for National Geographic News
"Fowl" breath may have been the secret weapon of the fleet-footed predators of Jurassic Park fame.
A new study says that velociraptors and some other theropods—two-legged meat-eating dinosaurs closely related to birds—breathed like today's geese and penguins.
Like most birds, these dinosaurs had, in addition to lungs, air sacs attached to their spines, the fossil study found. This ultra-efficient breathing system would have helped make the dinosaurs speedy predators.
The finding is based on the identification of small bones like those that, in birds, act as levers, moving the ribs up and down, aerating the air sacs.
"We think that the dinosaurs would have had an effective respiratory system, as we know that the bird system is highly efficient and has a lot of adaptations that enable the birds to fly, which is very energetically expensive," said study leader Jonathan Codd, a biologist from the University of Manchester in the United Kingdom.
The study appears this week in the journal Proceedings of the Royal Society B: Biological Sciences.
Codd and his colleagues examined fossils of dinosaurs and extinct birds, such as Archaeopteryx, in museum collections around the world. The researchers found that some dinosaurs had these tiny, rib-moving bones, called uncinate processes.
"We mammals have a diaphragm, which allows the lungs to change volume when we breathe," said study co-author Phil Manning, a paleontologist from the university. (Some of Manning's work is funded by the Expeditions Council of the National Geographic Society, which owns National Geographic News.)
Birds—descendents of dinosaurs—don't have diaphragms. Instead, birds use their sternum, combined with muscles attached to the uncinates, as a respiratory "pump" to power their energetic activities.
"Our work suggests that the uncinate processes—present in almost all living species of bird and also in the fossil remains of [some] theropod dinosaurs—was a key adaptation in dinosaurs, specifically assisting in the 'squeeze-box' process of changing the chest volume to assist breathing."
According to the researchers, so-called maniraptoran dinosaurs, which include velociraptors, studied from the fossil record had long uncinate processes similar in structure to those of modern-day diving birds.
"Although many researchers have long posited some type of an air sac based pulmonary system in theropod dinosaurs, this new study explicitly addresses the possible function of uncinate processes and how these structures may have played a role in pulmonary function," said Patrick O'Connor, assistant professor of anatomy at Ohio University. O'Connor was not involved in the study.
The findings support the theory that the efficient respiratory system of these running dinosaurs made them speedy beasts when pursuing their prey.
The University of Manchester's Manning said, "The maniraptoran dinosaurs were a pretty effective group of predators. These were nasty, toothy, powerful, and fleet-of-foot predators."
"If they were around today, I somewhat doubt that we would have made it up the evolutionary ladder to see them."
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