is impossibleuntil the diagnostic apomorphic osteological cha-racters, applicable to our fossils, are defined andgiven with a well-established cladogram in a com-parative work, based on the type specimens of thespecies. Wells & Wellington (1985) revived thesubdivisions of Gray and erected new genera, aswell for Chelodina as for Emydura groups. Thereis no solid argument in their work. The diagnosisof the future subdivisions would have to includenot only autapomorphic characters but also theirintegration in the evolutionary stage of the gene-ra, all of which is completely missing in the data,and integrate the South American forms with theSouth Australian forms. We are not only waitingfor the study of the osteology and the externalcharacters of the extant species, but also for theresearch into the primitive and derived states of



each character. This requires taking outgroupsoutside Australia: in primitive Pleurodira and inPelomedusoides, following the evolution of eachgenus. In this way the homoplasies will be madeclear.The Redbank Plains material is insufficiently pre-served to resolve the problems and this study isjust a first step. For the moment, we do notknow: 1) if Chelodina alanrixi n. sp. is or not partof the Chelodina group with narrowed vertebrals,because of the contradiction between the widevertebral 5 and the much narrowed vertebrals 1to 4, and if Chelodina form b is or is not part of amonophyletic group with C. steindachneri; 2) thegroup to which Emydura s.l. sp. a belongs and ifthe specimen from Proserpine is a member of theE. macquarrii group.It is certain that at this Palaeogene time severalspecies were differentiated. It is also certain thatthe three Australian genera were differentiatedbefore the Palaeocene, as suggested by the disco-very in the Palaeocene of western Australia. It isevident if we follow the cladistic study of thefamily by Gaffney (1977), although within thisstudy the problems of vicariance betweenAustralia and South America could be examinedand clades could be established instead of grades,when homoplasies are taken into account.Overall, the age of the group in Argentina hasbeen confirmed by the discovery of the very diffe-rentiated chelid forms in the Cretaceous (Aptianto Maastrichtian) of Patagonia (Broin 1987,1988; Broin & Fuente 1993; Lapparent de Broinet al. 1997; Lapparent de Broin & Fuente 1999;Fuente et al. 2001), with the extant genera,Phrynops, Chelus and Hydromedusa, already definedbeside Emydura-like forms and more primitiveforms. The absence of Chelidae in EarlyCretaceous times in Australia may be, therefore, aproblem of continental barrier between West andEast of Gondwana: actually, in the southernGondwana fauna of the Early Cretaceous, theSouth American chelids appear as an Occidentalgroup and the fauna of Victoria, South Walesand Queensland as an Oriental group. It may bea problem of availability of geologically adequatelocalities in convenient latitudes. As they are

fresh-water turtles, the Chelidae may be found incontinental beds, or exceptionally in marinelayers near the shore. As poikilothermic animals,Chelidae require a minimal yearly temperatureratio, with a short period of high temperatures orwith a longest period of more moderate tempera-tures, higher than for birds and mammals. And aspleurodiran turtles, although they are more tole-rant than Pelomedusoides, they never becameaccustomed to the cold weather that can affectthe Cryptodira, although they can hibernate inthe mud (as well as estivate). In the most sou-thern part of Australia, their most southern habi-tat, they presently live in an area from around 10°minimum in July (the same minimum as in theirsouthern habitat in Argentina, in the North ofBuenos Aires Province) or, exceptionally, evenless than 10 °C (Thomson pers. comm., forC. longicollis) up to 18° C minimum in January.But the question is whether the low temperatureperiod of the year has to be short relative to thehigher temperature period, to allow the eggs tomature. On the other hand, it is possible that someextant Australian Quelidae such as C. longicollismust to be more adapted to cooling than the pri-mitive Mesozoic forms and other extant forms(they have had much time to adapt), as someTrionychidae did. The problem of a sufficientlyhigh yearly temperature ratio, besides the pro-blems of structural barriers and of the possibilitiesof a stable fluviatile network, is probably animportant part of the reason they do not appearin the southern Cretaceous localities of Australia(see Dettmann et al. 1992: fig. 24).

AcknowledgementsWe first warmly thank Dr Alan Rix for the disco-very of the specimens, their gift to theQueensland Museum, and for his help in the pre-sent study, particularly concerning the geologicalreferences about the fossil localities and referenceson fossil and living Australian chelids. For theirhelp for the comparative material, we aregrateful to Dr J. Covacevich and P. Couper,Vertebrates, Zoology, Queensland Museum,Brisbane; Dr A. Greer, Department of Zoology,



Dr A. Ritchie and R. Jones, Department ofPalaeontology, Australian Museum, Sydney; DrM. Hutchinson, Department of Zoology and DrN. Pledge, Department of Palaeontology, SouthAustralian Museum, Adelaide; Dr G. Kuchling,University of Western Australia, Department ofZoology, Nedlands; Dr J. Long, Department ofPalaeontology and Dr L. Smith, Department ofZoology, Western Australian Museum, Perth; DrT. Rich, National Museum of Victoria, NaturalHistory Division, Melbourne; Dr P. Vickers-Rich and Mrs L. Kool, Monash UniversityDepartment of Earth Sciences, Clayton, Melbourne;Dr A. Warren, Zoology Department, La TrobeUniversity, Bundoora; Arthur White, Universityof New South Wales. In Argentine, we warmlythank for his welcome Prof. J. Bonaparte, Museode Ciencias Naturales de Buenos Aires andDr M. S. de la Fuente, Museo de CienciasNaturales de La Plata. At the Natural History Museum,London, we kindly thank Dr C. McCarthy,Department of Zoology, Reptiles, and SandraChapman, Department of Palaeontology. At theMuséum national d’Histoire naturelle de Paris, weare particularly grateful to R. Bour, Laboratoire deZoologie des Reptiles et Amphibiens, for his helpand commentaries, to F. Pilard and H. Lavina(figures) and L. Merlette (photographs), Labora-toire de Paléontologie, and to F. Renoult, Labo-ratoire d’Anatomie comparée (osteological material).We also thank the authors of the reviews sent toGeodiversitas and including S. Thomson. At themoment this paper is sent to press, variousimportant papers on chelids of S. Thomson(pers. comm., in prep. or in press but referencesnot communicated) and others (includingMegirian & Murray 1999), are not received hereand, therefore, not available for the present study.

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Submitted on 11 October 1999;accepted on 14 September 2000.



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Eocene chelid turtles from Redbank Plains, Southeast …sciencepress.mnhn.fr/sites/default/files/articles/pdf/g... · 2015. 5. 6. · turtles are chelids, belonging to at least five