European Light SourceCourtesy P. Ginter/ESRFThe second leg in the fossilized remains of a 92 million year-old snake has been revealed thanks to a powerful x-ray machine at the European Light Source (European Synchrotron Radiation Facility or ESRF) in Grenoble, France.

The fossil, frozen in a broken slab of Lebanese limestone, was discovered several years ago and described in 2000. One of the legs has always been visible on the surface of the fossil, but the other limb, trapped beneath the limestone matrix, was only suspected.

But using the powerful synchrotron device operating in a facility near the Alps, researchers bombarded the fossil with intense x-rays and were able to bring the second limb to light for the first time since its burial in the Late Cretaceous period.

The remarkable image shows a bent leg, complete with femur, tibia, and fibula. "We can even see ankle bones," said Paul Tafforeau, ESRF's resident paleontologist.

"In most cases, we can't find digits; but that may be because they are not preserved or because, as this is a vestigial leg, they were never present."

An image of the revealed second leg can be seen here at the BBC website. Scroll down to the middle of the page to see it.

The primitive snake, known as Eupodophis descouensi, is 33 inches long (although a 4 inch portion of it is missing). Its vestigial leg is only 0.8 inches.

Some modern snakes, such as pythons and boas, display hints of their evolved-away legs (called spurs), but evidence in the fossil record is extremely rare.

That’s why the ESRF is proving so useful. Through a process called computed laminography, it utilizes 2 dimensional pictures to construct a 3D image of hidden parts that scientists can study in detail without having to damage the rare and valuable fossil.

Snakes first appeared about 150 million years ago. The study of E. descouensi’s legs could help answer questions regarding snake origins either as evolving from sea lizards or from terrestrial ones that burrowed.

The high-energy light from the ESRF’s machine can peer through just about anything. Recently, it was reported to have revealed ancient insects trapped for 100 million years in opaque chunks of amber.

LINKS

BBC website story
ESRF website
More photos of ESRF
Natural History of Snakes