New Genus and Species of Silesaur Unearthed in Brazil

November 24, 2023

Paleontologists from the Federal University of Santa Maria have discovered a new genus and species of silesaur, naming it Amanasaurus nesbitti. This ancient creature lived in what is now Brazil during the Carnian age of the Late Triassic epoch, approximately 233 million years ago.

Silesauridae: Extinct Family of Dinosauriform Reptiles

Amanasaurus nesbitti belonged to the extinct family of Triassic dinosauriform reptiles known as Silesauridae. These reptiles are characterized by their fairly long necks and legs, possibly exhibiting quadrupedal habits. Silesaurids are considered a group of non-dinosaur dinosauriforms and are often regarded as the sister group of dinosaurs.

Ecological Niches and Evolutionary Relationships

Silesaurids occupied various ecological niches, with early species being carnivorous and later ones adapting to specialized herbivory. Notably, they are of particular interest due to their close phylogenetic relationships with dinosaurs, with some studies suggesting silesaurs as the closest evolutionary relatives of dinosaurs.

Fossil Discoveries and Size Comparisons

The researchers examined bone fragments, including portions of the right and left femurs of Amanasaurus nesbitti, found at the Pivetta site in Brazil. The discovery challenges previous notions about the size of silesaurs compared to early dinosaurs, suggesting that Amanasaurus nesbitti rivaled early dinosaurs in size. This finding adds complexity to the understanding of the radiation of Pan-Aves during the Triassic period.

Implications for Evolutionary Models

The discovery challenges existing models, as silesaurs, irrespective of their phylogenetic position, persisted throughout most of the Triassic period. The plesiomorphic body size of silesaurs during the dawn of dinosaurs contradicts the previous assumption of decreasing body size in silesaur lineages over time.

Conclusion: A Complex Scenario in Triassic Faunas

The study underscores the complexity of Triassic faunas, highlighting the need to reassess existing models based on new fossil evidence. Amanasaurus nesbitti provides valuable insights into the evolutionary dynamics of silesaurs and their role in the early stages of Earth’s diverse reptilian inhabitants.

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