PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3397, 13 pp., 5 ®gures, 1 table March 27, 2003 Side-Necked Turtle Lower Jaws (Podocnemididae, Bothremydidae) from the Late Cretaceous Maevarano Formation of Madagascar EUGENE S. GAFFNEY1 AND CATHERINE A. FORSTER2 ABSTRACT Two lower jaws from the upper part (early Maastrichtian) of the late Cretaceous Mae- varano Formation in the Mahajanga Basin, northwestern Madagascar, are identi®ed as belonging to side-necked turtles (Pleurodira). A nearly complete lower jaw is identi®ed as cf. Erymnochelys because of its close resemblance to the living Malagasy Erymnochelys madagascariensis. Both uniquely possess the combination of a posteriorly directed pro- cessus retroarticularis and a nearly identical triturating surface that is narrow anteriorly with a horizontal labial ridge and a dorsally rising lingual ridge. A second specimen, consisting of an incomplete symphyseal region, is questionably identi®ed as Bothremy- didae on the basis of a thick wedge-shaped symphysis with partial or complete pits on the rami. The cf. Erymnochelys specimen is the oldest record of Erymnochelys or a taxon very similar to it, and it indicates the persistence of a Mesozoic element in the extant Malagasy turtle fauna. The possible bothremydid jaw suggests a more cosmopolitan element now extinct. 1 Curator, Division of Paleontology, American Museum of Natural History. e-mail: [email protected] 2 Department of Anatomical Sciences, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, NY 11794. e-mail: [email protected] Copyright q American Museum of Natural History 2003 ISSN 0003-0082 2 AMERICAN MUSEUM NOVITATES NO. 3397 INTRODUCTION from Antunes and Broin (1988) and Lappar- ent de Broin and Werner (1998). In Antunes In 1896, Charles DepeÂret reported numer- and Broin (1988: 179) the Betioky material ous indeterminate turtle carapace and plas- was referred to as consisting of a ``portion tron fragments collected in northwestern de carapace sans les parties anteÂrieure et pos- Madagascar from sediments that are now teÂrieure, conforme aÁ Bothremys ...''.Weare known as the Maevarano Formation. Seven- unaware of characters in the carapace unique ty-eight years later, in 1974, a team of French to the Bothremydidae, despite assertions to paleontologists returned to northwestern the contrary (Lapparent de Broin and Werner, Madagascar to conduct ®eldwork in the Mae- 1998). varano Formation near the village of Beri- Although turtle remains have been known votra, the same general area where DeÂperet's from the Maevarano Formation in the Beri- material was collected (Russell et al., 1976). votra region for more than one hundred Russell et al. (1976) collected material they years, their identi®cations remain largely un- identi®ed as a species of pleurodire, an iden- determined, and none have been ®gured or ti®cation based on numerous carapace frag- described to date. A series of recent expedi- ments, vertebrae, a cranial fragment, and a tions to the Maevarano Formation by the limb bone. Ravoavy (1987), in a summary of State University of New York at Stony Brook known fossils from the Maevarano Forma- and the Universite d'Antananarivo, begin- tion, was more speci®c and reported turtles ning in 1993, have recovered a diverse ver- of the family Pelomedusidae, but Ravoavy tebrate assemblage that includes birds, croc- did not speculate on the number of taxa pre- odilians, dinosaurs, freshwater ®shes, mam- sent. mals, snakes, frogs, and turtles (e.g., Krause Recently, Lapparent de Broin (2000) sum- et al., 1999). This additional turtle material marized all known fossil turtles from Mad- includes partial and fragmentary carapaces agascar, listing two occurrences of Creta- and plastra, cervical vertebrae, girdle and ceous pleurodires on the island, the only pre- limb elements, and fragmentary cranial ma- Holocene turtle record from the island: (1) terial. At least two, and probably more, pleu- Berivotra (Mahajanga area) of ``Senonian rodire taxa are represented in this material. age'', and (2) Betioky (near the Menarandroy Despite a virtual pavement of carapace and River in southwestern Madagascar) of ``Cen- plastron fragments at several sites in the omanian age''. The ®rst locality refers again Maevarano Formation, more complete spec- to the Maevarano Formation and to the spec- imens remain elusive. In this paper we de- imens previously collected and reported by scribe two new, distinct turtle taxa based on Russell et al. (1976). However, Lapparent de lower jaw material. Broin was more speci®c and refers the Mae- Both specimens described here were col- varano turtle material to ``Bothremydidae in- lected in 1996 from the Maevarano Forma- det., form B'' (Antunes and Broin, 1988). tion near the village of Berivotra, Mahajanga Antunes and Broin (1988: 180) reported Basin, northwestern Madagascar (see ®g. 2 ``Bothremydidae indetermineÂ, forme B'' as in Krause et al., 1999). Although the age of consisting of a ``portion de craÃne avec les the Maevarano Formation was reported as ei- carreÂ, opisthotique et prootique partiels, ther Cenomanian (e.g., Antunes and Broin, montrant une structure de la region otique 1988) or Campanian (e.g., Russell et al., caracteÂristique des bothremydideÂs et confor- 1976), recent stratigraphic work con®rmed me aÁ celle de Bothremys et Rosasia ...''