Biostratigraphic reappraisal of the Lower Triassic Sanga do Cabral Supersequence from South America, with a description of new material attributable to the parareptile genus Procolophon

DIAS-DA-SILVA, SÉRGIO; PINHEIRO, FELIPE L.; STOCK DA-ROSA, ÁTILA AUGUSTO; MARTINELLI, AGUSTÍN G.; SCHULTZ, CESAR L.; SILVA-NEVES, EDUARDO; MODESTO, SEAN P.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2017 vol. 79 p. 281 - 296

0895-9811

The Sanga do Cabral Supersequence (SCS), comprises the Brazilian Sanga do Cabral Formation (SCF) and the Uruguayan Buena Vista Formation (BVF). So far, the SCS has yielded temnospondyls, parareptiles, archosauromorphs, putative synapsids, and a number of indeterminate specimens. It is well stablished that the SCF is Early Triassic mainly due to the overall presence of the widespread Gondwanan reptile Procolophon trigoniceps. Conversely, the age of the BVF is subject of great controversy, being alternatively regarded as Permian, Permo-Triassic and Early Triassic. The BFV has yielded the definite procolophonid Pintosaurus magnidentis. Procolophonoidea is one of the the most diverse and conspicuous terrestrial tetrapod groups of the Lower Triassic Lystrosaurus Assemblage Zone (LAZ) in the Karoo Basin of South Africa, which preserves tetrapods from the aftermath of the end-Permian extinction event. Based on a previous interpretation that the fauna of the BVF is Permian, and in the reinterpretation of disarticulated vertebrae from SCF with ?swollen? neural arches as belonging to either seymouriamorphs or diadectomorphs, it was recently suggested that at least part of the SCF would be Permian in age, which prompted this comprehensive reevaluation of both SCS´s faunal content and geology. Moreoever, new, strikingly large procolophonid specimens (skull, vertebra and a mandibular fragment) from the Sanga do Cabral Formation are described and referred to the index Early Triassic genus Procolophon Also, the large procolophonid vertebra here described contradicts the alleged hypothesis that similar specimens previously studied belong to seymouriamorphs or diadectomorphs, as its morphology is consistent with that found in Procolophon. Despite the fact that so far the SCS lacks absolute dating, from a biostratigraphic perspective not a single diagnostic specimen even suggests the presence of Permian levels in this unit. Accordingly, all data reinforce the SCS´s Early Triassic age in this contribution, as all diagnostic and biostratigraphically significant paleontological content is either Early Triassic or restricted to Triassic.