Fossil of a snake with legs helps reveal origin story of slithery reptile

21 Nov 2019

A render of Najash by Raúl O Gómez, Universidad de Buenos Aires. Image: Raúl O Gómez/ Universidad de Buenos Aires

Researchers have discovered the fossilised remains of an ancient snake that had legs, helping to paint a clearer evolutionary picture.

When it comes to understanding the mysterious evolution of snakes, the answer may lie in their skulls. An international team of researchers has published a study to Science Advances revealing new examples of an ancient legged snake.

The fossilised remains of the creature, called Najash, showed that snakes did have hind legs during the first 70m years of their evolution. Until recently, researchers have had a hard time tracking the evolution of the snake body due to limited fossil records of their earliest existence.

‘These primitive snakes with little legs weren’t just a transient evolutionary stage on the way to something better’

However, the discovery of this Najash showed what sets the snake apart from its lizard ancestors is its highly mobile skull, allowing it to swallow large prey. According to Flinders University’s Dr Alessandro Palci, one of the researchers on the team, this latest fossilised skull is so well preserved that it is providing an “amazing amount of new information” on how snakes’ heads evolved.

“It has some, but not all, of the flexible joints found in the skull of modern snakes,” he said. “Its middle ear is intermediate between that of lizards and living snakes and, unlike all living snakes, it retains a well-developed cheekbone, which again is reminiscent of that of lizards.”

When the Najash snake was first reported in Nature back in 2006, that specimen was revealed to be approximately 90m years old. What made its discovery unique was that it was a desert-dwelling snake as opposed to one that may have once lived in the ocean.

Palci’s colleague Prof Mike Lee, also part of the study, added that Najash proves Darwin’s predictions correct because it evolved from lizards in incremental evolutionary steps.

“These primitive snakes with little legs weren’t just a transient evolutionary stage on the way to something better,” Lee said.

“Rather, they had a highly successful body plan that persisted across many millions of years, and diversified into a range of terrestrial, burrowing and aquatic niches.”

Colm Gorey was a senior journalist with Silicon Republic