New postcranial remains of a non-mammaliaform cynodont from the Pinheiros-Chiniquá Sequence (Middle-Upper Triassic), Brazil

Abstract

The Pinheiros-Chiniquá Sequence (Dinodontosaurus Assemblage Zone, Middle/Upper Triassic) of the Santa Maria Supersequence in Brazil is renowned for its rich fossil record of traversodontid and probainognathian cynodonts (Therapsida: Eucynodontia). However, despite this diversity, their postcranial anatomy remains poorly studied. In this study, we describe new postcranial remains assigned to an eucynodont from this sequence. The specimen includes three presacral vertebrae, the proximal region of the left humerus, the proximal region of the left ulna, right and left femora. The absence of associated cranial material limits a definitive taxonomic assignment. Nonetheless, the combination of distinct femoral characteristics—(i) femoral head positioned well above the greater trochanter, (ii) greater trochanter laterally protruding with a distal projection (forming a “hook”), (iii) slender diaphysis, and iv) lesser trochanter oriented posteromedially—suggests affinities with traversodontids. Future discoveries of cranial material associated with similar postcranial remains could provide critical insights, helping to clarify the taxonomic identification of this specimen.