Rare Triassic fossil discovery may rewrite the history of dinosaurs

In a quiet and picturesque corner of southern Brazil known as Paraíso do Sul, an extraordinary treasure was uncovered — a fossil so ancient and well-preserved that it may potentially rewrite the narrative of dinosaur evolution.

This remarkable fossil belonged to a dog-sized reptile named Gondwanax paraisensis that roamed the region approximately 237 million years ago.

This was during the Triassic period — a time when Earth’s ecosystems were teeming with evolutionary experiments.

As a newly identified species, this fossil holds tremendous potential as a key to unraveling the mysteries surrounding the origin and early development of the oldest dinosaurs.

Although this fascinating discovery has sparked significant intrigue and excitement among paleontologists, the exact position of the fossil in the complex evolutionary tree of life still remains a subject of debate and careful scientific scrutiny.

Dinosaur history written in stone

In the realms of science, every fossil discovery is like a puzzle piece that can help us better understand our past. And when it comes to the world of paleontology, there are still many puzzles waiting to be solved.

Gondwanax paraisensis walked on four legs and was 39 inches in length, with a long tail. It belonged to an extinct group of reptiles known as silesaurids. These were not true dinosaurs, but are considered a closely related sister group to the dinosaurs.

However, this newly discovered fossil is one of the oldest silesaurids found anywhere in the world, and it may lead scientists to challenge currently accepted theories about the lineage and early evolution of dinosaurs.

“The most important part of this finding is its age,” said Rodrigo Temp Müller, the sole author of the study and a paleontologist at Federal University of Santa Maria in Brazil. “Because it’s so old, it gives us clues as to how dinosaurs came to be.”

Currently accepted dinosaur evolution theory

Scientists think dinosaurs first appeared about 230 million years ago during the Triassic period. They evolved from earlier reptiles and quickly diversified into a bunch of different species.

Over time, dinosaurs became the dominant land animals, filling all sorts of ecological roles. Some grew to massive sizes like the sauropods, while others became fierce predators like the Tyrannosaurus rex.

It’s wild to consider how they adapted and evolved unique features like horns, armor, and even feathers over millions of years.

One of the coolest things we’ve learned is that not all dinosaurs went extinct — birds are actually their modern descendants.

Birds evolved from small, feathered theropods, meaning every time you see a pigeon or a hawk, you’re looking at a living dinosaur.

This evolutionary link is supported by numerous fossil discoveries that show similarities in skeletal structures, feather patterns, and nesting behaviors.

Additionally, ongoing research continues to uncover how dinosaurs interacted with their environments and each other, shedding light on their complex social behaviors and survival strategies.

A lineage of questions

There is an ongoing debate among paleontologists about where silesaurids fit in terms of dinosaur evolution. Were they actual dinosaurs or were they just closely related ancestors?

The answer to this question is not straightforward. Some scientists believe that silesaurids are a sister group to dinosaurs, implying that they share a common ancestor but evolved separately.

Others, however, hypothesize that some silesaurids may have evolved into ornithischians — herbivorous dinosaurs, such as the Stegosaurus and Triceratops, that possessed a bird-like pelvic structure.

Understanding silesaurids could potentially lead to a better understanding of what physical traits contributed to the success of early dinosaurs.

However, solving this puzzle has not been an easy task as many fossils of silesaurids are found incomplete or fragmented, making it difficult for scientists to reach consensus regarding the position of silesaurids in the evolutionary tree of dinosaurs.

New clues about the history of dinosaurs

Physician Pedro Lucas Porcela Aurélio, who discovered the new fossil in 2014, was hit by an indescribable feeling. “Being the first human to touch something from 237 million years ago is extraordinary,” he remarked.

When Aurélio handed over the fossil to the paleontologists in 2021, it was encased in hard rock with only the vertebrae visible.

Surprisingly, Gondwanax was found to have three vertebrae in its hips, unlike its relatives who only had two. This difference suggested that this reptile may have been more dinosaur-like than previously assumed.

If this hypothesis is confirmed, it would not only extend the history of ornithischians (bird-like dinosaurs) by up to ten million years, but it would also significantly alter our understanding of dinosaur origin.

What happens next?

Despite the enthusiasm around the discovery, scientists still need more fossil evidence to confirm this theory.

Steve Brusatte, a paleontologist from the University of Edinburgh, highlighted this need for further exploration.

“I wish I could say that this new silesaurid fossil solves the riddle once and for all,” he said. “But for me, it is still an open question.”

We will be waiting eagerly for more pieces of this ancient puzzle to surface. Until then, the mystery of the dog-sized reptile continues to linger.

The study is published in the journal Gondwana Research.

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