They originated in the Late Triassic and not in the Middle Jurassic, as a fossil that has been in the Natural History Museum in London since the 1950s has shown.
A fossil that has been in the Natural History Museum in London since the 1950s has shown that modern lizards originated 35 million years ago, in the late Triassic and not in the middle Jurassic as previously thought.
The fossil had been found, along with others, in a quarry in Gloucestershire, southwest England, in the 1950s when the technology to expose its contemporary features did not exist.
The head of the team that has now proceeded to study its characteristics, David Whiteside, from the Bristol School of Earth Sciences (United Kingdom), remembers that the first time he saw it was in a cabinet full of Clevosaurus fossils.
“Our specimen was simply labeled ‘Clevosaurus and other reptile.’ As we investigated the specimen, we became more and more convinced that it was actually more closely related to living lizards than to the Tuatara group.”
The fossil is a relative of living lizards, such as monitor lizards or gila monsters.
Being a modern-type lizard, it affects all estimates of the origin of lizards and snakes, jointly called Squamata.
Baptized as ‘little butcher’, in homage to its jaws
In addition, it affects the assumptions about their rates of evolution, and even the key trigger for the origin of the group, have pointed out the authors of the study published in Science Advances.
“This is a very special fossil and it will probably become one of the most important found in recent decades,” Whiteside has indicated about the specimen, which has been named Cryptovaranoides microlanius (small butcher), in homage to its jaws, full of sharp teeth.
The team has carried out X-ray scans to reconstruct the fossil in three dimensions and see all the small bones that were hidden within the rock where it is found.
Cryptovaranoides is “clearly” a squamate, and there is only one important primitive feature not found in its modern relatives, an opening on one side of the end of the upper humeral bone, through which an artery and nerve pass.
“In terms of importance, our fossil shifts the origin and diversification of squamoses from the Middle Jurassic to the Late Triassic,” said Mike Benton, co-author of the study.
That was a time of great restructuring of terrestrial ecosystems after the mass extinction at the end of the Permian (252 million years ago).
At that time, new groups of plants arose, especially conifers of the modern type, as well as new types of insects and some of the first modern groups such as turtles, crocodiles, dinosaurs, and mammals.
Cryptovaranoides microlanius probably lived in limestone crevices on small islands that existed around Bristol at the time, feeding on arthropods and small vertebrates.