Washington, March 17 (ANI): A team of Chinese and American paleontologists has analyzed the skeletons of a herd of young birdlike dinosaurs that were found in a mud trap in the Gobi Desert in western Inner Mongolia, thus providing a rare snapshot of the social behavior of these dinos who roamed and died together 90 million years ago.
Paul Sereno, professor at the University of Chicago, Tan Lin, from the Department of Land and Resources of Inner Mongolia, and Zhao Xijin, professor in the Chinese Academy of Sciences, led the expedition that found the fossils in 2001.
"Finding a mired herd is exceedingly rare among living animals," said David Varricchio of Montana State University (MSU).
The first bones from the dinosaur herd were spotted by a Chinese geologist in 1978 at the base of a small hill in a desolate, windswept region of the Gobi Desert.
Some 20 years later, a Sino-Japanese team excavated the first skeletons, naming the dinosaur Sinornithomimus.
Sereno and associates then opened an expansive quarry, following one skeleton after another deep into the base of the hill. In sum, more than 25 individuals were excavated from the site.
They range in age from one to seven years, as determined by the annual growth rings in their bones.
The team meticulously recorded the position of all of the bones and the details of the rock layers to try to understand how so many animals of the same species perished in one place.
The skeletons showed similar exquisite preservation and were mostly facing the same direction, suggesting that they died together and over a short interval.
The details provided key evidence of an ancient tragedy. Two of the skeletons fell one right over the other.
Although most of their skeletons lay on a flat horizontal plane, their hind legs were stuck deeply in the mud below.
Only their hip bones were missing, which was likely the handiwork of a scavenger working over the meatiest part of the body bodies shortly after the animals died.
"These animals died a slow death in a mud trap, their flailing only serving to attract a nearby scavenger or predator," Sereno said.
Plunging marks in mud surrounding the skeletons recorded their failed attempts to escape.
The finding of the herd suggests that immature individuals were left to fend for themselves when adults were preoccupied with nesting or brooding.
"There were no adults or hatchlings," said Sereno. "These youngsters were roaming around on their own," remarked Tan Lin. (ANI)