New material of Procolophon (Parareptilia: Procolophonoidea) from the Lower Triassic of Brazil, with remarks on the ages of the Sanga do Cabral and Buena Vista formations of South America

We describe a large, fragmentary procolophonid skull and three large vertebrae from the Sanga do Cabral Formation, Paraná Basin, Lower Triassic of Brazil. Cranial and dental morphology allow us to refer the skull to the genus Procolophon; the fragmentary nature of the specimen, however, does not permit identification to species. The vertebrae are tentatively assigned to Procolophon. They are of a size expected for an individual represented by the skull, although the cranial and postcranial elements were not directly associated. The vertebrae are unusual for a procolophonid in exhibiting neural arches that are twice as broad as they are long, a dimension seen elsewhere among parareptiles only in pareiasaurs. A comparison of the manner of tetrapod preservation between the Sanga do Cabral and Katberg formations reveals that tetrapods in the former occur within conglomerates, whereas in the latter they are recovered mainly from mudstones. This taphonomic disparity may account for the absence in South America of the nearly cosmopolitan synapsid Lystrosaurus. The recent recognition of Permian tetrapods from the Buena Vista Formation of Uruguay, regarded widely to be a lateral equivalent of the Sanga do Cabral Formation, is assessed. We conclude that there is no compelling evidence of Permian tetrapods from the Buena Vista Formation and that the available information is suggestive of an Early Triassic age for that formation.