SAO JOAO DO POLESINE, Brazil — Scientists in Brazil announced the discovery of one of the world's oldest fossils believed to belong to an ancient reptile dating back some 237 million years that could help explain the rise of the dinosaurs.

Named Gondwanax paraisensis, the four-legged reptile species was roughly the size of a small dog with a long tail, or about one metre long and weighed between three kilogrammes and six kilogrammes, the scientists said in a statement on Monday (Oct 14).

The small reptile would have likely roamed the land of what is today southern Brazil, when the world was much hotter.

The fossil has been identified as a new silesaurid, an extinct group of reptiles. Palaeontologists debate whether silesaurids were true dinosaurs or possibly a precursor to the creatures that once dominated the Earth.

"Understanding the characteristics of these precursors could shed light on what was crucial for the dinosaurs' evolutionary success," the statement said.

Unearthed in a rock layer dating back to the Triassic period, between 252 million and 201 million years ago, the Gondwanax paraisensis fossil comes from the time when dinosaurs as well as mammals, crocodiles, turtles and frogs first arose.

In 2014, physician Pedro Lucas Porcela Aurelio found the fossil in the town of Paraiso do Sul in Brazil's southernmost Rio Grande do Sul state.

He donated it to a local university in 2021, kicking off three years of research.

"Being the first human to touch something from 237 million years ago is extraordinary," Aurelio told Reuters.

"It's an indescribable feeling," said the self-described palaeontology buff since childhood.

The discovery is detailed in an article by palaeontologist Rodrigo Temp Muller published late September in the scientific journal Gondwana Research.

"The most important part of this finding is its age," Muller said in an interview. "Because it's so old, it gives us clues as to how dinosaurs came to be."

He added that the remains were covered by a thick layer of rock when donated by Aurelio and initially only parts of the vertebrae were visible.

Gondwanax means "lord of Gondwana", referring to the Gondwana landmass in the southern region of the supercontinent Pangaea before the continents broke apart, while paraisensis honours the town of Paraiso do Sul.

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Source: Reuters