New specimen of Basilemys praeclara Hay and its bearing on the relationships of the Nanhsiungchelyidae (Reptilia: Testudines)

Abstract

A new specimen of the Cretaceous trionychoid turtle Basilemys praeclara Hay, from the Frenchman Formation (Upper Maastrichtian) of Saskatchewan, confirms the validity of the species, previously known only from the type specimen. Basilemys praeclara is considered the sister taxon of Basilemys sinuosa, and the restriction of this clade to the late Maastrichtian reinforces the distinctiveness of the Lancian chelonian fauna from the older Judithian chelonian fauna. Basilemys, Nanhsiungchelys, and Zangerlia comprise the family Nanhsiungchelyidae, with Basilemys and Nanhsiungchelys being sister taxa within the family.