Re-evaluation of Emydttra lavarackorum: identification of a living fossil

9 Pages·1997·4.5 MB·

by  Scott Thomson

RE-EVALUATION OFEMYDURA LAVARACKORUM: IDENTIFICATION OF
ALIVING FOSSIL
SCOTTTHOMSON. ARTHUR WHITEANDARTHURGEORGES
Thomson, S.A., While, A. & Georges, A. 1997 06 30: Re-evaluation of Emydttra lav-
arackorum: Identification ofa living fossil. Memoirs ofthe Queensland Museum 42(1):
327-336. Brisbane. ISSN0079-8835.
Po.st-crani.-3i osteological characterscan be usedtodiagnoseAustralian short-necked chelid
turtles to genus. Morphological examination of the Pleistocene fossil Emydura fav-
arackonmu from Riversleigh, shows that it is aligned with the genus Elseya not Emydura
and shouldbereferredtoasEiseyalavarackorum(White&Archer, 1994).Furthermore,the
fossil specimen isnot distinguishable from an undescribed extant form ofElseya from the
Nicholson drainage, with which it sharesone unique featuresothisnameshouldapplyalso
to thb extant form, identified todate only from electrophoreticdata. It is Australia's first
living fossil turtle, an extant population of a Pleistocene taxon. Chelonia, Chelidae,
PleistoceneJbssil, turtle.
Scott Thomson <£ Arthur Georges, Applied Ecology Research Groupawt CRCforEresh-
to&terEcology, UniversityofCanberra, P.O. Box1, BetconnettACT£616.Australia;Arthur
White, School$fBiologicalSciences, UniversityofNewSouth Watex,P.O.BoxI,Kensington
NSW U
2033, Australia; April 1997,
The taxonomy of Australian chelid turtles is with somepelvic material present. The lengthof
poorly known and in direneed ofreview (Cogger the plastron is 390mm (White & Archer, 1994)
et a!.. 1983). Recent electrophoretic surveys which corresponds to a carapace length of ap-
(Georges & Adams, 1992; 1996) have revealed proximately 420mm. Two other plastra fromthe
thatin someinstances,currentlyacceptedspecies same site were alsocollected but not described*
boundaries are difficult to justify and in others, White and Archer (1994) assigned the speci-
what are currently regarded as single species are men to Emydura on the mode ofthe insertion of
ut fact two or more. The detailed morphological the anterior bridge into the ventral surface ofthe
adn0a1lbyeseenscroenqduuicrtededt(obuvtersiefeyTthhoemsesofnin&diGnegsorhgaevs.e acnatrearpiaocre.brTihdegyefiosuanndgtlheadtisntetehpeldyerbiavcekdwsatratders.utoV-
1996), and until recently it was not possible to wards the rib/gomophosisis (called transverse
distinguish even between extant short-necked process in White & Archer, 1994), whereas in all
genera on the basis of osteological characters other cheilitis the anterior bridge was found to
JGaffney. 1977).Thispaucityofosteologicaldata formacontinuouslinewiththerib/gomophosisis.
suitable for distinguishing the extant genera In this paper, we reassess the generic assign-
makes the identification offossil forms, most of
wmhaincyhinasrteanciensc,ocmhpelleitdefosspsielcsihmeanvse,bedeinffiacsuslit,gneIdn mwietnhtpoofstth-ecrfaonsisiallbcyhacroamcptaerrisntagtetshewfeosshialvmeatfoetuinadl
useful in separating extant genera ofAustralian
tocither Chelodina orEmydura. with little or no short-neckedchelidturtles. We alsopropose that
fvidence presented to eliminate the possibility
that the short-necked forms among them may be the fossil taxon isextant, adistinctive, undescribed
formclosely aligned withElseyadentata.
