Ceratophrys sp. (MLP 88.V.20.1) from the north of the city of Mar del Plata, Buenos Aires, Argentina (Mercadal de Barrio & Barrio 2002)

A nearly complete skull and left mandible (MLP 88.V.20.1) was collected 1 km north of Mar del Plata (Fig. 1, locality 8) in sediments attributed to the Pleistocene Miramar Fm. (Cione & Tonni 2005; Marshall et al. 1984. These remains were identified as Ceratophrys sp. by Mercadal de Barrio & Barrio (2002).

Osteological features. The morphology of both elements resembles that of all Ceratophrys . The well-ossified skull (Fig. 5X, Y) is ornamented but lacks crests. The premaxillae and the posterolateral parts of both maxillary arcades and their suspensory elements are not preserved; thus general cranial proportions cannot be assessed. The squamosal otic plates are subquadrangular, and do not project posterior beyond the level of the occipital condyles (Fig. 5X). No teeth are completely preserved. The vomers seem to bear true teeth (Fig. 5Y). The lateral margins of the pterygoids are broken; thus, the presence/absence of the ventral process could not be determined. The mandibular bones, including the mentomeckelian bone, are fused one to one another (Fig. 5Q). A robust anterior fang is formed by elaboration of both the dentary and mentomeckelian. The dentary is higher than the angulosplenial, protuding from the dorsal margin of this later as a sharpened lamina of bone (Fig. 5Q).

Remarks. MLP 88.V.20.1 possesses all the proposed or possible synapomorphies of Ceratophryidae (exostosis, maxilla-squamosal contact, parieto-squamosal arch, expanded squamosal otic ramus overlapping prootic, pars palatina absent on anterior maxilla, spur-like fang formed by mentomeckelian and dentary, mentomeckelian and dentary fused) and Ceratophrys (robust, bar-shaped maxillary processes of nasal, postorbital fenestra) that can be evaluated in the preserved elements. Thus, the generic assignment is justified. Because MLP 88.V.20.1 has a combination of characters that might be plesiomorphic (discussed above), it cannot be assigned to a species of Ceratophrys .