Archosauriform remains from the Lower Triassic Sanga do Cabral Formation of Brazil

ABSTRACT

Early Triassic archosauriform remains are often related to the Proterosuchidae and the Erythrosuchidae, common stem-archosaurs in the aftermath of the end-Permian extinction event. South American proterosuchid remains are rare, with only a few specimens from the Lower Triassic Sanga do Cabral Formation briefly mentioned in literature. The Lower Triassic Sanga do Cabral Formation has a growing fossil record, thus far composed of procolophonids, temnospondyls, and early-branching archosauromorphs. In this work, new materials referred to cf. Chasmatosuchus and cf. Proterosuchus (Archosauriformes) are described, representing the first conclusive archosauriform records from the Lower Triassic of Brazil. Proterosuchids are among the stratigraphically oldest Archosauriformes, with their earliest unambiguous occurrences coming from the uppermost Permian of Russia. This clade is widely spread among well-explored Lower Triassic formations, flourishing during the recovery phase from the end-Permian mass extinction. The presence of non-archosaurian archosauriforms in southwestern Gondwana reinforces the rapid diversification of archosauromorphs during the Early Triassic. The Sanga do Cabral Formation fossil assemblage is becoming important for understanding how the initial adaptive radiation of archosauromorphs took place.

ACKNOWLEDGMENTS

For allowing access to fossil collections, FLP is indebted to C. Klug (Paläontologisches Institut und Museum, Universität Zürich), R. Schoch (Naturkunde Museum Stuttgart), O. Rauhut and M. Moser (Bayerische Staatssammlung für Paläontologie und Geologie), M. Norell and C. Mehling (American Museum of Natural History), S. Chapman and L. Steel (Natural History Museum), B. Zipfel and B.E. Rubidge (Evolutionary Studies Institute, University of Witwatersrand), Z. Skosan and C. Browning (Iziko South African Museum). M. Ezcurra, B. Peecook and editor H.-D. Sues are acknowledged for their thorough revisions of an early version of this manuscript. We also thank A. Dias for helping to translate the Russian bibliography. This study was financed by grants from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq 407969/2016-0; 305758/2017-9; 316811/2021-1 to FLP; 309414/2019-9, 422568/2018-0 to LK), Fundação de Amparo à Pesquisa do Estado do RS (21/2551-0002030-0 to LK) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES finance code 0001 to TMO).