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News Clippings

Discovery News 1999

Lizard-Snake Link Forged

Scientists have long puzzled over how snakes, with their slithery bodies and incredible jaws, evolved from lizards, but a new finding of a giant, extinct reptile appears to explain the evolutionary link.

Researchers have determined that mosasaurs, 45-foot marine lizards that lived about 100 million years ago, had flexible lower jaws like snakes and long, snake-like teeth to grip other critters. Findings are presented in the current issue of the journal Nature.

According to the report, jaw movement studies on a mosasaur fossil reveal that this huge Cretaceous reptile would get its dinner by biting onto large marine prey, such as sea turtles and other species of mosasaurs. Keeping a good tooth-hold, it would then manipulate its lower jaw and teeth to shove the creature down its esophagus.

Today, snakes eat using a similar process, only they also have a hinged, flexible upper jaw that allows them to wrap their entire skull around large prey.

Mosasaurs likely developed this dining technique because, as marine dwellers, they would have had a hard time dismembering prey in the water, says Gorden Bell, paleontologist with the Museum of Geology at the South Dakota School of Mines and Technology and one of the reportís authors.

"Competitors also would try to steal food right out of their mouths, so mosasaurs had to swallow it as soon as possible," he adds.

Bell and his colleagues think that mosasaurs were the nearest relatives of snakes, and that both reptiles shared a common ancestor, which is unknown at this point. Their theory goes against the popular belief that small burrowing lizards represented the intermediate stage of snake evolution.

In addition to the jaw and teeth similarities, the vertebrae of modern snakes resemble that of mosasaurs. Bell says the extinct giant reptiles slithered along in the water just as snakes do today on land.

Eric Pianka, professor of zoology at the University of Texas at Austin, thinks the report is "really interesting" and brings up an important subject, snake evolution.

"Here we are, almost at the year 2,000, and we still donít know exactly where snakes come from," says Pianka. "This report brings us a step further in attempting to reconstruct the snake family tree.

Pianka hopes researchers in the future will be able to analyze mosasaur DNA, possibly from a fossil tooth, to prove the snake connection theory.

By Jennifer Viegas, Discovery News Brief

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