Pareiasaurids from the Rio do Rasto Formation, Southern Brazil: biostratigraphic implications for Permian faunas of the Paraná Basin

Abstract

Comparison between pareiasaurid materials from Acegu�, originally assigned to Pareiasaurusamericanus, and a new cranium from Posto Queimado indicates that they belong to the same taxon. Despite theirsize difference, the skulls from these localities show similarities in the maxillary dentition and dermal boneornamentation. Dental and cranial characters confirm the difference between the Brazilian pareiasaurid and theSouth African Pareiasaurus, supporting the proposed allocation of the Brazilian form in the genusProvelosaurus. The Brazilian pareiasaurid has autapomorphies in the shape of the squamosal and themorphology and placement of the quadratojugal bosses. The presence of the same pareiasaurid in PostoQueimado and Acegu� strongly indicates that these faunas are contemporaneous. The record of dinocephaliansand pareiasaurids in Posto Queimado suggests a correlation of the Posto Queimado-Acegu� assemblage with theGuadalupian Tapinocephalus Assemblage Zone of South Africa and Isheevo Assemblage of Eastern Europe.The presence of amphibians tentatively assigned to archegosaurids at Acegu� fauna however, represents aconflict because the last global record of this family is known from the Ocher fauna from Eastern Europe, whichis regarded older than the South African Tapinocephalus Assemblage Zone. Finally, the identity of fragmentaryremains from the Brazilian Early Triassic assigned to pareiasaurids, is questioned.