A newly discovered fossil may be that of the ancestor of modern day snakes, despite the fact that it possessed a very unsnake-like set of legs, paleontologists say.
The four legs of the new species, Tetrapodophis amplectus, weren't suitable for walking, so were most likely utilized to grasp and hold on to prey or to securely hold a partner during mating, the researchers say.
Living in the Early Cretaceous, 146 to 100 million years ago, the creature had classic snake features including a short snout, long, narrow braincase, and an elongated body with scales, plus fanged teeth and a flexible jaw to swallow large prey, they report in the journal Science.
While fossils of two-legged snakes have been found before, and modern-day pythons and boas still possess tiny vestigial spurs, this is the first known snake ancestor with a full set of four legs, says paleobiology professor David Martill of the University of Portsmouth in England.
"We've found the ancestor of all snakes," he says. "We have found the missing link between four-legged lizards and snakes."
Martill characterizes T. amplectus as a transitional animal between ancient lizards and modern snakes, saying, "This little animal is the Archaeopteryx of the squamate world." (Lizards and snakes taken together are known as squamates.)
The famously feathered Archeopteryx is considered the evolutionary half-way point between dinosaurs and birds.
Not everyone is ready to accept that T. amplectus is the ancestor of our modern snakes, and some experts say they even doubt if it's a snake at all.
"I honestly do not think so," says Michael Caldwell of the University of Alberta, who also studies ancient snakes, pointing to a lack of certain distinctive features in the fossil's spine and skull that would remove all doubt. "I think the specimen is important, but I do not know what it is."
Martill, for his part, maintains T. amplectus should be considered a candidate for both a true snake and a snake ancestor, although he acknowledges there are other possibilities.
"At any one time in the Cretaceous, chances are you've got 10, 20, maybe 30 species [of early snakes], all going off on their own evolutionary paths," he says. "There would be a whole bunch of very snake-like lizards, all with the potential to become today's snakes.
"One of them does."
