A 205-million-year-old fossil rewrites the history of the modern lizard lineage

The significant find was considered to be a small, fossilized lizard hidden for decades in a museum cabinet.

This 205-million-year-old fossil, discovered in a quarry near Bristol, is the oldest modern-type lizard ever found.

This ancient lizard was a fearsome predator in its time. The original 2022 study named this fossil species Cryptovaranoides microlaniuswhich means “hidden lizard, little butcher”.

Scientists from the University of Bristol conducted a new analysis of the specimen and suggested it challenges our understanding of lizard evolution.

Interestingly, they claim that the fossil pushes back the origin of modern lizards by 35 million years.

Lizard fossil – skull in side view. David Whiteside

Discovered already in 1953

The fossil was discovered in a quarry in South Gloucestershire in 1953. In the 1980s, the fossilized specimen became part of the permanent collection of the Natural History Museum.

For years, its true identity remained unclear because scanning technology was not advanced enough to penetrate the rock surrounding the fossil.

A new study describes it as one of the oldest known lizards, pushing back the chronology of lizard evolution by millions of years.

The team proposes that the fossil is related to modern anguimorphs such as anguids and monitors.

Fossil studies suggest that lizard it was a carnivore equipped with sharp, blade-like teeth.

This tooth adaptation would have enabled it to successfully capture and eat insects, spiders and small vertebrates that were common during the Triassic period, over 200 million years ago.

A real debate about identity

By closely examining the fossil’s skull and skeleton, researchers were able to identify specific anatomical features that look similar to those found in modern lizards. It closely resembles the group Anguimorpha (which includes monitor lizards and worm lizards).

This detailed analysis allowed them to classify with confidence fossil as a member of the order Squamata, a group that includes all lizards and snakes.

It significantly predates the previously accepted origin of the Squamata clade by 35 million years.

“All details of the skull, jaws, teeth and limb bones confirm that Cryptovaranoides is a lizard and not an archosauromorph (related to crocodiles and dinosaurs),” said Professor Mike Benton, author of the study, who was also part of the original work.

The 2022 study sparked a debate about the classification of the fossil as a lizard. Some studies have even suggested that it has nothing to do with lizards.

The researchers performed a comprehensive phylogenetic analysis, comparing the fossil with different groups of lizards and archosaurs.

Using advanced imaging techniques, scientists managed to confirm the lizard’s identity beyond any doubt.

This analysis consistently confirmed their original conclusions, solidifying the fossil’s position as the oldest known modern-type lizard.

“We knew our publication would be controversial. But we were sure we checked every possible feature and compared it to everything we could,” said David Whiteside.

“In our new article, we detail every criticism expressed, and also provide more photos of the specimen and 3D images from the scans so anyone can check out the details,” Whiteside concluded in press release.

The results were published in the journal Royal Society Open Science.