Elseya, Rheodytes orElusor
In 1994 a partial carapace and associated plas- MATERIALS AND METHODS
iron from Riversleigh was described as a new
species, Emydura lavarackorum, by White &:
Axcbex (1994.1. The fossil specimen was from Specimens ofeachofthe short-necked spL
Terrace Site, a fluviatiie site on the Gregory identified using electrophoresis by George?, and
aulhors interpretedthesedimentsas Adams(1996)wereobtained frommuseums, the
,
being Pleistocene in age because ofthe presence ConservationCommissionoftheNorthern Terri
of remains of Dtprotodon optatwn (White & toryandthe UniversityofCanberra. Whereforms
Archer, 1994). The holotypeconsistsoftheante- have noi been included in published keys or de
riorhalfof the carapace with some anterior pe- Si Minions, the specimens were selected from
ripherals and an essentially complete plastron those lodged as vouchersu>accompany the
328 MEMOIRS OFTHEQUEENSLAND MUSEUM
FIG. 1. Ventral view ofthe anteriorcarapaceofshort-necked turtles showing the bridge-carapace suture (BCS) the
rib/gomophosisis(R)onpleural 1 (PI)andtheirrelationshiptothevertebralcolumn(V)andtheperipherals(Pe).A-B,
Pseudemydum(UCO178).C-DElseyasp.aff.E.latisternwn(Manning)(QM59289);E-F,Elnsormacrums{VCQ\84).
IDENTIFICATION OF ALIVINGFOSSIL 32«J
IXOphotetk dala. The specimen collection wils laterthree arccurrently umicscribed. It is notthe
.supplemented by limited field sampling. purpose of this paper 10 describe new genci.
Each specimen was skeletonised by removing lor consistency, we use the nomenclature of
excess soft tissue and feeding the reuwitting car- Ge<>rges <& Adams 1.1992) and Legler(1981)and
case to dermcstid beetles. The skeletal material recognise six groups of Australian short-necked
> bleached in 5% sodium hypochlorate solu- chelid at generic level: Elnsor, Emyxiura,
tion, and Ihe process slopped by immersion in Psetidemyd.vra, the Etxeyti
100% ethanol. Plastra were separated irom cara- tatisternum genericgroupandtheElseyadentata
paces by disarticulating Ihe plasiral-earapacial generic grOlftp,
suture between the hyo- and hypoplasia of die Throughout this paper, names ofthe bony ele-
pij.stron and the lateral peripherals of the cara- mentsoftheshell andthe overlyingscutesfollow
pace. This was done by the carefully heating the those ofZangcri (3969). A complete list ol the
carapaceuntil the sutures become mobile andthe .specimens examined in this Stud) will be fmaul
tfotl was then gently prised off. This also in AppendixA.
required disarticulation of the pelvis from the
carapace. Characters potentially diagnosticat the RESULTS
generic level were examined to establish their
consistency across a range of specimens within Five characters were identifiedasdiagnosticaL
ihe polytypic genera Elseya and Emxdura, and I ic level Where polarity is indicated, it was
across a range o! specimens within each species. determined In comparison with South American
chchds and African peloniedusids in a cladistie
The fossil specimens of Ernvdura luv- analysis (Thomson & Georges, unpublished
arackorum wereexamined todeterminethe pres-
ence of character states which are gencrieally data). Only thosecharactersrelevant to the iden-
tification ofthe fossil specimen are presented.
diagnostic inextantlaxa The fossil specimenwas
then assigned to genus. ANTERIOR BRIDGE STRUTS Character A
Throughout this paper, we refer to a generic Contact with Pleural
I
gtfOUp as a group of species that are sufficient!) AU In theprimitive stale, the posterior edge of
distnut collectively to warrant recognition at the diebridge-carapacesuturerunsparallel andadja-
level oJ genus, though this has not yet been tor centtothe rib/gomophosisisofpleural 1 (Pig. IA-F).
mally established. These groups were first iden- Al. In the derived state, the posterior edge Ol
tified by Leglcr (1981), have a foundation in this suture contacts the rib/gomophosisis at its
elcctrophorclic studies (Georges & Adams. anterior end, but is set at a forward divergent
1996), and have been referred to since several angle ofbetween 15 and 50°. This angle is most
times in the literature. Incontrast, a speciescom- pronouncedin Emvdura, least inRheodytes i
plex is agroupofspecies, all butoneofwhich are 2A-K 3A-D).
