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.

南美洲的三叠纪沉积物是了解恐龙恐龙早期辐射的关键。尽管该群的化石记录在阿根廷和巴西的卡尼纪和诺里纪地层中相对丰富，但中三叠纪恐龙类恐龙却很少，至少在巴西的记录中是这样。在这篇文章中，我们描述了一组从生物地层相关的地点收集的化石，该地点与恐龙组合区相关，该组合区被认为是拉丁时代。在样本中，我们确定了一个具有与 Silesauridae 一致的解剖特征的部分髂骨。因此，我们提出了一个新的分类单元，Gamatavus antiquus gen。等人。十一月 作为巴西中三叠纪的第一只龙目。生物地层比较表明Dinodontosaurus Assemblage Zone 比阿根廷的Massetognathus - Chanaresuchus AZ 更古老，这使得新标本也是南美最古老的silesaurid。这一贡献增加了最近的工作，这些工作表明巴西恐龙 AZ 与非洲 Lifua 成员和 Ntawere 组之间的生物地层相似性，从那里记录了最古老的恐龙形态记录。