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 Picture of an ancient snake preparing to dine on dinosaur hatchling
A prehistoric snake threatens a dinosaur hatchling in a life-size reconstruction of fossils unearthed in India.

Image courtesy Ximena Erickson and Bonnie Miljour; sculpture by Tyler Keillor

Ker Than

for National Geographic News

Published March 1, 2010

Entombed at the moment of attack, a fossil serpent and sauropod are the first solid proof that prehistoric snakes ate dinosaurs, a new study says.

(See pictures of the dinosaur-eating snake.)

Found in India, the well-preserved dinosaur-nest scene boasts several fossils: a nearly complete snake, a newly emerged dinosaur, and two unhatched eggs—all apparently part of a spine-tingling tale.

One stormy day 67 million years ago, the 11.5-foot (3.5 meter) snake apparently slithered into the unguarded dinosaur nest. The snake had spotted a 1.6-foot-long (half-meter-long) dinosaur struggling out of its eggshell, scientists speculate.

The snake curled up next to the hatchling and was preparing to attack when heavy rains likely sent mud surging out of a nearby channel—smothering both snake and prey, according to the new study, to be published in this week's issue of the journal PLoS Biology.

(Related: "Venomous Dinosaur Discovered—Shocked Prey Like Snake?")

First Fossil Evidence of Snakes Eating Dinosaurs

The snake's interrupted meal offers a rare glimpse into the feeding behavior of ancient snakes and the dangers that newborn dinosaurs faced, said study team member Jeffrey Wilson, a University of Michigan paleontologist.

"It's actually one of the very few examples that we have of anything other than a dinosaur eating a dinosaur," said Wilson, whose work was funded in part by a grant from the National Geographic Society's Committee for Research and Exploration. (The National Geographic Society owns National Geographic News.)

Scientists have long known that some dinosaurs were egg snatchers, and recent fossil evidence suggests mammals also dined on young dinosaurs. (See "Five 'Oddball' Crocs Discovered, Including Dinosaur-Eater.")

It's been suspected that snakes too ate dinosaurs, but until now there had been no proof.

"It's a rough life if you're a juicy little dinosaur," Wilson said.

Dinosaur Devourer Was Lizard-like Snake

Modern large-mouthed snakes, such as boas and anacondas, can eat large prey because their jaw joints are positioned well behind their skulls, allowing the snakes to open their mouths very wide.

But the new species of prehistoric snake has a smaller mouth opening, like a lizard's. The snake's jaw joints were no farther aft than the back of the skull itself—earning it the name Sanejeh indicus, or "ancient-gaped one from India."

Even without giant jaws, though, Sanejeh "could swallow big things"—such as baby dinosaurs— simply because the snake itself was big, Wilson said.

"If the snake had evolved the machinery that modern snakes have, it would have been able to take even bigger things," he said.

Sanejeh did have a key adaptation also found in modern snakes: an upper jaw that can move independently of the lower jaw.

This jaw structure would have allowed Sanejeh to wriggle, mouth first, over struggling prey in an alternating side-to-side motion familiar to anyone who has ever tried to squeeze into a tight pair of jeans. (See a picture of a python that's eaten a pregnant sheep.)

The snake may also have been capable of squeezing dinosaur eggs open to get to the hatchlings inside.

But because modern snakes tend not to attack inanimate objects, the researchers believe ancient snakes behaved similarly, so it's likely that the young dinosaur had already hatched before the snake arrived.

Young Dinosaurs Outgrew Snake Predators?

Due to the apparent victim's young age, the team couldn't determine the dinosaur's species. But they do know it was a sauropod—a giant long-necked plant-eater (sauropod picture). But what kind?

Previously discovered fossils suggest that titanosaurs—sauropods that grew to lengths of 65 feet (20 meters) or longer—roamed the region around the nest, leading the researchers to suggest the hatchling too was a titanosaur. (See "Eggs Hold Skulls of Titanosaur Embryos.")

The fossils of Sanejeh and its apparent prey were discovered in western India's Gujarat Province in 1984. After being mislabeled as containing only a hatchling sauropod, the fossil trove was separated before finally being reunited in 2004 and sent to the University of Michigan for study.

To avoid being eaten by snakes and other predators, sauropods, in general, probably underwent growth spurts in their early years, the study says. (Related: "Dinosaur-Size Spurt: T. Rex Teens Gained Five Pounds a Day.")

"By the time this sauropod was about a year old, we think it would have been out of the range of Sanejeh," Wilson said.

Dinosaur-Eating Snakes Not Surprising?

"The discovery is very interesting, and I think the study's conclusions are reasonable about the snake possibly feeding on hatchling dinosaurs," said Brad Moon, a herpetologist at the University of Louisiana at Lafayette, who was not involved in the new research.

Moon does think, though, that Sanejeh may have been attracted to the dinosaur nest for other reasons. For example, the snake might have simply been seeking shelter or pursuing some other animal, he said.

And while certainly spectacular, the revelation of a snake attack in progress is less than surprising, scientifically speaking, according to George Zug, curator emeritus of amphibians and reptiles at the National Museum of Natural History in Washington, D.C.

Though Zug agrees the new fossils are the first proof of snakes eating dinosaurs, he said the behavior wouldn't shock anyone familiar with the ways of modern snakes.

Snakes eat not only mammals and birds but also other reptiles, such as frogs and even other snakes, said Zug, who was not involved in the new study.

"So it's not out of the question that they would be preying on little dinosaurs."

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