.indescribed, which togethct presumably repre- Character B. Bridge suture shape.
sent adistinct ciade but which are not considered Bl. The anterior and posterior edges of the
distinctive enough to warrant recognition at the b<idgc-carapace suture diverge from their point
level of genus. cl congruence closest to the vertebral column
We icfet to the Elseyadentata speciescomplex The widest extent of Ihe suture is distal 10 the
as comprising the distinctive forms of Elseya vertebra)column and there is HO medial constric-
from coastal Queensland currently assigned to tion (Fig. IA-F)
! hfyaitemata, and the Northern Territory tomis B2. The anterior and posterior edges of the
including Elseya dentata (sensil strtcio) and bridge-carapace suture are parallel or clott
Elseya sp. aff, E, rfnuaUi from the Alligator Rtv- with a prominent suture surface between them.
Effi region (Georges & Adams, 1996).TheElseya There is no medial constriction (Pigs 2A-B, E-F
ileniatageneric group (sensu Legler, 1981) com- 3A-BI.
prises the Elseya dentata Species complex plus B3.The bridge-carapacesutureisexpanded for
Elseya novaeguineae and Elseya branderhorsti its full length, hut more so at extremes, there
from New Guinea. The Elsexa latlstemum ge- beingan obvious medial constriction (Fig. 2Bi
neric group comprises Elseya lati&ternwn (sensu B4. The bridge-carapace suture narrows i;
strieto), arelated formfromtheheadwatersofthe its widestpoint proximal tothe vertebral col
Darling Riverdrainage and a sibling species pait and ccnsiiills completely to forma ridgeconflu-
coastal NeV South Wales (Georges & ent with the edge formed by ihe ventral stun
Adams. 19%;Thomson & Georges 996). The the peripheral bones (Fig. 3C-Di.
330 MEMOIRS OFTHEQUEENSLANDMUSEUM
FIG. 2. Ventral view ofthe anteriorcarapaceofshort-necked turtles showing thebridge<arapace suture (BCS) the
rib/gomophosisis(R)onpleural 1 (PI)andtheirrelationshiptothevertebralcolumn(V)andtheperipherals(Pe). A-B.
Rheodytesieukops(UC0173).C-D,Elseyadentata(QM59277).E-F,Elseyalavarackorwn(extant)(QM46284).
.
IDENTIFICATION OFALIVINGFOSSIL 331
FIG. 3. Ventral viewofthe anteriorcarapaceofshort-neckedturtles showing the bridge-carapacesuture(BCS)
therib/gomophosisis(R)onpleural 1 (PI)andtheirrelationshiptothevertebralcolumn (V)andtheperipherals
(Pe). A-B,Elseya lavarackorum (fossil) (QM24121). CD,Emydurasubglobosa (UC0172).
RIB/GOMOPHOSISIS OF PLEURAL 1. Char- DORSAL CHARACTERS. Character D. Rela-
acterC. Rotation ofthe Rib/Gomophosisis. tive width ofVertebral 1
CO. The ventral surface of the distal extent of Dl. 1st 3 vertebral scutes equal or subequal in
the rib/gomophosisis is rotated obliquely, to face width (Figs 4A-D,5B).
ventrally butwithposteriorinflection(Figs 1A-F, D2. 1st vertebral scute wider than 2nd and3rd
2A-B). (Figs4E-F, 5A).
CI. The rib/gomophosisis shows no such tor- CharacterE: Cervical Scute.
sion distally (Figs 2C-F, 3A-D). EO. Cervical scute typically present (Fig. 5B).
332 MEMOIRS OFTHEQUEENSLANDMUSEUM
FIG.4.Dorsalviewoftheanteriorcarapaceofshort-neckedturtlesshowingtherelativesizebetweenthevertebral
scutes (V) and the presence orabsence ofthe cervical scute (N) theirrelationshiptothecostal scutes (C) and
marginals (M). Note the indentation at the anteriorofsome taxa. A, Pseudemydura (UC0178). B, Elseya sp.
aff.E. latisternum(Manning)(QM59289).C,Elusormacrurus(UC0344).D,Rheodytesleukops(UC0173).E,
Elseyadentata (QM59277). F,Elseya lavarackorum (extant)(QM46284).
