The Serpent Speaks From Beyond the Grave

A new fossil discovery has revealed the most primitive snake known, a crawling creature with two legs, and it provides new evidence that snakes evolved on land rather than in the sea.

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

The new find reveals a snake that lived in the Patagonia region of Argentina some 90 million years ago, said Hussam Zaher of the University of Sao Paulo in Brazil, who describes the find in Thursday's issue of the journal Nature. Its size is unknown, but it wasn't more than 3 feet long, he said in a telephone interview.

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

The creature clearly lived on land, both because its anatomy suggests it lived in burrows and because the deposits in which the fossils were found came from a terrestrial environment, he said.

So, if the earliest known snake lived on land, that suggests snakes evolved on land, he said.

Little new evidence had appeared in recent years in the land-versus-sea debate, he said, and "we needed something new. We needed a new start. And this snake is definitely a new start for this debate."

While the creature still had two small rear legs, it crawled like a modern-day snake, he said. It probably used its legs only on occasion, though it's not clear for what, he said.

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