May 18, 2011
Fossil Sheds Light on the Lizard-Snake Divide
By SINDYA N. BHANOO
The origin of snakes is a perplexing matter. Although DNA analysis suggests that snakes are related to monitor lizards and iguanas, they are anatomically more similar to a group of earthwormlike creatures called worm lizards.
Now a new study helps clear the confusion, suggesting that worm lizards are related not to snakes, but to lacertids, a group of limbed lizards found in Europe, Africa and Asia.
Writing in the journal Nature, researchers identify a 47 million-year-old fossilized lizard in Germany that appears to be a common relative to both lacertids and worm lizards.
“This was the transitionary animal; it was exactly what we were looking for,” said Johannes Müller, a paleozoologist at the Natural History Museum in Berlin and the study’s first author. “It indirectly implies that identifying burrowing worm lizards with snakes is a mistake.”
Dr. Müller and his co-authors used X-ray computed tomography, or CT scans, to study the skull of the fossilized lizard and compare it with living lizards and snakes. They found that the fossilized lizard had a thickened, capsulelike skull with no external ear opening, similar to worm lizards.
The fossil was discovered in Messel Pit, a fossil site near Frankfurt and a Unesco World Heritage Site. The lizard, named Cryptolacerta hassiaca, is less than three inches in length and is the only known specimen of its kind.