David Varricchio, in MSU's Department of Earth Sciences, said he and another paleontologist initially found pieces of vertebrae when he was working on a team led by Paul Sereno, now National Geographic Explorer in Residence at the University of Chicago. Further excavation by the team led to the unearthing of numerous vertebrae, ribs, pelvic elements and skull parts. Not until later did the researchers realize that several of the bones contained pockets, which indicated air sacs instead of marrow inside the bones.
It's not unusual to find such pockets in the vertebrae of meat-eating dinosaurs, but this dinosaur also had pockets in its wish bone, belly bones and the ilium, the major bone in the pelvis, Varricchio said.
"That provided the evidence that they had additional air sacs that would be present in birds," Varricchio said.
The discovery is described in an article published Sept. 30 in the online journal, Public Library of Science ONE. A press release from the University of Chicago said the discovery may have revealed how birds evolved their unusual breathing system.
"Among land animals, birds have a unique way of breathing. The lungs actually don't expand," Sereno said in the press release.
Instead, birds developed a system of bellows, or air sacs, which help pump air through the lungs. It's the reason birds can fly higher and faster than bats, which, like all mammals, expand their lungs in a less efficient breathing process, Sereno said.
The new dinosaur, called Aerosteon riocoloradodensis, was thought to be 85 million years old. Approximately 30-feet long, it was found along the banks of Argentina's Rio Colorado. Varricchio said he was working there in the fall of 1996 after earning his Ph.D. at MSU, about the same time he worked in Choteau.
Varricchio said the announcement of the "air bones" dinosaur came 12 years after the bones were discovered, in part, because the scientists were working on other projects and didn't realize immediately the significance of their find.
Evelyn Boswell, (406) 994-5135 or firstname.lastname@example.org