Cryptovaranoides microlanius is an extinct relative of living lizards such as monitor lizards, gila monsters and slow worms.
An artist’s impression of Cryptovaranoides microlanius. Image credit: Lavinia Gandolfi.
Cryptovaranoides microlanius roamed our planet during the Late Triassic epoch.
This ancient species was identified from a fossilized specimen initially discovered in England in the 1950s.
“I first spotted the specimen in a cupboard full of Clevosaurus fossils in the storerooms of the Natural History Museum in London,” said Dr. David Whiteside, a researcher in the School of Earth Sciences at the University of Bristol.
“This was a common enough fossil reptile, a close relative of the New Zealand tuatara (Sphenodon punctatus) that is the only survivor of the group, the Rhynchocephalia, that split from the squamates over 240 million years ago.”
“Our specimen was simply labeled ‘Clevosaurus and one other reptile.’ As we continued to investigate the specimen, we became more and more convinced that it was actually more closely related to modern day lizards than the tuatara group.”
“We made X-ray scans of the fossils, and this enabled us to reconstruct the fossil in 3D, and to see all the tiny bones that were hidden inside the rock.”
The discovery of Cryptovaranoides microlanius reveals that modern lizards originated in the Late Triassic and not the Middle Jurassic as previously thought.
“Cryptovaranoides microlanius is clearly a squamate as it differs from the Rhynchocephalia in the braincase, in the neck vertebrae, in the shoulder region, in the presence of a median upper tooth in the front of the mouth, the way the teeth are set on a shelf in the jaws — rather than fused to the crest of the jaws — and in the skull architecture such as the lack of a lower temporal bar,” the paleontologists said.
“There is only one major primitive feature not found in modern squamates, an opening on one side of the end of the upper arm bone, the humerus, where an artery and nerve pass through.”
“Cryptovaranoides microlanius does have some other, apparently primitive characters such as a few rows of teeth on the bones of the roof of the mouth, but scientists have observed the same in the living European glass lizard and many snakes such as boas and pythons have multiple rows of large teeth in the same area.”
“Despite this, it is advanced like most living lizards in its braincase and the bone connections in the skull suggest that it was flexible.”
“In terms of significance, our fossil shifts the origin and diversification of squamates back from the Middle Jurassic to the Late Triassic,” added University of Bristol’s Professor Mike Benton.
“This was a time of major restructuring of ecosystems on land, with origins of new plant groups, especially modern-type conifers, as well as new kinds of insects, and some of the first of modern groups such as turtles, crocodilians, dinosaurs, and mammals.”
“Adding the oldest modern squamates then completes the picture. It seems these new plants and animals came on the scene as part of a major rebuilding of life on Earth after the end-Permian mass extinction 252 million years ago, and especially the Carnian Pluvial Episode, 232 million years ago when climates fluctuated between wet and dry and caused great perturbation to life.”
The team’s paper appears today in the journal Science Advances.
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D.I. Whiteside et al. 2022. A Triassic crown clade squamate. Science Advances 8: eabq8274
