Elaine Hannah-11/04/16, Science World Report
The hailed first four-legged fossil snake is found to be not a snake, instead it is said to be an extinct four-legged marine lizard. In the new analysis, it indicates that it is a dolichosaurid with a stretched and snake-like body.
National Geographic reports that the 110-million-year fossil was unraveled as Tetrapodophis, a burrowing snake with two pairs of small limbs. This suggests that snakes started out on land. This caused issue and scientific debate about snakes losing their limbs on land or in water. In the current analysis, it suggests that the fossil could be the oldest known dolichosaur, which was an extinct marine lizard that existed during the Cretaceous period.
Michael Caldwell, a professor and chair of biological sciences at the University of Alberta in Edmonton in Canada explained that Tetrapodophis doesn't show any of those features that you would expect to see a snake. He further explained that it is likely a dolichosaurid, which belongs to the squamate (scaly reptile) umbrella. He added that it's unclear how dolichosaurids are associated with snakes. On the other hand, some evidence indicates that they are a sister group to the slithery reptiles, according to Live Science.
Caldwell continues that tetrapodophis amplectus does not have hooked teeth while a snake does. It also does not have a snake-like skull and skeleton. Some anatomical details that ancient and modern snakes have are also missing. These include the subdental ridge in the mouth and zygosphenes, which are special joints in between the snake vertebrae.
Meanwhile, the authors of the first study claimed that the Tetrapodophis is indeed a snake. David Martill, a paleontologist from the University of Portsmouth said that Caldwell is simply very wrong. He further said that they did consider a dolichosaur, yet it is not a dolichosaur. His co-author, Nick Longrich said that he stands behind the paper they wrote.
On the other hand, some paleontologists agreed on the findings of Caldwell. Jason Head, a paleontologist at the University of Cambridge said that he is sure that Caldwell is more right than the original publication. He further said that there was a lot of anatomical interpretation from the first study that he has a hard time seeing the photos.
Jacques Gauthier, a famous squamate expert from Yale said that he thinks that Caldwell makes a pretty good argument that it is a dolichosaur rather than a snake. On the other hand, he undermines Caldwell's ideas that snakes have aquatic origins.