Famous discovery of four-legged snake fossil turns out to have a twist in the narrative

In 2015, paleontologists announced an amazing discovery. Preserved in chalk stone from Brazil was the complete skeleton of an animal resembling a snake, but with one significant addition: four small, almost rudimentary bones.

This marked something of a paleontological ‘holy grail’. The animal they named Tetrapodophis, was the missing joint between snakes and lizards.

There is only one problem. According to a new analysis of the remains, Tetrapodophis (from Greek meaning “four-legged snake”) is not at all a snake, but a species of extinct marine lizard that lived over 110 million years ago.

“There are many evolutionary questions that could be answered by finding a four-limbed snake fossil, but only if it is the right product,” says paleontologist Michael Caldwell of the University of Alberta in Canada.

“The most important conclusion from our team is this Tetrapodophis is not really a snake and was misclassified. On the contrary, all aspects of its anatomy are consistent with the anatomy observed in a group of extinct Cretaceous marine lizards known as dolichosaurs. “

It has long been accepted that snakes were not always the limbless wearers they are today. We even have other fossils that testify to this, such as Najash rionegrina, a snake from about 95 million years ago with two hind limbs, discovered in 2006.

The fossil record, paleontologists expected, should contain a four-legged snake somewhere in the dark corridors of the time.

Tetrapodophis looked like a very promising candidate. The 2015 study thoroughly examined and analyzed the creature’s bones, but very quickly Caldwell thought something was wrong. He and his colleagues presented a review in October 2016 at the Society of Vertebrate Paleontology meeting.

After examining the skeleton, they found that the teeth were not crooked or oriented like the teeth of a snake, and its skull and skeleton were not like those of a snake. The team also could not see the large ventral scales that would have helped mark it as a snake.

What’s more, in the stomach were the remnants of one of its last meals that appeared to be fish bones – consistent with an aquatic animal.

The new research goes even more in depth and picks up on something that the original study from 2015 completely missed: the stone in which the skeleton was encapsulated.

tetrapodophis plaster and skeletonThe skeleton of Tetrapodophis and the shape of its skeleton left in the rock. (Michael Caldwell)

“When the stone containing the sample was split and it was discovered, the skeleton and skull ended up on opposite sides of the plate, with a natural shape that retained the shape of each on the opposite side,” says Caldwell.

“The original study described only the skull and overlooked the natural mold, which retained several features that make it clear that Tetrapodophis did not have the skull like a serpent – not even a primitive one. “

The paleontologists behind the original claims about Tetraphodis’ snake membership stood by their observations in the wake of the criticism in 2016. Now that both studies are part of the literature, it will be up to future researchers to get down on both sides of the debate.

Although it is not a snake, it may now be incorrectly named Tetrapodophis still has a lot to teach us. The small skeleton is exquisitely preserved, which is an absolute gift for studies of dolichosaurs. But only if access can be gained. Currently, the test is in private hands, in violation of Brazilian law.

“There were no appropriate permits for the initial removal of the sample from Brazil, and since its initial publication, it has been housed in a private collection with limited access to researchers. The situation was met with a major setback from the scientific community,” the paleontologist said. Tiago Simões from Harvard University.

“In our description of Tetrapodophis“We define the important legal status of the specimen and emphasize the need for its repatriation to Brazil, in accordance with not only Brazilian law but also international treaties and the increasing international efforts to reduce the impact of colonialist practices in science.”

The team’s research has been published in Journal of Systematic Paleontology.

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