Fossil remains of a previously unknown species of reptile that lived about 250 million years ago (Triassic period) have been found in the Brazilian state of Rio Grande do Sul.

The reptile, named Teyujagua paradoxa, lived just after the great Permo-Triassic mass extinction event that occurred 252 million years ago.

This extinction wiped out about 90% of all species then living and was probably triggered by giant and intense volcanic eruptions in what is now Siberia.

The exceptional fossil skull of Teyujagua paradoxa was found in a Triassic rock exposure near the city of São Francisco de Assis.

According to Dr. Felipe Pinheiro from the Universidade Federal do Pampa, this fossil is very different from other fossils from the same age.

Its anatomy is intermediate between the primitive reptiles and an important group called Archosauriformes (archosauriforms).

“Dinosaurs, crocodilians, birds, pterosaurs and their close relatives all belong to the clade Archosauriformes, an extraordinarily diverse group that dominated terrestrial tetrapod faunas worldwide for nearly the entire Mesozoic Era, around 175 million years, and plays a major role in the modern biota, with birds comprising around a third of extant tetrapod biodiversity,” Dr. Pinheiro and co-authors explained in a paper in the journal Scientific Reports.

“However, the origins of this clade and its extraordinarily successful body plan remain obscure.”

“We describe an exceptionally preserved fossil skull from the Lower Triassic of Brazil, representing a new species, Teyujagua paradoxa, transitional in morphology between archosauriforms and more primitive reptiles.”

Teyujagua paradoxa was a small, quadrupedal reptile. The species grew up to about 5 feet (1.5 m) in length and lived in the margins of lakes and rivers, hunting amphibians and procolophonids — extinct, small bodied reptiles similar to lizards.

Its teeth were recurved with fine serrations and sharply pointed, indicating a carnivorous diet.

The nostrils were placed on the upper part of the snout, a typical feature of some aquatic or semi-aquatic animals, such as modern day crocodiles.

“Teyujagua paradoxa is a really important discovery because it helps us understand the origins of archosauriforms,” said co-author Dr. Richard Butler from the University of Birmingham, UK.

“Archosauriforms are spectacularly diverse and include everything from hummingbirds and crocodiles to giant dinosaurs like Tyrannosaurus rex and Brachiosaurus.”

“Teyujagua paradoxa fills an evolutionary gap between archosauriforms and more primitive reptiles and helps us understand how the archosauriform skull first evolved,” he said.

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Felipe L. Pinheiro et al. 2016. An exceptional fossil skull from South America and the origins of the archosauriform radiation. Scientific Reports 6, article number: 22817; doi: 10.1038/srep22817