Dogs pant. Humans sweat. Pigs roll in the mud. To keep cool in the Cretaceous forests, some dinosaurs breathed deeply.
Paleontologists at Ohio University studied CT scans of the skulls of ankylosaurs - huge armor-plated dinosaurs.
Using 3-D reconstructions, they determined that traveling though the creatures' long, convoluted nasal passages gave air more time and surface area to warm up to body temperature by drawing heat from blood vessels.
The cooled blood then flowed to the brain to keep its temperature stable.
These "crazy-straw" airways, as the researchers called them, allowed the multiton animals to keep their multigram brains from overheating.
Writing in the Journal of Vertebrate Paleontology, the team adds that the size and shape of the tube may have given the ankylosaurs' low-pitched calls more resonance and carrying power.
Modern mammals and birds accomplish that heat transfer with coiled bones in their nasal passages. Reptiles have long nasal airways, but not nearly as long or as twisted as those of their ancient ancestors.