A new dinosaur discovered in Argentina had labyrinthine lungs that extended into hollows in its ribs, hips, backbone, and wishbone. It's a rudimentary version of the lung system found in birds, where it allows breathing to be far more efficient than in mammals.
The dinosaur, named Aerosteon riocoloradensis this week in the open-access journal PLoS One, was a 30-foot long predator that raced about on two legs, though it lived some 17 million years earlier than Tyrannosaurus.
Disclaimer: Now, we at the Gist do realize that the Mesozoic world contained more than just rapacious bipedal predators. And we are looking forward to writing about, say, a peaceful, heavily armored, cycad-munching Ankylosaurus one of these days. We just can't help it that these newsworthy lung pockets happened to be found in the bones of a large, scary meateater.)
In fact, the new-fangled lungs and the body they came from might not be a coincidence at all. Air sacs nestled in the bones of birds help them route air through their lungs in a one-way circuit, so that nearly all the air is exchanged with each breath. By contrast, our own system of sucking air into the front of our lungs, then pushing it back out again, leaves lots of old, stale air in our lungs on any given breath.
For birds, their bellows-like breathing system is the equivalent of those blowers that stick out of the hoods of 1970s muscle cars: it's a ready supply of fresh oxygen they can use to supercharge their engines. That's one reason why birds can fly so explosively. And if Aerosteon's lung structure gave it the same sort of ability, it might make sense that the system evolved in an animal that has to run down prey for a living.
Of course, scientists are always wary of a good argument without good evidence - that's what they call an evolutionary Just-So Story. So lead author Paul Sereno and colleagues suggested a couple of alternative advantages that might have led to the appearance of Aerosteon's aerated bones (which, by the way, is what "aerosteon" means).
Shifting the lungs lower in the torso, they suggested, would lower the beast's center of gravity and place it over the legs, perhaps making it a better runner. Another possibility is that pushing more air across moist lung surfaces helped with evaporative cooling. Overheating can be a severe problem for large animals that live vigorous lives in warm climates, since heat has a harder time getting out of a large body than a small one.
Now, does anybody have any tips on late-breaking Ankylosaurus research?