Dinosaurs’ mishap a boon for paleontologists

CHICAGO – Horsing around without adult supervision, a large group of adolescent and pre-adolescent dinosaurs died en masse 90 million years ago when they ran pell mell into a mudhole, sinking to their doom.

Terrible as the consequences were, the dinosaurs’ remains are providing a bonanza of new knowledge for a group of Chinese and American paleontologists who excavated the fossils in the Gobi Desert in western Inner Mongolia.

Many of the 25 individuals recovered were complete skeletons, so perfectly preserved the remains of their last meals were found, too. Because they are all from the same species, a two-legged plant-eater called Sinornithomimus dongi, or “Chinese bird mimic,” the fossils yield rare insight into the social behavior of the animal.

“That is something really tough to do, extracting behavioral information about animals from their fossil bones,” said University of Chicago paleontologist Paul Sereno, who led the expedition.

“In effect, it is like the first dinosaur Pompeii, a disaster that killed and preserved a society in midstride,” he said. “It gives us information on how these animals acted, how they were organized socially.”

The most intriguing new concept in the report is the idea that the dinosaurs were a group of juveniles and sub-adults living together, with no babies and no adults, said Tom Holtz, a University of Maryland paleontologist not connected to Sereno’s China expedition.

“We already have evidence that adult dinosaurs stayed with babies at their nests for extended periods of time,” Holtz said. “Nobody has considered what the older kids were doing while their parents concentrated on the hatchlings in the nest. The answer seems to be … the teenagers ran together on their own with the pre-teens following along. It was sort of like the population of a shopping mall.”

The report is published in the online science journal Acta Palaeontologica Polonica.