for National Geographic News
The elephant-size dinosaur Aerosteon riocoloradensis lived 85 million years ago during the Cretaceous period.
The fossil provides the first evidence of dinosaur air sacs, which pump air into the lungs and are used by modern-day birds, said Paul Sereno, the project's lead researcher and a National Geographic explorer-in-residence. (The National Geographic Society owns National Geographic News.)
Scientists have known dinosaurs used the pumplike apparatus to breathe, but the new find cements the connection between dinosaur and avian evolution, said Sereno, a paleontologist at the University of Chicago.
"This leaves little discussion that air sacs existed and that meat-eaters really do have lung structures that resemble birds," Sereno said.
(Related story: "Dinosaurs Had Supercharged Breathing Like Birds" [November 8, 2007])
Building a Case
Verifying that dinosaurs had bird-like breathing systems has been difficult because lungs do not fossilize, according to Sereno.
In Argentina, Sereno's team found the wishbone, hipbone, and stomach ribs of the newly found dinosaur species hollowed out—a telltale sign of air sacs.
Aerosteon had a sophisticated and extensive breathing system, said Brooks Britt, a paleontologist at Brigham Young University who studies birdlike dinosaurs and is familiar with Sereno's research.
Britt studies Allosaurus, the new dinosaur's closest relative, which lived 150 million years ago during the Jurassic period.
The two giants had something in common when it comes to birdlike features.
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