Snake Supper

A key part of the investigation came when Wilson and Mohabey uncovered a long-lost piece of the original fossil that provided evidence of the snake's relationship to the dinosaur. "When we found the last piece of fossil matrix and snapped it into place, we could clearly see the snake was coiled around a dinosaur egg — it was incredible," recalls Wilson.

Though Sanajeh was large, the snake's skull structure suggests that it could not open its jaws very far. A wide gape is crucial to large snakes like modern boas and pythons, which crush and eat animals by wrapping their mouths around their prey and swallowing them whole. That Sanajeh could not do this suggests that it was unable to eat the large and hard-shelled eggs that it was coiled around, but instead waited in the nest to eat smaller and softer hatchling dinosaurs.

Palaeontologist Angela Milner at the Natural History Museum in London, who was not involved in the research, says the study is the first to report a snake in association with a dinosaur nesting site. Many dinosaurs nested communally to gain safety in numbers. That would be attractive to a range of nest predators such as snakes, says Milner. "Newly emerged hatchlings would have been sitting ducks before they had time to disperse...so it seems Sanajeh hung around the eggs waiting for an easy meal," she says.

Wilson's team say other nests at the same site in India also show the presence of bones of the same snake, suggesting that they regularly preyed on dinosaurs in this way. "This points to a predation pressure on sauropods that we had not really considered before," says Wilson. The dinosaur hatchlings likely grew fast to get themselves too large to be eaten by Sanajeh, he explains.

Like most of the land-based reptiles on the Indian subcontinent that Wilson and his colleagues have studied, the Sanajeh bones show puzzling links to fauna on southern landmasses, such as Africa, Antarctica, Australia and Madagascar.

India was interlocked with these areas in its remote past, but plate reconstructions show the continent became geographically isolated for a long stretch of its northward drift before it connected with Asia 50 million years ago. Despite this isolation, "India's biota retained a strong southern connection — but how that was accomplished remains a mystery", Wilson adds.