Judging from the animals present at the site and their ages, as determined by radiometric dating of the surrounding volcanic rocks, the herd was probably made up of one- to seven-year-olds, said David Varricchio, a Montana State University paleontologist.
While the parents were devoting time to reproduction, the young took off on their own, said Varricchio, a co-author on the study published in December 2008 in the journal Acta Palaeontologica Polonica.
Sereno said via email: "We hope to learn more about the pace of growth and the number of nesting seasons per year from the skeletons."
The Gobi discovery "fits nicely with the emerging picture that dinosaurs were in many ways more like birds," said Hans-Dieter Sues, a paleontologist at the National Museum of Natural History in Washington, D.C.
(See related: "New 'Mini' Dinosaur a Step in Bird Evolution Path.")
"About everything we know about dinosaurs shows they're more like their descendants, birds," Sues added.
For instance, the group of young dinosaurs found at the Gobi site was not a coincidence, Sues said—such age groupings are seen in modern-day birds and was likely a behavior that evolved from dinosaurs.
Dinosaurs also demonstrated other complex, birdlike social behavior, such as brooding their eggs.
"There's a great element of serendipity" in the discovery of the Gobi mass grave, he said. "[Much] of what we know about social structures is based on such mass deaths."
SOURCES AND RELATED WEB SITES