Abstract

The Late Cretaceous continental deposits of Ukhaa Tolgod, Mongolia, have yielded remains of a new Nanhsiungchelyid turtle, Zangerlia ukhaachelys, n.sp. This taxon is based on a single individual that consists of a partial cranium, representatives of all peripherals, an almost complete plastron, and limb fragments. Zangerlia ukhaachelys is diagnosed as a new taxon by the presence of an anteromedial process of the hyoplastron that reduces the typical contact of the entoplastron with the epiplastron. Phylogenetic analysis firmly places Zangerlia ukhaachelys as sister to Zangerlia testudinimorpha and Zangerlia neimongolensis within Nanhsiungchelyid and confirms the close phylogenetic relationships between Nanhsiungchelys wuchingensis and Anomalochelys angulata and among all North American representatives of Basilemys. In addition, there is modest support that all Asian representatives of Nanhsiungchelyid form a monophyletic clade, which is primarily diagnosed by a deep, triangular nuchal notch. From a biogeographic standpoint, it is evident that the Late Cretaceous faunas of Asia and North America are closely related; however, phylogenetic considerations demonstrate that faunal exchange was limited for the Nanhsiungchelyid.