IDENTIFICATION OFALIVINGFOSSIL 333
FIG. 5. A-B, Dorsal view ofthe anteriorcarapace ofshort-necked turtles showingthe relative sizebetweenthe
vertebral scutes (V)andthe presenceorabsenceofthecervical scute (N) theirrelationship tothecostal scutes
(C) and marginals (M). Note the indentation at the anterior of some taxa. A, Elseya lavarackorum (fossil)
(QM24121).B,Emydurasubglobosa(UC0172).C-E,Ventral viewoftheplastrons showingthearrangementof
thesulcibetweenthehumeral (H)andpectoral(P)scutes,alsoshownarethegularscutes(G)andtheintergular
(I). C, Elseya lavarackorum (extant) (QM46284); D, Elseva lavarackorum (fossil) (QM24121). E, Elseva
dentata{QU59211).
El. Cervical scute typically absent (Figs 4E-F, bridgesutureand therib/gomophosisisofpleural
5A). one; parallel anterior and posterior edges of the
Thedistribution ofthecharacterstates foreach
bridge-carapace suture throughout their length,
tEamxyodnurias lparvoavriadcekdoriunmThaabdlea c1o. mTbhienathioolnotoyfpea widely spaced, with no medial constriction; no
widelydivergentangle(45°)betweentheanterior distal rotationofthegomophosisisofpleuralone;
334 MEMOIRS OFTHEQUEENSLANDMUSEUM
TABLE i.Charactermainx, DistributioniaffileKeycharacterstatesamongtaxaAbbrevialion.Ms=nntofspecies
examined ingroup n -nr, ofspecimens, polymorphiccharactersshown: Pseud.Pseudemvdura; EldlElseyu
latisiernum group, Elus, Elusor, Rhco, Rheodyres, Else, Eiseya dentata group, Elno, Eiseya novaegiuneae;
EQld, Queensland Eiseya group; F.liiv, Eiseya Iavarackorum (holotype):Emyd,Entydum.
Ulu^i•-- I Eise(s=2j Elno(s=l) EQWts=3) EfeV(Bsl) Emydc^4i
(n=lO»
i 111,-,. , , \ n (' i f I I 1 !
CharacterB i i I 2 .1 3 i 2 4
Chftraco r u u (t ') 1 I I 1 I
CharacterD 1 i 1 I 2 T T 5 1
Cttfirflcterf. rii '.' i. n 1 1 n
a first vertebral scute that was markedly wider Emydura Iavarackorum possesses all ck
lhan vertebral* 2 and 3; and nocervical scute. lers that are consistent across species of the
A significant feature of Emydura lav- Eiseyadentata generic group (Table I)and. more
nnti'kornw, though difficult to quantify, was an significantly, all characters uniquely possessed
indentation ofthe jarapace margin in thearc by the Queensland Eiseya dentata 5tfb-gjt>Up
ihe cervical deft and first marginal scutes. This (Table Ij- Of those characters which separate
feature is held in common with turllcs in the Emydura fromthe Eiseyadentata generic group,
Eiseya laiisternum group and Pstud&nydHrctt IS the fossil consistently possessed character states
variable among the Queensland forms ofEiseya which distinguished it fromEmydura. Therefore,
dentata, and neverpresent in the Northern Terri WC assign Emydura Iavarackorum to the genus
lOTJI and NewGuineaformsofEiseyadematanor Else\a as EiseyaIavarackorum(White&Airher,
in Elusor, Rlwodytcsand Emydura,Althoughnot 1994).
considered a useful characteratgeneric level, We Since the description atEiseya Iavarackorum,
will use tt in combination with other similarities specimens of ihe exuint Eiseya sp. (Nieholson
10establishaclQW relationshipbetweenthe fossil drainage,Georges & Adams, 996) have become
Emydura Iavarackorum and an extant form of available. The two forms arc i1ndistinguishable in
Eiseya f/om the Nicholson River. everydiagnosticcharacter, including theindenta-
tion o\' the anterior margin of the carapace. A
DISCUSSION unique featureoftheNicholson population, when
onlyextant formsareconsidered, isthesigmoidal
The bridge carapace suture runs parallel and shape of the sulcus between the humerals and
adjacent to 'he tib/gomophosisis in speciesofthe pectorals on the plastron (Fig. 5C), this sulcus is
Eiseya laiisternum group, Pseudemydura and straight in all other species oftheEiseya dentata
Elusor and so can ^e clearly distinguished from generic group (Fig. 5E).This feature ispresent in
nilahatetteoftsoisRsoihiletoEhdemyyriidcbus/rgaaosrInaoapvphaoosrssaiic\bkiloseroluidmePnl(teTiuafrbialcleat1iIeo).lniRmloio-r dAtihrtecihohenoral,loft1oy9sps9ei4l)OsfapneEdciisimeneyoannsIenao(vwaQrMaa3vc0akiKol1arSbul)meo((fFWihtgihte5eDa)d&.-
Ihe fossil,leavingonly theElsevodentatageneric The anterior plastron is absent from the thud
group and Emydura as possibilities. fossil specimen (QM308I7).
