"The pulmonary system of meat-eating dinosaurs such as T. rex in fact shares many structural similarities with that of modern birds, which, from an engineering point of view, may possess the most efficient respiratory system of any living vertebrate inhabiting the land or sky," said Claessens, who received a Ph.D. from Harvard in organismic and evolutionary biology last month and will join the faculty at the College of the Holy Cross in Worcester, Mass., this fall.
In birds, this special anatomical configuration increases the gas exchange potential within the lungs, boosting metabolism and creating warm-bloodedness. The researchers are quick to point out, however, that the new study doesn't clearly peg predatory dinosaurs as habitually warm-blooded animals. The creatures probably had a more complex strategy, falling somewhere between what scientists define as cold- and warm-blooded. It appears that these animals had the pulmonary machinery for enhanced gas exchange, O'Connor explained, which would have pushed them closer to being warm-blooded creatures.
Previous research that pointed to a more crocodilian-like pulmonary system was based on a study of two dinosaur skeletons encased in rock. O'Connor and Claessens have expanded on that research by studying a broader collection of dinosaur skeletal remains, and are the first to integrate both anatomical and functional studies of modern birds as models of how the ancient creatures' air sacs were structured.
The scientists are part of a reinvigorated movement of researchers who are examining dinosaur bones and comparing them with modern animals to learn more about the anatomy of th