World’s Oldest Lizard Fossil Forces Reptile Family Tree Rethink | Evolution

The fossilized remains of a small lizard unearthed in rock in the Italian Alps have upended the evolutionary family tree of reptiles and shed new light on the survivors of the most devastating mass extinction the world has ever faced. according to the researchers.

Thought to have lived in the triassic periodabout 240 million years ago, the creature, known as the Megachirella wachtleriwas unveiled as the oldest known member of a group of reptiles called squamates – which includes lizards, snakes and peculiar legless creatures known as worm lizards.

The researchers say the discovery not only sheds light on what the last common ancestor of these creatures would likely have looked like, but reveals that the squamates likely appeared much earlier than previously thought and survived one of the biggest disasters on the planet.

“All lizards and snakes are descendants of Megachirelle or one Megachirelle-like a lizard,” said study co-author Dr Massimo Bernardi from the University of Bristol, adding that Megachirelle would probably have measured about 25-30 cm from its nose to the tip of its tail.

Write in the journal Naturean international team of researchers describe how they re-analyzed the 240m-old fossil of the creature which was first discovered in rock in the Dolomites in the early 2000s by an amateur collector.

Using an X-ray technique known as CT-scanning, the team was able to examine previously hidden features of the fossil in 3D. Additionally, they spent around 400 days visiting and examining some 150 specimens of ancient lizard-like creatures held in collections around the world, and analyzed skeletal and molecular data – including DNA – from squamates. living.

An artist’s impression of Megachirella wachtleri walking through the vegetation of the Dolomites 240 m years ago. Photography: Davide Bonadonna/Nature

The results reveal that Megachirella is a squamate, pushing the first known member of the group back by 75 million years and confirming some previous molecular studies that had proposed that squamates existed in the Triassic. Another result of the new family tree, according to the team, is that it settles a long-standing debate, revealing that geckos evolved earlier than iguanas.

And there’s more. By combining both molecular data and observations of skeletal features, the team was able to estimate when the first squamates appeared, revealing that they likely appeared just before the “Great Death” – an extinction event of catastrophic mass 252 million years ago when over 90% of marine creatures and 70% of terrestrial vertebrates died. This, Bernardi said, overturns current theories that they appeared after the disaster and reveals that many different species appeared in the aftermath of the disaster due to factors such as a lack of competitors. “It’s like the other side of extinctions,” he said. “Squamates, for example, were actually there before extinction, they went through [it] in a way, and they took the opportunities that came right after extinction,” he said.

Bernardi says Megachirella probably lived along the coasts, and the specimen found in the Dolomites met a watery end in the middle of a thunderstorm. “At that time, the geological reconstructions show us very clearly that the Dolomites were a series of islands with rich vegetation and fine sandy beaches, and probably Megachirella was walking along one of these beaches”, a- he declared. “[We think] it was taken by the storm because in the same [rock] layers, you see a lot of plants and debris and things that came from the land into the sea.

David Martill, a professor of paleobiology at the University of Portsmouth who was not involved in the study, said the revelation that the squamates appeared before the Great Death casts the creatures in a new light. “That means squamates are true survivors,” he said. “The Permo-Triassic extinction event was a dangerous time to live in. Little escaped its deadly touch.

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