研究：古蛇以恐龙幼仔为食

Sixty-seven million years ago, when dinosaur¹ hatchlings（刚孵化的幼体） first scrambled²（攀登，争夺） out of their eggs, their first—and last—glimpse of the world might have been the open jaws⁴ of a 3.5-metre-long snake named Sanajeh indicus, based on the discovery in India of a nearly complete fossilized skeleton（骨架，骨骼） of a primitive⁵（原始的，远古的） snake coiled（盘绕，卷） inside a dinosaur nest. The snake lacked the wide-jawed gape⁶（裂口，张嘴） seen in modern snakes such as pythons（蟒蛇） and boas, which would have prohibited it from eating rigid⁷ dinosaur eggs. But baby dinosaurs⁸ would have been just the right prey⁹ size for a large snake, says Jason Head, a paleontologist（古生物学者） and assistant professor in the Department of Biology at the University of Toronto Mississauga.

"Living primitive snakes are small animals whose diet is limited by their jaw³ size, but the evolution of a large body size in Sanajeh would have allowed it to eat a wide range of prey, including dinosaur hatchlings," says Head. "This is the first direct evidence of feeding behavior in a fossil primitive snake, and shows us that the ecology（生态学） and early evolutionary¹⁰ history of snakes were much more complex than we would think just by looking at modern snakes today."

The fossils were first found in 1987 by dinosaur egg expert Dhananjay Mohabey from the Geological Survey of India, in rocks of the Lameta Formation in Gujarat, a state in western India known for its rich fossil record of dinosaurs and their eggs. Originally identified as a hatchling dinosaur, the fossils were recognized to include a snake by dinosaur paleontologist Jeff Wilson from the University of Michigan and Mohabey in 2001.

"I saw the characteristic vertebrae（椎骨，脊椎） of a snake beside the dinosaur eggshell and larger bones, and I knew it was an extraordinary specimen¹¹ ... even if I couldn't put the whole story together at that point. I just knew we needed to examine it further," said Wilson. They invited snake specialist Head and geologist¹² Shanan Peters from the University of Wisconsin-Madison, to collaborate¹³ on the study of the fossils, including field and lab work in India, the U.S.A., and Canada.

Sanajeh indicus, which means "ancient gape from India", is represented by a nearly complete skull¹⁴ and lower jaws along with vertebrae and ribs¹⁵ coiled around a crushed titanosaur egg, next to the remains¹⁶ of a 0.5-metre-long titanosaur（雷龙） hatchling. These dinosaurs, part of a larger group called sauropods（蜥脚类动物） , were long-necked, four-legged plant-eaters that grew to weigh up to 100 tonnes, and Wilson says they likely grew quickly in their first year, beyond the reach of predators¹⁷（食肉动物，捕食者） like Sanajeh.

The findings—along with two other similar snake-egg pairings, suggest that snakes fed on titanosaur hatchlings when they emerged from their eggs. "The eggs were laid in loose sands and covered by a thin layer of sediment¹⁸（沉淀物，沉淀） . We think that the hatchling had just exited its egg, and its movement attracted the snake," explains Mohabey. "It would have been a smorgasbord（瑞典式自助餐） ," says Head. "Hundreds or thousands of defenseless baby sauropods could have supported an ecosystem¹⁹ of predators during the hatching season."

The remains capture a moment in Cretaceous time. "Burial was rapid and deep," says Peters. "Probably a pulse of slushy（泥泞的，融雪的） sand and mud released during a storm caught them in the act（当场，正要） ."