Chico blog

X-rays Reveal Ancient Snake's Hidden Leg

A new look at a 95-million-year-old fossilized snake revealstwo tiny leg bones attached to the slithery creature's pelvis. Athree-dimensional reconstruction of the bones could help researchers understandhow snakes evolved to lose their legs.

The fossil, found in Lebanon, is from an era when snakes hadnot yet completely lost the hind limbs leftby their lizard ancestors. A much-debated question among paleontologists iswhether these leggy ancestors were ocean-living swimmers or land-dwellingburrowing lizards.

The new finding takes a stab at answering that question.

One-inch-long fossilized leg bone is visible on the surfaceof the fossilized Lebanese snake, but half the pelvis (where another leg wouldbe expected) is buried in rock. The 19-inch-long (50 centimeter) snake (called Eupodophis descouensi) is one of onlythree snake fossils with its hind limbs preserved, so breaking it open to lookfor the other leg was out of the question, said study researcher AlexandraHoussaye of the Museum National d'Histoire Naturelle in Paris.

Instead, the researchers used a technique calledsynchrotron-radiation computed laminography (SRCL). Like a medical computedtomography (CT) scan, SRCL uses X-rays to image the internal structure of anobject, but at 1,000 times higher resolution.

"Only 3-D [scanning] could reveal the inner structureof the bones without damaging them, and the same is true to observe thecomplete second leg," Houssaye told LiveScience.

The scanning revealed a hidden leg, bent at the knee butlacking foot and toe bones. The setup of the bones is similar to that ofterrestrial lizards, Houssaye said, adding that one study couldn't settle the "landancestor versus water ancestor" debate. However, she said, the anatomy ofthe bones suggests that evolution tooksnakes' legs not by altering the way they grew. Instead, Houssaye said, itlooks as though the limbs grew either slower or for a shorter period of time.

This experiment was the first to use the SRCL technique inpaleontology, Houssaye said, and there's much more to analyze. The next steps,she said, include analyzing other hind-limb snakefossils, studying the limbs of living snakes and lizards and analyzing thefossils of the oldest snakes known.

The researchers report their results in the Feb. 8 issue ofthe Journal of Vertebrate Paleontology.

Top 10Useless Limbs (and Other Vestigial Organs)Millions ofYears Ago, Snakes Were Hip7Shocking Snake Stories

You can follow LiveScience Senior Writer Stephanie Pappas on Twitter @sipappas.

Original Story: