Young dinosaurs roamed together, die...( A herd of young birdlike dinosaurs m...)

A herd of young birdlike dinosaurs met their death on the muddy margins of a lake some 90 million years ago, according to a team of Chinese and American paleontologists that excavated the site in the Gobi Desert in western Inner Mongolia.

The Sudden sudden death of the herd in a mud trap provides a rare snapshot of social behavior. Composed entirely of juveniles of a single species of ornithomimid dinosaur (Sinornithomimus dongi), 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 Paul Sereno, professor at the University of Chicago and National Geographic Explorer-in-Residence. "These youngsters were roaming around on their own," remarked Tan Lin, from the Department of Land and Resources of Inner Mongolia.

Within an exquisite pair of the skeletons, prepared for display in Sereno's lab and airlifted back to China in late February, preserve stomach stones and the animal's' last meals are preserved.

Sereno, Tan and Zhao Xijin, professor in the Chinese Academy of Sciences, led the 2001 expedition that found the fossils. Team members also included David Varricchio of Montana State University (MSU), Jeffrey Wilson of the University of Michigan and Gabrielle Lyon of Project Exploration. The findings are published in the December 2008 issue of Acta Palaeontologica Polonica, and the work was funded by the National Geographic Society and the David and Lucile Packard Foundation.

"Finding a mired herd is exceedingly rare among living animals," said Varricchio, an assistant professor of paleontology at MSU. "The best examples are from hoofed mammals," such as water buffalo in Australia or feral horses in the American West, he said.

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 G
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