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A Lizard Fossil, Found in a Storeroom Cupboard, Rewrites History

An ancestor to modern snakes and lizards was gathering dust in London's Natural History Museum.

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An illustration of the lizard based on the fossil found in a museum cupboard.
Lavinia Gandolfi

The entryway to the Natural History Museum in London houses one of the most impressive skeletons on Earth, suspended high above the ground. The 82-foot, 356-bone display is a monument to the planet's biggest creature, the blue whale. It's impossible to miss.

If you're working in the museum's storeroom, poring over specimens locked away in the cupboard for decades, it can be a lot harder to find something so impressive. But it isn't imposssible.

David Whiteside, a paleontologist at the University of Bristol, knows this better than most. While he was searching through a cupboard at the museum, he stumbled upon a skeleton that practically rewrites the history of modern lizards.

Whiteside found the specimen in a draw labeled "Clevosaurus," an ancient reptile that belonged to the group Rhynchocephalia. But there was one particular specimen that caught his eye. It was discovered in a Bristol quarry almost 70 years ago and contained a Clevosaurus fossil and another, unknown fossil. 

"We realized fairly quickly that it wasn't a Rhynchocephalian," Whiteside said. 

The tip off was the teeth, which were not the kind of teeth you'd find in the Rhynchocephalia.

Taking X-ray scans of the fossils allowed the team a chance to see all the tiny bones hidden inside the rock, according to Whiteside. 

An illustration of Cryptovaranoides microlanius as it may have appeared when it was alive.

Lavinia Gandolfi

The specimen contained a handful of bones, including the skull, jaw, spine and limbs. With high resolution scans, the team were able to show the unknown fossil was not another Clevosaurus but a specimen new to science. A separate braincase in the museum's collection "really made us sit up," Whiteside said, and suggested the fossil was of a squamate -- a group that includes today's lizards and snakes. 

It's not a big lizard, by any stretch. The length of the skull measures about 30mm, about half the size of an adult thumb. 

The team dubbed their find Cryptovaranoides microlanius. Its genus name takes the Greek "crypto" for "hidden" because it was found in a cupboard and because the team believes it likely lived in cracks between limestone rocks around ancient Bristol. The species name translates to "small butcher," in reference to its blade-like teeth. 

The team writes the discovery has "profound effects" on our understanding of squamate evolution. Previous finds suggested squamates originated and began to diversify sometime in the Middle Jurassic period, about 165 million years ago. Cryptovaranoides pushes that back to the Late Triassic, around 200 million years ago.

The success of the squamates and their ability to diversify may be the result of the Carnian pluvial episode, a period around 230 million years ago when the climate was changing and, according to fossil records, animals and plants were too. The team hypothesizes the expansion of the squamata might be linked to this event, but confirming this will depend on finding earlier fossils.

The team notes that further diversification happened during the Jurassic period and the Cretaceous, while the rhynchocephalians declined. There are over 11,000 species of squamates living today. However, there are some gaps in the fossil record for squamates, particularly during the Jurassic. Is that because of poor sampling or are they genuinely rare? It's hard to say, but I know where researchers might want to start their searches in the future.