Sítio paleontológico Cerro Chato: uma excepcional assembleia fóssil para o permiano brasileiro

Abstract

The Cerro Chato outcrop (Paraná Basin), Dom Pedrito municipality, Rio Grande do Sul State, Brazil, reveals a diverse fossil assemblage that includes sphenophytes, lycopsids, pteridosperms and gymnosperms, in addition to fish scales and molluscs. Because it reveals an associoation between well-preserved plant and animal specimens, this assemblage is unique among Rio do Rasto Formation deposits. The Cerro Chato outcrop, discovered in the 1950s and its location unknown since then, is recognized as a unique paleontological site for the study of flora from the Permian period. The flawed georeferencing, together with the disuse of dirt roads, led to a long lack of knowledge of the precise location of the site, making it impossible to develop studies on its fossil content beyond the preliminary research on specimens collected in the middle of the last century. The rediscovery of the site, in 2019, reopened unique opportunities for the resumption of scientific research on the fossil assemblage preserved in the site. Exploratory field surveys carried out in recent years have revealed a paleontological productivity that exceeds expectations, demonstrating a rare association of elements belonging to the Glossopteris Flora, with specimens that stand out for their abundance and excellent preservation. This work aims to investigate the paleontology of the Cerro Chato outcrop, conducting stratigraphically controlled excavations and presenting the occurrence of a new phytofossil taxon, thus far not recorded in Rio do Rasto Formation deposits from Rio Grande do Sul state. The abundance and quality of the specimens already recovered make the site a potential Lagerstätte. The research developed here, in addition to representing an expressive study, will serve as a basis for future research on the Permian paleoflora of Gondwana, filling gaps that still persist in the biodiversity of this important interval in Earth's history.