Sebastian Apesteguia at the Argentine Museum of Natural History and his team found the snake fossil in a terrestrial deposit in the Rio Negro province of north Patagonia, Argentina, in 2003. Unlike a handful of legged fossils found in marine deposits and identified as snakes over the past decade, the new fossil, named Najash rionegrina, has a well-defined sacrum supporting a pelvis and functional hind legs outside of its ribcage.
The creature’s skeletal structure suggests it was evolutionarily closer to its four-legged ancestor than previous fossils. And since the scientists found it in a terrestrial deposit, it is near certain that the animal lived on land.
“This snake is an important addition because it is the first snake with a sacrum. This represents an intermediate morphology that has never before been seen,” says Hussam Zaher, curator of herpetology at the University of Sao Paulo in Brazil, and part of the research team.
The fossil was found in a deposit from the late Cretaceous period and Zaher says the snake is at least 90 million years old. “This fills an important morphological gap of information regarding the early evolution of snakes,” he says.
(via new scientist)
