Old fossil findings in the Upper Triassic rocks of southern Brazil improve diversity of traversodontid cynodonts (Therapsida, Cynodontia)

Abstract

In this contribution we describe a new genus and species of gomphodontosuchinecynodont from the Late Triassic Hyperodapedon Assemblage Zone (AZ)of the Santa Maria Supersequence of southern Brazil, based on material collected20 years ago. The new taxon, Santagnathus mariensis gen. et sp. nov., isbased on numerous cranial and postcranial remains, which altogether providedata on several parts of the skeleton. Santagnathus mariensis is closely relatedto Siriusgnathus niemeyerorum and Exaeretodon spp. and expands the knowledgeabout gomphodontosuchine cynodonts. Morphologically, the new specieshas a skull bauplan particularly similar to S. niemeyerorum andE. riograndensis, differing from them by a unique combination of traits such asthree upper incisors, the absence of a descending process in the jugal, a moreposterior position of the postorbital bar and a preorbital region larger than thetemporal one. The new traversodontid was found associated with the rhynchosaurHyperodapedon sp., corroborating the assignment of the cynodont fossilsto the Hyperodapedon AZ. We also provide comments on the status of theArgentine traversodontid cynodont Proexaeretodon vincei, typically considereda junior synonym of Exaeretodon argentinus, and here accepted as a validtaxon.