ORYCTOS.Vol. 3 : 9 - 18.Décembre 2000 DESCRTPTIONOF TIIE SKULLOB POLYSTERNON PROVINCTAZE (MATIruRON, 1369) A SIDE.NECKEDTURTLE (PELOMEDUSOIDES : BOTHREMYDIDAE) FROMTHE LATE CRETACEOUS OF VILLEVEYRAC, FRANCE Haiyan TONG'and EugeneS. GAFFNEY, 'ResearchAssociate, Division of Paleontology,American Museum of NaturalHistory. Currentaddress : 16cour du Liégat,15013 Paris, France. '?Curator,Division of Paleontology,American Museum of NaturalHistory USA Abstract z Polysternon is a European side-neckedturtle based only on shell material. A skull found from the Late Cretaceousof Villeveyrac, Herault, France,is referred to this taxon becauseshells clearly belonging to Polysternon provinciale occur in the samebeds. The skull of Palysternon shows that it is a bothremydid with the quadrate-basis- phenoid covering the prootic ventrally, the eustachiantube separatedfrom the stapes,precolumellarfossa absent, condylus occipitalis consisting only of exoccipitals and an exoccipital-quadratecontact. Polysternon lies in the Bothremys-Groupbecause it has triangular, expandedtriturating surfaces,extensive exposure of the palatine on the triturating surfaces,and a supraoccipital-quadratecontact. Polysternon is most closely related to Foxemys. They possessa number of charactersin common including an open incisura columellae auris and a deep pterygoideus muscle concavity. Polysternon differs from Foxemysin having a broader midline, palatal depression,a narrower tri- turating surface with lower labial ridges, and a condylus occipitalis that is placed fanher posterior. Key words: pleurodire, Polystemon, bothremydid, Inte Cretaceous,France Description du crâne de Polysternon provinciale (Matheron, 1869), une tortue pleurodire @elomedusoides : Bothremydidae) du Crétacé supérieur de Villeveyrac (France) Résumé z Polysterno,nest une tortue pleurodire européennedécrite uniquement sur des restes de carapaces.Un crâne trouvé dans le Crétacêsupérieur de Villeveyrac, Hérault, France, est attribué à Polysternonprovinciale, dont des carapacesont été trouvées dans les mêmes niveaux. Le crâne de Polysternonmontre qu'il s'agit d'un bo'thre- mydidé d'après les caractèressuivants: carré-basisphénoidecouvrant le prootique venfralement, tube d'Eustache séparédu stapes,precolumellar fossa absent,condylus occipitalis formé seulementpar les exoccipitaux et contact exoccipital-carré.Polysternon est placé dansle groupe Bothremys à causede la surfacetriturante triangulaire et élar- gie, de la vaste participation du palatin à la surfacetriturante, et du contact supraoccipital-carré.Polysternon est par- ticulièrement proche de Foxemys par la possessionde nombreux caractèresen cofilmun comprenant une incisura columellae auris o'sverteet une dépressiondu pterygoide profonde. Polysternon diffère de Foxemyspar une dépres- sion palatale médiane plus large, une surfacetriturante plus étroite avec une crête labiale plus basse, et:etr-condylus occipitalis placé plus postérieurement. Mots clés : pleurodire, Polysternon, bothremydidé,Crétacé supérieur;France ORYCTOS,Vol.3,2000 INTRODUCTION include both the pleurodiran bothremydid Polysternonprovinciale and the cryptodiranSolemys. The genusPolysternon was erectedby Portis in The palaeoecologyof the vertebrate-bearingLate 1882 on the basisof a posteriorportion of shell from Cretaceousbeds of Villeveyrac has been reconstruc- the Late Cretaceousof the Fuveau basin, southeas- ted on the basis of sedimentologicaland paleontolo- tern France. Portis (1882) referred to the genus gical studies which indicate an estuarinelandscape Polysternonthe material (two shell fragmentsinclu- combining freshwater and brackish environments ding an anterior portion of carapace)from the same (seeBuffetavt et al.,1996). basin described as Pleurosternon provinciale by Although the Bothremydidaewas namedas early Matheron (1869). Unfortunately, Matheron did not as 1891by GeorgeBaur, the term fell into disusefor figure any specimen. The material described by most of this century and the few included taxa, parti- Portis (1882)is now housedin the MuséeCantonal cularly Bothremys and Taphrosphys,were simply de Géologie de Lausanne,Switzerland. In 1931, included in the Pelomedusidae.Antunes and Broin Nopcsa studied four turtle shells from the Late (1988) and Broin (1988) revived Bothremydidae, Cretacousof southernFrance in the Muséed'Histoire provided a new diagnosis and added taxa, such as Naturellede Marseille, andreviewed Matheron's and Rosasia, based on skulls. Recent papers on fossil Portis' material.He recognized Po ly s t e rnon ander ec- pleurodires such as Meylan (7996), Lapparent de ted a new genus,Elochelys, including two species,E Broin andWerner (1998), and Tong et aI. (1998),use major and E. perfecta (Nopcsa, l93I). Later, de the Antunes and Broin (1988) terminology in which Broin (1977). studied the Late Cretaceous and Bothremydidae,Podocnemididae, and Pelomedusidae Tertiary continental turtle faunas of France, and (restrictedto Pelusiosand Pelomedusa) are contained synonymizedElochelys major Nopcsa, 1931 and in the Pelomedusoides(which equalsPelomedusidae Polysternonprovinciale (Matheron, 1869).All these in the classicsense). Bothremydids are now realized are basedon shell material, the skull was, until very to be a more widespreadand diversegroup than pre- recently, unknown, Foxemys mechinorum (Tong et viously considered. al., 1998) was the first pleurodiran turtle from the Useful reviews of the literatureon bothremydids Late Cretaceousof southernFrance described on the can be found in Broin (1988) andAntunes and Broin basisof both skull and shell material.The turtle skull (1988). Previously describedbothremydid skulls are describedhere was collected by Mr Guy Costa. It as follows: Bothremys(Gaffney and Zangerl. 1968; was figured and referred to Polysternonprovinciale Gaffney, 1977), Taphrosphys (Gaffney, 1975), in Buffetaut et al. (1996) andLapparent de Broin and Rosasia(Antunes and Broin, 1988), Foxemys(Tong Werner(1998, fig. a). The identification of this skull et al., 1998), Zolhafa (Lapparent de Broin and as Polysternon provinciale is based solely on the Werner, 1998), Arenila (Lapparent de Broin and occurrenceof the skull in the same formation and rù/erner, 1998), and Nigeremys (Bergounioux and 'Werner, geographicregion as shells of P. provinciale. It is Crouzel, 1968; Lapparent de Broin and possiblethat further discoverieswill alter this provi- 1998).A generaltreatment and descriptionof pleuro- sional identification. Nonetheless,we feel that this dire skulls, turtle skull morphology and terminology, courseis preferableto naming a new taxon or to not and a literaturereview is in Gaffney (1979). identifying the skull at all.In any case,both skull and shellsare bothremydids. SYSTEMATICS The Villeveyrac quarriesare located about 20 km south-westof Montpellier (Hérault,France). The ver- Order TESTLJDINESLinnaeus tebrate fauna comes from the lower seriesof the Late SuborderPLEURODIRA Cope Cretaceousbeds, which are Lower Campaniandark Hyperfamily PELOMEDUS OIDES Cope clays. It includes fishes (Ginglymodi and Teleostei), Family BOTHREMYDIDAE B aur frogs, turtles, lizards, crocodilesand dinosaurs(the- POLYSTERNONPortis 1882 ropods, iguanodonts and ankylosaurs). Turtle Poly sternon provinciale (Matheron,1 869) remains are mainly abundant shell fragments ; they (Fig. 1-2) 10 TONG & GAIIFNEY - DESCRIPTIONOF TIM SKIJLL OF POLYSTERNONPROVINCIALE RevisedDiagnosis: Bothremydid pleurodire with pterygoideusmuscle concavity; differs from F oxemys the following bothremydidsynapomorphies: quadra- in having a broadermidline, palataldepression, a nar- te-basisphenoidcovers prootic ventrally, eustachian rower triturating surface with lower labial ridges, a tube separated from stapes, precolumellar fossa shallower pterygoideusmuscle concavity, a shorter absent,condylus occipitalis consistingonly of exoc- exoccipital midline contact, a wider and longer cipitals and exoccipital-quadratecontact; differs from basioccipital,and a more posteior condylusoccipita- all other bothremydids except Foxemys in having an /is; smoothtriturating surfaceas in Foxemysbut dis- open rather than closed incisura columellae auris; tinct from the pits seenin Bothremys,Rosasia, and skull agreeswith F oxemysbut differs ftom Ni geremy s Zolhafa: shell similar to Foxemysbut having a nuchal and Taphrosphysin being wedge-shapedwith a pos- emargination,a small intergular scale, and an acute teriorly expanded triturating surface; agrees with anal notch. Arenila and Foxemys in having a relatively deep Measurements: seeTable 1. Figure 1 Polysternon provinciale, Late Cretaceous, Mlleveyrac, France. Skull, A - dorsal view, B - ventral view, C - right lateral view, D - anterior view, E - Ieft lateral view, F - occipital view. 11 ORYCTOS,Vol.3,2000 DESCRIPTION ly. In ventral view, a small part of the medial process of the jugal is visible contactingthe maxilla anterior- Material : an isolated and nearly complete skull ly and the palatinemedially. without lower jaw (AE28, Costa Collection), collec- The right quadratojugalin AE28 is mostly mis- ted by Guy Costa in one if the Villeveyrac quarries. sing but the remaining portion shows its contacts SeeBuffetaut et al. (1996) for further locality data. with the postorbital,jugal, and maxilla. The left qua- Preservation : The skull is almost complete but dratojugal is completebut much of it is broken and slightly crusheddorsovenffally; the right otic region disturbed by cracks. As preserved it agrees with and the middle of the palate are damaged.Al1 the Foxemys in