. that the formation is younger than previously Although noted in various lists (Broin, 1988; surmised (Rogers et al., 2000). Both speci- Lapparent de Broin and Werner, 1998), none mens described here are from the highly fos- of this material has been described or ®g- siliferous upper members of the Maevarano ured, leaving the justi®cation for the identi- FormationÐthe Anembalemba and Miadana ®cations unknown. MembersÐwhich are regarded as early At the Betioky locality, Lapparent de Maastrichtian, and possibly late Maastrich- Broin identi®ed ``Bothremydidae indet., tian in age (Krause et al., 1999; Rogers et al., form A (? Bothremys)'' based on information 2000). 2003 GAFFNEY AND FORSTER: SIDE-NECKED TURTLE LOWER JAWS 3 A review of turtle lower jaw anatomy ex- and most of both prearticulars (®gs. 1, 2). plaining and illustrating the terms used here Collected by C.A. Forster. can be found in Gaffney (1979). Pleurodire LOCALITY: MAD 93±35, Berivotra region, jaws are not well represented in the literature, Mahajanga Basin, northwestern Madagascar. but Fuchs (1931) provided good descriptions HORIZON AND AGE: Anembalemba Mem- of Podocnemis. The taxonomy of pleurodires ber, Maevarano Formation, Maastrichtian. used here, recognizing Bothremydidae, Po- docnemididae, and Pelomedusidae, has been DESCRIPTION developed in recent years. Antunes and Broin (1988) and Broin (1988) revived Bothremy- DENTARY didae, provided a new diagnosis, and added The dentaries of FMNH PR 2231 are fused taxa, such as Rosasia, based on skulls and completely on the midline as in all other po- shells. Recent papers on fossil pleurodires, docnemidids and bothremydids (®gs. 1, 2). such as Meylan (1996), Lapparent de Broin Although there is a crack on the midline, there and Werner (1998), and Tong et al. (1998), is no sign of a suture anywhere on the sym- use the Antunes and Broin (1988) terminol- physis as seen in Pelomedusa and Emydura. ogy, in which Bothremydidae, Podocnemi- The symphysis is relatively long as in Erym- didae, and Pelomedusidae (restricted to Pe- nochelys, Peltocephalus, Podocnemis, and lusios and Pelomedusa) are contained in the bothremydids, but shorter than in most pelo- Pelomedusoides (which equals Pelomedusi- medusids. Peltocephalus differs from all other dae in the classic sense). Bothremydids are living podocnemidids and from bothremydids now recognized as a more widespread and diverse group than previously considered. in having a high, protuberant symphyseal pro- jection; this projection is also absent in INSTITUTIONAL ABBREVIATIONS FMNH PR 2231. The symphyseal tip of AMNH American Museum of Natural History, FMNH PR 2231 is broken, but the preserved New York portion indicates it was probably not pointed FMNH Field Museum of Natural History, Chi- as in the living Erymnochelys (®g. 3). cago The triturating surface in FMNH PR 2231 MNHN Museum National d'Histoire Naturelle, is relatively narrow at the symphysis (®gs. Paris 1A, 2A), as in Erymnochelys, in contrast to UA Universite d'Antananarivo, Antanana- the wider surface seen in Peltocephalus and rivo, Madagascar Podocnemis. There is no midline ridge as in ANATOMICAL ABBREVIATIONS some Recent Podocnemis species; rather, the ang angular midline is ¯at as in Erymnochelys and Pel- art articular tocephalus. The lingual ridge at the symphy- cor coronoid sis forms the upper margin for a concavity dent dentary that makes up most of the symphyseal re- f. aur foramen nervi auriculotemporalis gion. The concavity is broadly triangular f. dfm foramen dentofacialis majus with its apex pointing anteriorly. This mor- f. pct foramen posterius chorda tympani phology is similar to that of Erymnochelys, fm fossa meckelii although the concavity in FMNH PR 2231 is pra prearticular sa surangular somewhat wider and the curved apex less scm sulcus cartilaginis meckelii acute. This region is also similar to that in the bothremydids Cearachelys (Gaffney et SYSTEMATICS al., 2001a) and Kurmademys (Gaffney et al., ORDER TESTUDINES LINNAEUS, 1758 2001b). The left and right dentaries meet at SUBORDER PLEURODIRA COPE, 1864 a more obtuse angle in FMNH PR 2231 than HYPERFAMILY PELOMEDUSOIDES COPE, 1868a in Erymnochelys, Peltocephalus,orPodo- FAMILY PODOCNEMIDIDAE COPE, 1868b cnemis, and are more similar to bothremy- cf. Erymnochelys dids in this feature. In bothremydids similar to FMNH PR 2231 (i.e., Cearachelys and SPECIMEN: FMNH PR 2231; a nearly com- Kurmademys), the inner margin of the tritu- plete lower jaw, lacking the anteriormost tip rating surface is slightly S-shaped, while in 4 AMERICAN MUSEUM NOVITATES NO. 3397 Fig. 1. Photographs of the lower jaw of cf. Erymnochelys, FMNH PR 2231. A, Dorsal view; B, ventral view; C, anterior view; D, right lateral view; E, medial view of right jaw; and F, medial view of left jaw.