The oldest South American silesaurid: New remains from the Middle Triassic (Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone) increase the time range of silesaurid fossil record in southern Brazil

The Triassic deposits of South America are key to understand the early radiation of Dinosauromorpha. Though the fossil record of the group is relatively abundant in Carnian- and Norian-aged strata from Argentina and Brazil, Middle Triassic dinosauromorphs are scarce, at least in the Brazilian record. In this contribution, we describe a set of fossils collected from a site biostratigraphically correlated to the Dinodontosaurus Assemblage Zone, which is regarded as Ladinian in age. Within the sample, we identified a single partial ilium with anatomical features consistent with Silesauridae. As a result, we propose a new taxon, Gamatavus antiquus gen. et sp. nov. as the first silesaurid from the Brazilian Middle Triassic. Biostratigraphic comparisons suggest the Dinodontosaurus Assemblage Zone to be older than the Argentinean Massetognathus-Chanaresuchus AZ, rendering the new specimen also the oldest South American silesaurid. This contribution adds to recent works that suggest biostratigraphical similarity between the Brazilian Dinodontosaurus AZ and the African Lifua Member and Ntawere Formation, from where the oldest dinosauromorph records are registered.