Phylogenetic relationships of the Bauru Group turtles (late Cretaceous of south-central Brazil)

No chelonian of the Bauru Group (Late Cretaceous of south-central Brazil) has so far been included in a numerical cladistic analysis with an explicit taxon-character data matrix. Out of the five taxa formally described from that stratigraphic unit, those based on more complete specimens - Bauruemys elegans, Cambaremys langertoni, and Roxochelys wanderleyi - were considered in a cladistic study of the pro-Podocnemidae Pelomedusoides. The resulting hypothesis of relationships places the specimen known as FR-4922 and Brasilemys josai among Pelomedusoides basal to Podocnemoidea. Within that clade, the Bauru Group taxa lie basal to Podocnemidae. Roxochelys is revealed to be a monophyletic genus, closer to Podocnemidae than the other analyzed Cretaceous forms. Among these, Bauruemys elegans is more derived than Portezueloemys patagonica, while the position of Cambaremys langertoni is ambiguous. Within extant Podocnemidae, a sister group relationship between Peltocephalus dumerilianus and Erymnochelys madagascariensis is proposed.