Modern lizards originated around 35 million years earlier than believed so far, according to a new study on a fossil in the Natural History Museum in London. Modern lizards were previously understood to have originated in the Middle Jurassic (174 to 163 million years ago) but the new study, published in Science Advances indicates that they existed as far back as the Late Triassic (237 to 201 million years ago).
The fossil is part of a museum collection stored since the 1950s. In those days, the technology didn’t exist to identify the exact species. The specimen was in a cupboard full of fossils of various reptiles from a quarry in Gloucestershire, England. The cupboard also contained many specimens of Clevosaurus, a common fossil reptile related to New Zealand’s Tuatara.
“Our specimen was simply labelled ‘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,” a release from the University of Bristol quoted lead researcher Dr David Whiteside as saying.
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The researchers made X-ray scans and reconstructed the fossil in three dimensions. They found the jaws of the reptile were filled with sharp-edged slicing teeth. They have named the new reptile Cryptovaranoides microlanius, meaning ‘small butcher’.
Several features indicate that Cryptovaranoides is clearly a squamate (a group comprising modern lizards and snakes). It differs from the Rhynchocephalia group (of which the New Zealand Tuatara is the only surviving member). These differences were 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 release said.
While Cryptovaranoides does have some features that are apparently primitive, such as a few rows of teeth on the bones of the roof of the mouth, these have also been observed in the living European Glass lizard and many snakes such as boas and pythons, which have multiple rows of large teeth in the same area.
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The new fossil impacts all estimates of the origin of Squamata.
“In terms of significance, our fossil shifts the origin and diversification of squamates back from the Middle Jurassic to the Late Triassic,” study co-author Professor Mike Benton was quoted as saying.