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A fossil found in a cupboard at the Natural History Museum in London has moved the origins of lizards back millions of years.

The specimen has shown that modern lizards originated in the Late Triassic and not the Middle Jurassic as previously thought.

This fossilised relative of living lizards – such as monitor lizards, gila monsters and slow worms – was identified in a stored museum collection from the 1950s.

It included specimens from a quarry near Tortworth in Gloucestershire. The technology didn’t exist then to expose its contemporary features.

As a modern-type lizard, the new fossil impacts “all estimates” of the origin of lizards and snakes, together called the Squamata.

It affects assumptions about their rates of evolution, and even the key trigger for the origin of the group, scientists said.

The research team named their discovery Cryptovaranoides microlanius meaning “small butcher” in tribute to its jaws that were filled with sharp-edged teeth.

Dr David Whiteside, of Bristol University’s School of Earth Sciences, and leader of the study, said: “I first spotted the specimen in a cupboard full of Clevosaurus fossils in the storerooms of the Natural History Museum in London where I am a Scientific Associate.

“This was a common enough fossil reptile, a close relative of the New Zealand Tuatara that is the only survivor of the group, the Rhynchocephalia, that split from the squamates over 240 million years ago.

“Our specimen was simply labelled ‘Clevosaurus and one other reptile.’ As we continued to investigate the specimen, we became more and more convinced that it was actually more closely related to modern-day lizards than the Tuatara group.

“We made X-ray scans of the fossils at the University, and this enabled us to reconstruct the fossil in three dimensions, and to see all the tiny bones that were hidden inside the rock.”

He said that Cryptovaranoides is clearly a squamate as it differs from the Rhynchocephalia in the braincase, in the neck vertebrae, in the shoulder region and in the presence of a median upper tooth in the front of the mouth, the way the teeth are set on a shelf in the jaws.

Co-author Professor Mike Benton, said: “In terms of significance, our fossil shifts the origin and diversification of squamates back from the Middle Jurassic to the Late Triassic.

“This was a time of major restructuring of ecosystems on land, with origins of new plant groups, especially modern-type conifers, as well as new kinds of insects, and some of the first of modern groups such as turtles, crocodilians, dinosaurs, and mammals.

“Adding the oldest modern squamates then completes the picture. It seems these new plants and animals came on the scene as part of a major rebuilding of life on Earth after the end-Permian mass extinction 252 million years ago, and especially the Carnian Pluvial Episode, 232 million years ago when climates fluctuated between wet and dry and caused great perturbation to life.”

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