Fossil found in drawer is oldest known modern lizard

The fossilized remains of a small, sharp-toothed lizard, left in a closet for more than half a century, pushed back the origins of the group that encompasses 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 has not been appreciated as the creature was mistakenly labeled and stored, until recently when it was found 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 reptile family tree.

“It’s partly a story of neglected fossils in [a] drawer, and partially a story [that] without the scanner you wouldn’t have been able to do the work that we did,” said Professor Michael Benton, a paleontologist at the University of Bristol and co-author of the research.

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

Using CT scans, Benton and his colleagues were able to observe the fossil in great detail and study the bones trapped in the rock. Benson said the animal’s skull was 3cm long. “The fossil is tiny, the ribs are just tiny,” he said.

The results reveal the animal was a squamate – one of a group of scaled reptiles that includes creatures such as lizards and snakes. “They started out as lizards – snakes evolve a bit later in the Cretaceous,” Benton said.

The creature has key features of modern lizards, such as modified bones in the back of the skull to allow extra flexibility in jaw opening, making it the oldest reptile found to date.

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

The team says the discovery pushes the origins of modern squamates back by at least 34 million years. The oldest known modern lizard was thought to have lived around 168 million years ago.

The team adds that the discovery has important implications for understanding the rate of evolution in the tree of life, as well as the time scale and triggers of biodiversity in modern squamates – the latter of which may aid in the conservation of living species.

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

He said that during Cryptovaranoides microlanius was the closest scientist to the last common ancestor of modern squamates, its advanced features mean the title likely belongs to another, perhaps even older, creature.

Professor Steve Brusatte, a paleontologist at the University of Edinburgh who was not involved in the work, said that while scientists had made many advances in understanding the origins of mammals, birds and crocodiles, the ancestry lizards and snakes was more of a mystery.

“There are few skeletons of these delicate animals that have been preserved as fossils, and many of them are so fragile that they have proven very difficult to study,” he said.

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