The search for the four-legged snake continues

Completing the links in the evolutionary chain with a fossil record of a “four-legged snake” connecting lizards and the first snakes is a wish for paleontologists.

But a specimen previously thought to fit the bill is not the missing piece of the puzzle, according to a new Journal of Systematic Palaeontology study led by paleontologist Michael Caldwell of the University of Alberta.

“It has long been understood that snakes are members of a lineage of four-legged vertebrates that, as a result of evolutionary specializations, lost their limbs”said Caldwell, lead author of the study and a professor in the earth and biological sciences and atmospheric sciences departments.

“Somewhere in the ancient snake fossil record is an ancient form that still had four legs. Therefore, it has long been predicted that a four-legged snake would be found as a fossil. “

In an article published in the journal Science in 2015, a team of researchers reported the discovery of what was believed to be an example of the first known four-legged snake fossil, an animal they called Tetrapodophis.

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

Caldwell explained that the new study of Tetrapodophis revealed a number of mischaracterizations of the specimen’s anatomy and morphology, traits that initially seemed to share more closely with snakes, suggesting that this could be the much sought-after four-legged snake.

“There are many evolutionary questions that could be answered by finding a four-legged snake fossil, but only if it is real. The main conclusion of our team is that Tetrapodophis amplectus is not in fact a snake and was misclassified “, expresó Caldwell.

“Rather, all aspects of their anatomy are consistent with the anatomy observed in a group of extinct marine lizards from the Cretaceous period known as dolicosaurs.”

Clues to this conclusion, Caldwell noted, were hidden in the rock from which the fossil was extracted.

“When the rock containing the specimen was split and discovered, the skeleton and skull ended up on opposite sides of the slab, with a natural mold that retained the shape of each on the opposite side”, dijo Caldwell.

“The original study only described the skull and ignored the natural mold, which retained several characteristics that make it clear that Tetrapodophis did not have the skull of a snake, not even a primitive one.”