Snakes (evolved) on a plain, scientists report

A new analysis of fossils suggests that snakes evolved their uniquely serpentine heads and bodies on land, not in the sea. The remains, collected in eastern Wyoming, are of a snake with a lizard-like head and a snake-like body.

The question of whether snakes evolved on land or in the sea has been hotly debated for years. Fueling the controversy is the fact that the fossil record is woefully incomplete, consisting mostly of vertebrae that give little indication of how important features -- in particular features of a snake’s head -- evolved. Most importantly, examples of so-called transitional species, animals that exist in evolutionary space between lizards and snakes, are few and far between.

The new study, published in Wednesday’s online edition of Nature, focuses on remains of the snake species Coniophis precedens, which lived roughly 70 million years ago during the late cretaceous period. While the snake had been described in the scientific literature and remains had previously been collected, those studies had only looked at vertebrae.

In the new report, researchers from Yale and Harvard analyzed the upper and lower jawbones of the snake as well as its vertebrae, and came to the conclusion that the snake was transitional because its head was more similar to a lizard’s than a snake. In particular, this snake lacks the ability to open its jaw wide and swallow prey whole, one of the hallmarks of modern snakes. The ancient snake likely ate small vertebrate animals.

Because the snake’s fossils are from the plains of Montana, the scientists argue that the remains provide strong evidence that modern snakes evolved on land. They suggest that the lizard-like head and long body indicate that early snakes evolved as burrowers.

Further, the scientists conclude that it wasn’t until the snakes evolved their flexible jaw and the ability to swallow larger prey whole that rapid diversification of snake species took place, leading to the nearly 3,000 species on Earth today.

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