Two sub-groups within the Eiseya dentata ge- In contrast, the fossil has strongly embossed,
neric group can be distinguished. The first com- rounded peripheral in the region adjacent i:i the
prises Eiseya dentata i senmi strielo), Eiseya bridge, a feature not present in the 15 specimens
anvrtryjuneae. Elsryabranderiwrsn, and Eiseya from the Nicholson population, This is a sirrulikl
sp. (Vogclkopf Region, PNG; Anders Khi f| condition to thai found in aged, adull individuals
pers comm) and Else\a sp. (South Alligator in a numberofspecies, i.e., individuals whichare
River, NT; Georges& Adams, 996), Thesecond large for their species, such as Elusor ntacmrus
1
sub group is restricted to Queensland (Queens- (specimens over 400mm). Eiseya sp. aff. E
land Eiseya dentata sub-group) and comprises dentata from the Burnett River (specimens over
Eiseya sp, {Nicholson). Eiseya sp. (Johnstone), 380mm) and Emydura sub^lahosa from the
and Eiseya sp. (Burnett) (Georges & Adams. Gregory and Reynolds Rivers (specimens over
I9%). Generic recognitionofthesesub-groups is 25Omm). We consider this trail to be essentially
not suggested, a feature of large a^vd specimens in a range of
IDENTIFICATION OFALIVINGFOSSIL
chelid turtles. Noneofthe lurtli allied from LITERATURECITED
the Nicholson drainage had carapace lengths in
uacsesa oJf320mrn, well below ihe maximum size CANN. J & LEGLER, J.M. 1994 The Mary River
fbrspecies in the L'tseya dentata generic group. lurttme: a newgenusandspeciesofshort-neckctl
from Queensland, Australia iTcstudmcv
Inspeciesleveltaxonomy,theonus isondiffer- Pleuro!dirat.CheionianConservationand Biology
ential diagnosis The shell of the fossil hololype 1(2): 81-96
is adcqualely preserved for diagnostic purp- COGGER,H.G.XAMERON,E.E.&COGGER. II.M.
We therefore propose thai, in the absence 6( any 1983, ZooI<igical CatalogueofAustralia, Volume
diagnosahle difference and the relatively young !, Amphibia and Repulia. (Australian Govern
age ofthe fossil material, Etseya tfivamcKdrum mem Priming Service: Canberra). 3l3pp,
and the Nicholson Elseyu sp. aff. E. dentara be GAFFNEY E.S. 1977. Tlic side-necked mnle family
rleivgianrgdefdossaislafsriensghlweatsepercituerst.leI,t aisnAeu.s\turmaltipa'ospuFliras-t Cdheerliivdeade:cvhaaratchteeorrsy. oAfmerreilactainonMshuispseuumsinNgovisthaatree.ds
tthiaotn aolfloaehPrloeniisetoscuebnsepetcaixeosn.beWreecdoognniostedp.ropose GEOR2G6E20S:,ia. ft ADAMS, M [902. A pfrylpgcnj Dl
Australian chelid turtles based on alio/ /HI
irophoresis. Australian Journal of Zooloy.v 40.
ACKNOWLEDGEMENTS 453-476.
