The findings, which appeared in Tuesday's issue of the PLoS Biology journal, provide the first evidence that the 11.5-foot-long snake fed on eggs and hatchlings of saurapod dinosaurs, meaning it was one of the few predators to prey on the long-necked herbivores.
They also suggest that, as early as 100 million years ago, snakes were developing mobile jaws similar to those of today's large-mouthed snakes, including vipers and boas.
"This is an early, well preserved snake, and it is doing something. We are capturing its behavior," said University of Michigan paleontologist Jeff Wilson, who is credited with recognizing the snake bones amid the crushed dinosaur eggs and bones of hatchlings.
"We have information about what this early snake did for living," he said. "It also helps us understand the early evolution of snakes both anatomically and ecologically."
Dhananjay Mohabey of India's Geological Survey discovered the fossilized remains in 1987, but he was only able to make out the dinosaur eggshells and limb bones. Wilson examined the fossils in 2001 and was "astonished" to find a predator in the midst of the sauropod's nest.
"I saw the characteristic vertebral locking mechanism of snakes alongside dinosaur eggshell and larger bones, and I knew it was an extraordinary specimen," Wilson said.
Mohabey theorized that the snake - dubbed Sanajeh indicus, which means "ancient gaped one" in Sanskrit - had just arrived at the nest and was in the process of gobbling a hatchling emerging from its egg. But the entire scene was "frozen in time" when it was hit by a storm or some other disaster and buried under layers of sediment.
"We think the hatchlings had just exited its egg, and the activity attracted the snake," Mohabey said, adding that the site in Western state of Gujarat has revealed about 30 sauropod nests and at least two other snake specimens.
Michael Benton of the University of Bristol, also writing in the PLoS Biology, said it can be difficult to determine the behavior of ancient organisms. But he said that it was "most likely, as the authors argue, that this snake was waiting and snatching juveniles as they hatched."
"Of course, we cannot be entirely sure unless further specimens come to light showing the bones of juvenile dinosaurs in the stomach region of the snake," Benton said.
Ashok Sahni, a senior scientist at the Indian National Science Academy who was also not involved in the dig, described the find as "truly remarkable" because it is rare for fossil bones to be preserved at the site of fossilized eggs.
"The scientific significance of the find is that it actually demonstrates behavior in early evolved snakes and the size of chosen prey," he said in an e-mail.
On the Web
PLoS Biology article: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000322