MENDOZA, ArgentinaThe remains of a new 10-meter-long predatory dinosaur discovered along the banks of Argentina's Rio Colorado is helping to unravel how birds evolved their unusual breathing system.
Paleontologists led by the University of Chicago's Paul Sereno, a National Geographic Explorer-in-Residence, will publish their discovery Sept. 29 in the online journal Public Library of Science ONE. Joining Sereno to announce the discovery at a news conference in Mendoza, Argentina, today were Ricardo Martinez and Oscar Alcober, both of the Universidad Nacional de San Juan, Argentina.
The discovery of this dinosaur builds on decades of paleontological research indicating that birds evolved from dinosaurs.
"Among land animals, birds have a unique way of breathing. The lungs actually don't expand," Sereno said. Instead, birds have 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.
Discovered by Sereno and his colleagues in 1996, the new dinosaur is named Aerosteon riocoloradensis ("air bones from the Rio Colorado"). "Aerosteon, found in rocks dating to the Cretaceous period about 85 million years old, represents a lineage surviving in isolation in South America. Its closest cousin in North American, Allosaurus, had gone extinct millions of years earlier and was replaced by tyrannosaurs."
Laboratory technicians spent years cleaning and CT-scanning the bones, which were embedded in hard rock, to finally reveal the evidence of air sacs within Aerosteon's body cavity. Previously, paleontologists had found only tantalizing evidence in the backbone, outside the cavity with the lungs. "This dinosaur, unlike any other, provides more direct evidence of the bellows involved in bird breathing," Martinez said. Its bones have telltale pockets and a
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