Nov. 7, 2007 -- Meat-loving dinosaurs didn't huff and puff while chasing their prey, according to a new study that concludes dinosaur breathing was smooth and very similar to that of present-day diving birds.
The study, published today in the Proceedings of the Royal Society B: Biological Sciences, presents the first explanation for how carnivorous dinosaurs breathed. The researchers also believe large herbivorous dinosaurs, such as Diplodocus and Brachiosaurus, breathed like birds as well.
"Dinosaurs probably possessed a breathing mechanism that functioned like bellows," lead author Jonathan Codd told Discovery News. "It would have operated smoothly, allowing them to chase after prey at around 40 miles per hour without running out of breath."
Codd, a member of the Faculty of Life Sciences at the University of Manchester, and his team studied the fossilized remains of maniraptoran dinosaurs, such as Oviraptor philoceratops, Velociraptor mongoliensis and the tiny Microraptor zhaoianus. He and colleagues Phillip Manning, Mark Norell and Steven Perry also looked at fossils of extinct dino-era birds, including the most primitive known bird, Archaeopteryx, as well as bones from modern birds and crocodiles.
The scientists focused on tiny bones called "uncinate processes," which play an important role in modern bird breathing.
Birds breathe with their mouths closed, with air traveling through the nasal cavity before filling the lungs and multiple air sacs. Air can flow in and out due to moving bones, including the uncinate processes, which help to push the ribs outward, expanding the chest. If a bird couldn't move its ribs, it would suffocate.
Dinosaurs, like modern birds and crocodiles, were found to have the tiny, L-shaped uncinate processes that act as levers, moving the ribs and sternum out and in. Diving birds and dinos were found to have especially long levers, indicating very efficient breathing.
"At first, nobody even knew what role these structures played in modern birds," Codd said. "They're small and not particularly exciting to look at, so many people commonly misidentified them as rib bones poking out from the bird's back."
Since the dinosaur levers would have also pumped their abdomens full of air, dinosaurs also probably had the breath power of a trained singer who tries to fill his or her entire body, especially the abdomen, with air.
A big difference, however, is that dinosaurs would have had two exhalations for every inhalation, in contrast to our single "breathe in, breathe out" pattern, according to Codd.
"The function of uncinate processes, as proposed by Codd and collaborators, clearly could have facilitated the hypothesized...breathing mechanism of theropod dinosaurs," said David Carrier, a world-renown expert on bird and mammal breathing and locomotion.
Dinosaurs may have had respiratory systems similar to fowls, but did they have foul breath? Codd has his theories.
"It's quite likely," Codd said. "They possessed multiple teeth that would have trapped bits of rotting meat."
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