19%, ElecifOphorcdcdelineation ot speciesbound-
Theauthorswouldlike tothankPatrickCoupcr arieswithintheshor^nccked freshwaterturtlesof
Australia (TcMudincv Chelidae). Journal of the
(Queensland Museum), Ross Sadlier (Australian
Linnean Society 8:24 -260
Museum), Paul Homer(Museum and Art Galler- LEGLER. J.M. 1981. T1h1etax1onomy,distribuiiw
ies oi' the Northern Territory) and Laurie Smith ecology ot Australian liesliwatct turtte:-- i i
•!Museum of Western Australia) for the loans or tudines*. Pleurodira: Chelidae). National I
Fossil and skeletal material and for access to the graphic Society Rescareh Reports 13; 391-4W
museum's turtlecollections; PeterWhitehead for THOMSON, S. & GEORGES. A. 1996 Neural bones
a large donationofmaterial stored at the Conser- in Australian the]id turtles. Chelonian Con
vation Commission of the Northern Territory; lionftodBiology 2(1 ): N.
JohnCann, John Legler and Gerald Kuehling for WHITE. A. & ARCHER, M. 1494 BUjtftfm
the loan ofmaterial fromtheirprivatecollections - a dm Pleistocene iwtk (Plsui
andthe DepartmentofEnvironmentandHeritage Chelidae! from fluvtanlc deposit* .u Rivet
Nnnhwesieni Queensland. Reeoids ol the Suiidi
in Queensland foi permits bo collect in ihe Ntch AustralianMuseum27; 159 167
oWlOsUolndDersapeicniaaglelyoflikneorltohilwinensktSQnumeemncslRaenydn.olWdes ZANGCEuiRuLs.,CK, BlcMi(lwai.rs,("h!e).tJu"nAi.c &shelPlf.flPSpO,BS,31T.1A-3.40(.ed&i)n
of the Universityol'Canberra forthe illustrations Biologv ot the RcptUia Vbl I. Morpholoj
m thispaptrand PeterOgilvie fpj the photography. iAcademic Press; London).
APPENDIXA 0303; Emvdura subglohosa: NTM5028, 820 M28.
Specimens Examined. All nftrue: tUHftd Ibi un- 13433, 16332, UC0171-72.0]/; Eww/jfffl I i
ucscrihed species Lire from George^ & Mams (1992, NTMI35I3-14, 32917, 32976, UC 0*165; Efceyrt sp
1996). Abbreviation.', used: AM, Australian Museum; aff. E.dentate(Burnett):UC0305-6. QM2966, 28449.
NTM. Museum and Art Galleries ofthe Northern Tfer- 36036, 36039, 36041-42. 36044-47, 37933. 38533,
, i , ,QM.QueenslandMuseum;waM.Western f n\ 59269-71; Etsexa sp. aff. £ dentaia (Johnstone):
Indian Museum-, UC, University of Canberra; UM, QM22694, 23175, 23299, 23300, 23322, 24
1 ;r It] i'1 Mu. in- i ii Id Scries: UL . I nfvi 28449,48060,4S068;Eisero sp. aff. £ cknta
uU1fU6WU31ut39s0n4.oh8i8Q,Mn5WW9^2E6t5x,rv5a9t2l7e7n-Ut88a04t.-o9:3UN,C0T3iM0r71-31381;9, E10l3354241,. AbNliTliMisg5ta0etr9ot7rw),; 1 A^MII\2S103rjQ9825,\,ML11C2208300004141;8,-F2.9Ql,sMe5xQa9Ms2p845aSfl02£M."
internum-, AMI23037, 123039, 125474-75, 48038; Elseya ftp. aff E. lartstemm [Bellinemij
QM48054-55; Etseya novaeguinwe- AM42662, AM1383S7-88, UM02016-I7. Elsnv sp aIT /.
125038; Ehtyu lavamckontM QMF24I21, F30S17- lalfsternm (Manning). AM123040, 123042, QM-
18 (fossil), QM31939, 31942. 31944, 31946-47, 59289-90;Emxdura sp.;ili'. E. vietariae(Dob% Missi nj
31949-50.3W5Z,46284,47908,47911,48544,48547, AMI25470-7I, 125491. NTM&2H, 8213, 17339;
60255, UCQ20I o*\i;ini ), Emydum macquarlii Pxsudcmvdura umbrma:^Ul Dl7t vVaM'-
QM48U16, 4S034. 48050-51.59275-76, UC0175-76, Hheodxttxtcukapr. i C01