An “absolutely exquisite” fossil of a snake that had four legs has been discovered by a team of scientists and may help show how snakes made the transition from lizards to serpents.
It is the first known fossil of a four-legged snake, and the team – led by Dr Dave Martill from the University of Portsmouth – say that this discovery could help scientists to understand how snakes lost their legs.
The findings are published in the journal Science.
Dr Martill said: “It is generally accepted that snakes evolved from lizards at some point in the distant past. What scientists don’t know yet is when they evolved, why they evolved, and what type of lizard they evolved from. This fossil answers some very important questions, for example it now seems clear to us that snakes evolved from burrowing lizards, not from marine lizards.”
The fossil, from Brazil, dates from the Cretaceous period and is 110 million years old, making it the oldest definitive snake.
“Discovery could help scientists to understand how snakes lost their legs”
Dr Martill discovered the fossil as part of a routine field trip with students to the prestigious Museum Solnhofen in Germany.
Dr Martill said: “The fossil was part of a larger exhibition of fossils from the Cretaceous period. It was clear that no-one had appreciated its importance, but when I saw it I knew it was an incredibly significant specimen.”
Dr Martill worked with expert German palaeontologist Helmut Tischlinger, who prepared and photographed the specimen, and Dr Nick Longrich from the University of Bath’s Milner Centre for Evolution, who studied the evolutionary relationships of the snake.
Dr Longrich, who had previously worked on snake origins, became intrigued when Martill told him the story over a pint at the local pub in Bath.
He said: “A four-legged snake seemed fantastic and as an evolutionary biologist, just too good to be true, it was especially interesting that it was put on display in a museum where anyone could see it.”
“A four-legged snake seemed fantastic and as an evolutionary biologist, just too good to be true”
He said he was initially sceptical, but when Dr Martill showed him Tischlinger’s photographs, he knew immediately that it was a fossil snake.
The snake, named Tetrapodophis amplectus by the team, is a juvenile and very small, measuring just 20cm from head to toe, although it may have grown much larger. The head is the size of an adult fingernail, and the smallest tail bone is only a quarter of a millimetre long. But the most remarkable thing about it is the presence of two sets of legs, or a pair of hands and a pair of feet.
The front legs are very small, about 1cm long, but have little elbows and wrists and hands that are just 5mm in length. The back legs are slightly longer and the feet are larger than the hands and could have been used to grasp its prey.
Dr Longrich said: “It is a perfect little snake, except it has these little arms and legs, and they have these strange long fingers and toes.