The first known fossil of a four-legged snake has been discovered by scientists who believe it may help unravel the mystery of how serpents lost their legs.
Dr Dave Martill, from the University of Portsmouth, said the fossil, which he found in a collection in a German museum, showed that snakes evolved from burrowing lizards and not from marine lizards.
The fossil, from Brazil, dates from the Cretaceous period and is 110 million years old, which the scientists say makes it the oldest definitive snake.
“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.”
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.
The snake, named Tetrapodophis amplectus by the team, is a juvenile and very small, measuring just 20 cm 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.
The front legs are very small, about 1cm long, but have little elbows and wrists and hands that are just 5 mm 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.
“The hands and feet are very specialised for grasping. So when snakes stopped walking and started slithering, the legs didn’t just become useless little vestiges – they started using them for something else. We’re not entirely sure what that would be, but they may have been used for grasping prey, or perhaps mates.”
At the time, South America was united with Africa as part of a supercontinent known as Gondwana and the presence of the fossil suggests that snakes may originally have evolved on the ancient supercontinent, and only became widespread more recently.
