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Fossil found in drawer believed to be oldest known modern lizard | Fossils

Fossil found in drawer believed to be oldest known modern lizard | Fossils

The fossilized remains of a small, sharp-toothed lizard left in a cupboard for more than half a century pushed back the origin of the group that includes modern snakes and lizards by tens of millions of years.

The specimen was collected in the 1950s from a quarry near Tortworth in Gloucestershire by the late fossil hunter Pamela L. Robinson. But its true identity was not appreciated as the creature was mislabeled and kept in storage until recently when it was discovered at the Natural History Museum in London.

Now researchers say advances in technology have allowed them to take a second look, revealing that the creature occupies a central position in the reptilian family tree.

Artist’s impression of Cryptovaranoides when it was alive. Photo: Lavinia Gandolfi

“It’s partly a story of neglected fossils [a] drawer, and part story [that] without CT you wouldn’t have been able to do the work we’ve done,” said Prof Michael Benton, a palaeontologist at the University of Bristol and co-author of the study.

The long-tailed creature – about 25cm long – is believed to have lived around 202 million years ago. Cryptovaranoides microlanius. The first term means a hidden lizard-like animal, referring to its time spent unrecognized and its likely hiding in rock crevices during its lifetime. The second term, which translates as microbutcher, is a nod to the creature’s curved, blade-like teeth.

Using a CT scan, Benton and his colleagues were able to view the fossil in fine detail and study the bones trapped in the rock. Benson said the animal’s skull was 3 cm long. “The fossil is small, the ribs are quite small,” he said.

The results revealed that the animal was a scumate, one of the group of scaly reptiles that includes creatures such as lizards and snakes. “They started out as lizards — snakes evolved much later in the Cretaceous,” Benton said.

The creature has key distinguishing features of modern lizards, such as modified bones at the back of the skull to allow extra flexibility when opening the jaw, making it the oldest such reptile yet discovered.

Lizard head modeling.
Lizard head modeling. Photo: David Whiteside, Sophie Chamby-Trowell, Mike Benton and Natural History Museum UK

“It’s an angimorphic lizard that today includes 350 species, including everything from the gila monster in North America to the Komodo monitor, the huge predatory lizard in Indonesia,” Benton said.

The team says the find pushes the origin of modern scaly animals back at least 34 million years. The oldest known modern lizard is believed to have lived about 168 million years ago.

The team adds that the discovery has important implications for understanding the rate of evolution within the tree of life, as well as the time scale and causes of biodiversity in modern scaly animals – the latter of which may help conserve living species.

“Previously, the common ancestor of all these living forms was dated to the Middle Jurassic, whereas now we’re putting it back to the Late Triassic,” Benton said.

He said that while Cryptovaranoides microlanius was the closest living creature to the last common ancestor of modern scaly animals, its advanced features mean the title likely belongs to another, possibly even older, creature.

Professor Steve Brusat, a palaeontologist at the University of Edinburgh who was not involved in the work, said that while scientists had made a lot of progress in understanding theories about the origins of mammals, birds and crocodiles, the origins of lizards and snakes were more of a mystery.

Illustration of the skeleton showing the spine, lower jaw and limbs
Illustration of the skeleton showing the spine, lower jaw and limbs. Photo: David Whiteside, Sophie Chamby-Trowell, Mike Benton and Natural History Museum UK

“Few skeletons of these delicate animals are preserved as fossils, and many are so fragile that they prove very difficult to study,” he said.

“If its identification as a modern-style lizard is correct, it means that lizards began to diversify during the Triassic period, along with some of the earliest dinosaurs and mammals. It also proves that there are incredibly important British fossils still lurking, either in the field waiting to be discovered or in museum collections waiting to be properly studied.

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