Ceratophrys sp. (MLP 86.III.25.150–151) from the archeological locality Arroyo Tapalqué, Buenos Aires, Argentina (Mercadal de Barrio & Barrio 2002)

Two fragmentary specimens (MLP 86.III.25.150–151, Fig. 6 H–K) from the archeological locality Arroyo Tapalqué (Fig. 1, locality 2), in the Partido of Olavarría in the province of Buenos Aires were referred to Ceratophrys sp. by Mercadal de Barrio & Barrio (2002). This sequence dates to the middle Holocene (Fingini et al. 1998).

Osteological features. MLP 86. III.25.150 is a well-preserved right maxilla (Fig. 6I, J) and squamosal (Fig. 6H); although isolated, both elements articulate perfectly, indicating that they were from the same individual. The maxilla has a high, ornamented pars facialis (Fig. 6I), and lacks a distinct pars palatina in its anterior half (Fig. 6J). It bears a socket anterior to the level of the fourth tooth; presumably, the maxillary process of the premaxilla articulated with the maxilla via this socket. The fang-like teeth are monocuspid, with no evidence of a distinct crown and pedicel. The squamosal is nearly complete and heavily ornamented (Fig. 6H). The robust zygomatic ramus bears a lateral bony lamina that underlies the pars facialis of the maxilla when the elements articulate. The otic ramus is expanded in a subquadrangular plate that has an incomplete medial projection; the latter seems to correspond to the squamosal portion of a parieto-squamosal arch that would have delimited a postemporal fenestra.

MLP 86. III.25.151 consists of a pair of ornamented frontoparietals from one individual (Fig. 6K). Although disarticulated, the bone doubtless were medial contact in the living animal. Posteriorly, each frontoparietal has an oblique medial margin; this suggests that the bones were (at least partially) fused and broke as a result of disarticulation. Each bone has a lateral projection that seems to correspond to the frontoparietal part of the parieto-squamosal arch, which delimited a postorbital fenestra.

Remarks. Both fossils possess all possible synapomorphies of Ceratophryidae and Ceratophrys that can be evaluated on the preserved elements (MLP 86. III.25.150.—exostosis, non-pedicellate, monocuspid teeth, absence of pars palatina on anterior maxilla, maxilla-squamosal contact, parieto-squamosal arch [ Ceratophryidae], premaxilla with long maxillary process, postorbital fenestra [ Ceratophrys]; MLP 86. III.25.151.—exostosis, parieto-squamosal arch [ Ceratophryidae], postorbital fenestra [ Ceratophrys]). The generic assignment of these fossils to Ceratophrys is well supported, but the remains cannot be attributed to a species.