PIPID FROGS FROM THE UPPER CRETACEOUS OF IN BECETEN, NIGER

A vertebrate assemblage from the Coniacian-Santonian Ibeceten Formatio n of southern Niger includes pipid frogs, which are described herein. The fossils occur within fluviatile-lacustrine strata and consist of d isarticulated elements. Two pipid taxa are present: the hyperossified Pachybatrachus taqueti gen. et sp. nov., and another unidentified taxo n. The phylogenetic relationships of both are discussed in the context of recent hypotheses of pipid evolution. Pachybatrachus exhibits some derived features unknown in other pipids. These include supplementary accretion of bone on the atlantal centrum, which is involved in an ad ditional articulation with the skull, as well as on the ventral surfac e of other vertebral centra. Following cladistic analysis, it is propo sed that Pachybatrachus is a pipine closely related to the living Afri can forms Hymenochirus and Pseudhymenochirus. The presence of the prim itive state for some hymenochirine synapomorphies suggests that Pachyb atrachus is their sister taxon. The relationships of the unidentified taxon remain equivocal owing to the fragmentary condition of available remains.