The dinos died together 90 million years ago after running into a sinkhole of mud in western Inner Mongolia, said Paul Sereno, a University of Chicago paleontologist who led the expedition.
The skeletons of the two-legged, plant-eating, Sinornithomimus dongi were so perfectly preserved they contained the remains of the dinos' last meal, Sereno told the Chicago Tribune in a story published Monday.
"In effect, it is like the first dinosaur Pompeii, a disaster that killed and preserved a society in midstride," said Sereno, whose team found the fossils in 2001. Sinornithomimus grew to 8 to 10 feet long and was covered in feathers, resembling modern ostriches, Sereno said.
Evidence suggests adult dinosaurs stayed at their nests with babies for extended periods of time, said Sereno, who concluded the mud-pit deaths were "like one of those unchaperoned high school parties where the adults leave the kids to shift for themselves."