Paleontologists have denied the discovery of a fossil believed to be the missing link between lizards and the first snakes

(ORDO NEWS) — Filling the links of the evolutionary chain with the fossil remains of the “four-legged snake” connecting raptors and early snakes would be a dream come true for paleontologists.But a specimen previously thought to be suitable is not the missing piece of the puzzle , says a new study by the Journal of Systematic Palaeontology led by University of Alberta paleontologist Michael Caldwell.

“It has long been known that snakes are members of a genus of quadrupeds, which have lost limbs through evolutionary specialization,” said Caldwell, lead author of the study and professor in the Departments of Biological and Earth and Atmospheric Sciences.

“Somewhere in the fossil remains of ancient snakes, there is an ancestral form that still had four legs. Therefore, it was predicted long ago that a snake with four legs would be found as a fossil.”

Missing link found?

In a 2015 paper published in the journal Science, a team of researchers reported the discovery of what is believed to be the first known fossil of a four-legged snake – an animal they named Tetrapodophis amplectus.

“If interpreted correctly on the basis of the preserved anatomy, this will be a very important discovery,” Caldwell said.

Caldwell explained that a new study on Tetrapodophis has revealed a number of abnormalities in the specimen’s anatomy and morphology – traits that initially appeared to be most closely associated with snakes, suggesting that it may be a long-awaited snake with four legs.

” Finding a four-legged fossil snake can answer many evolutionary questions, but only if this is true . Our team’s main conclusion is that Tetrapodophis amplectus is not actually a snake and has been misclassified ,” Caldwell said. ” Rather, all aspects of its anatomy are consistent with the anatomy observed in a group of extinct Cretaceous sea lizards known as dolichosaurs .”

The key to this conclusion, Caldwell noted, lay in the rock from which the fossil was extracted.

“When the rock containing the specimen was cracked and found, the skeleton and skull were on opposite sides of the slab, with the natural cast retaining the shape of each on the opposite side,” Caldwell said. ” In the original study, only the skull was described and overlooked the natural shape, which retained several features, allowing it to be understood that the Tetrapodophis did not have a snake skull – not even a primitive one .”

Controversial instance

While Tetrapodophis may not be the four-legged snake so prized by paleontologists, it still has a lot to teach us, said study co-author Thiago Simoes, a former PhD student at the University of South Africa, a Harvard Graduate PhD student and a Brazilian paleontologist who pointed out some traits. making it unique.

“One of the biggest challenges in studying Tetrapodophis is that it is one of the smallest squat fossils ever found,” Simoes said. “It is comparable to the smallest living squat, which also has reduced limbs.”

An additional challenge for learning Tetrapodophis is access to the sample itself.

“ There were no appropriate export permits for the specimen from Brazil, and since publication it was kept in a private collection with limited access for researchers. This situation has generated a lot of resonance in the scientific community ,” says Simoens.

“In our new description of Tetrapodophis, we point to the important legal status of the specimen and emphasize the need for its repatriation to Brazil in accordance not only with Brazilian law, but also with international treaties and growing international efforts to reduce the influence of colonialist practice in science.”


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