Dinosaurs Inside and Out
Do dinosaurs’ noses indicate they were not warm-blooded?
Some scientists believe that dinosaurs’ noses may tell us something about dinosaur metabolism. Respiratory turbinates are small scrolls of bone or cartilage in the nose covered with membranes; the absence of these bones in dinosaurs’ noses is probably a good indication that the animals were not warm-blooded. These turbinates are found in all warm-blooded animals, having evolved independently in mammals and birds; no known cold-blooded animals have them.
Warm-blooded animals breathe quite rapidly. The warm, exhaled air passes over the turbinates and cools, causing the moisture in the air to condense out onto the membranes. In turn, this prevents dehydration.
If dinosaurs were truly warm-blooded, they would need to have respiratory turbinates to prevent dehydration. Scientists recently used computer-aided tomography (CAT) scans to study dinosaur fossil skulls for any signs of respiratory turbinates. So far, the remains of Velociraptor and Nanotyrannus do not show any signs of these structures. Further analysis is planned to study fossil skulls from all the major groups of dinosaurs.