Bridging the gap: Sphenodont remains from the Turonian (Upper Cretaceous) of Patagonia. Palaeobiological inferences

Abstract

Rhynchocephalians are a lepidosaur clade with a single living species. Here we report the first record of an eilenodontine sphenodontian from Turonian beds in South America. The new Turonian basal eilenodontine sphenodontian, Patagosphenos watuku gen. et sp. nov, is described. The specimen is represented by partial cranial and postcranial remains, being very similar to other eilenodontines such as Kaikaifilusaurus and Eilenodon. Moreover, the genus Kaikaifilusaurus is reported for the first time from Turonian beds. Furthermore, this genus is revalidated, being previously considered as a nomen dubium. Paleohistological analysis of Patagosphenos gen. nov reveals a similar bone microstructure to that of the living Sphenodon. We infer that physiological adaptations to survive in cold (freezing conditions) environments may constitute the key pre-adaptation that allowed Sphenodon to survive the Cretaceous-Palaeogene boundary.