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Interviewee: Paul Sereno, University of Chicago
Dino Breathed Like a Bird
Discovering a new dinosaur is always exciting, but one particular meat-eating beast has given scientists a major new clue in the mystery of how birds evolved the ability to fly. The new dinosaur, named Aerosteon, seems to have had a unique breathing system that birds likely inherited through evolution.
As they wrote in the journal “PloS One,” Aerosteon’s bones are hollow. This is a major new link to birds.
In birds, hollow bones don’t just help them fly by making them lighter, they also help them breathe a lot more efficiently. The bones contain hollow chambers, or air sacs, that act as a kind of secondary lung system. As a bird breathes, half of the inhaled air is passed through the lungs and into one set of air sacs, while the other half passes directly into another set of sacs. When a bird exhales, air is passed from the sacs directly out of the trachea, without lingering in the lungs. The system functions so that air only passes in only one direction, preventing carbon dioxide-rich exhaled air from mixing with oxygen-rich inhaled air, as it does in mammal’s lungs.
Sereno says the fossil evidence indicates the same might have been true for Aerosteon, which roughly translates to “air bones.”
“What was really key was some of the bones around the rib cage of the animal, bones that only in birds are invaded by air sacs from the lungs,” says Sereno. “Having found these air pockets in Aerosteon, we reasoned that we really have to accept that Aerosteon and other predatory dinosaurs, likely feathered, these dinosaurs likely breathed like birds.”
While Aerosteon might have breathed like a bird, it certainly couldn’t fly. But it’s discovery is helping to put the theory that birds evolved from dinosaurs on more solid ground.
Sereno and his team found the 80-million-year-old giant in the badlands of Argentina, an area known as Patagonia.
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Eighty million years ago, in the Cretaceous period, the area would have been richly forested, with many flowing rivers and a vibrant ecosystem. Today, that same area is a hot, dry, almost desert-like environment. Not so great for a giant hungry dinosaur, but the perfect conditions for finding fossils.
Even in the right conditions, finding one particular fossil can be daunting. Paleontologists can spend weeks searching for a substantial find. As Sereno describes, “Any find, in hindsight, almost looks like an accident, because you go out into the area, it’s a vast area, and somehow you have to pull out a needle out of a haystack.”
One specific needle was particularly important: Aerosteon’s teeth. By examining the teeth of a dinosaur, a paleontologist can determine a lot about its lifestyle, eating habits, and what other species it is most closely related to. Judging from Aerosteon’s teeth, Sereno believes the theropod, or three-toed predatory dinosaur, could be a distant descendant of the fearsome Allosaurus. This fact is startling in and of itself, as the allosaurs were thought to have died out in South America long before the emergence of this new species. How did Aerosteon survive?
Sereno explains that, “Pangaea, the great supercontinent, which was the birthplace of dinosaurs, had broken apart, and South America was largely isolated onto its own. The Atlantic Ocean was narrower, but it was not connected to any other land masses.”
He believes the ancestors of Aerosteon were isolated to South America, surviving long after their relatives on the other continents died out due to competition from more advanced predators, like the tyrannosaurs.
And what would the Aerosteon have looked like? Sereno describes it as “an animal that’s about 30 feet long, would have been 2 legged, would probably have weighed about as much as an Indian Elephant.”
Although the dinosaur would have seemed impressively large to us, there are a number of predatory dinosaurs, like Tyrannosaurus Rex for example, which were significantly bigger. But what amazed Sereno wasn’t the creature’s size; for him it was all about the hollow bones.
So the next time you see a bird on the wing, remember that it’s flying, and breathing, courtesy of the dinosaurs.
PUBLICATIONS: Sereno PC, Martinez RN, Wilson JA, Varricchio DJ, Alcober OA, et al. 2008 Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina. PLoS ONE 3(9)
RESEARCH FUNDED BY: National Geographic Society
Elsewhere on the Web:
Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina – PloS ONE
Project Exploration – Nonprofit science education organization cofounded by Paul Sereno
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