Marine Half-Snake Discovered

An animal that may qualify as the remote ancestor of snakes has finally been brought to light after its fossil had languished unidentified for almost 100 years. This small lizard shows what could be the first step in the evolution of snakes and other legless lizards.

Named Adriosaurus microbrachis, its fossil remains were initially discovered in a limestone quarry in what is today the nation of Slovenia near the end of the 19th century. The rock containing the impression of its body was taken to the Natural History Museum in Trieste, Italy, and was pretty much forgotten until about ten years ago.

The find was just chronicled in the latest issue of the Journal of Vertebrate Paleontology. Adriosaurus was more snake than regular lizard, with a slim body and a tiny head at the end of a long neck. It measured about twelve inches in length, and while its rear legs appear normal for a lizard that size, it only had rudimentary stubs for front legs, a clear indication that this was a marine lizard. It lived about 95 million years ago.

Michael Caldwell, a member of the University of Alberta's paleontology team in Canada, and the person who rediscovered Adriosaurus in 1996 while he and a friend were visiting Europe and stopped at the Trieste museum, told reporters that this is the first fossil ever showing vestigal limbs in lizards. Caldwell and his team studied the fossil extensively before publishing their findings. Vestigal limbs are those lost through non-use during the evolutionary process. The front limbs were too small to be used for locomotion while Adriosaurus had seemingly functional rear legs. This shows that rear legs are more important than front ones when an animal has a slender body and a long neck, especially if it's an aquatic creature. The body and neck can be used as a whip to snap forward or to the sides to snatch food, making front legs unnecessary.

Most modern snakes have the vestigal remains of rear leg bones in their bodies, and this substantiates the idea that Adriosaurus was indeed some sort of transitional point between quadruped lizards and snakes. Scientists are a bit hesitant to say this is an actual "missing link", but they do agree it represents a terrific reference point for the loss of limbs in animals as they returned to aquatic life and eventually converted to slithering along the ground.