- The Washington Times - Thursday, April 20, 2006

NEW YORK — A fossil find in Argentina has revealed a two-legged creature that’s the most primitive snake known, a discovery that promises to fire up the scientific debate about whether snakes evolved on land or in the sea.

The snake’s anatomy and the location of the fossil show that it lived on land, researchers said, adding evidence to the argument that snakes evolved on land.

Snakes are thought to have evolved from four-legged lizards, losing their legs over time. But scientists long have debated whether those ancestral lizards were land-based or marine creatures.

The newly found snake lived in Patagonia about 90 million years ago, scientists say. Its size is unknown, but it was not more than 3 feet long, said Hussam Zaher of the University of Sao Paulo in Brazil. He and an Argentine colleague reported the find in yesterday’s issue of the journal Nature.

It’s the first time that scientists have found a snake with a sacrum, a bony feature supporting the pelvis, Mr. Zaher said. That feature was lost as snakes evolved from lizards, he said, and since this is the only known snake that has not lost it, it must be the most primitive known.

The creature clearly lived on land, both because its anatomy suggests that it lived in burrows and because the deposits where the fossils were found came from a terrestrial environment, Mr. Zaher said. So, if the earliest-known snake lived on land, that suggests that snakes evolved on land, he said.

There has been little new evidence in recent years in the land-versus-sea debate, and “we needed something new,” Mr. Zaher said. “We needed a new start. And this snake is definitely a new start for this debate.”

He said that although the creature had two small rear legs, it crawled like a modern-day snake and probably used its legs only on occasion, though for what purpose is not clear.

The creature, named Najash rionegrina, is “a fantastic animal,” said Jack Conrad, a researcher at the American Museum of Natural History in New York.

Olivier Rieppel, a fossil reptile specialist at the Field Museum in Chicago, called the find important.

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