Dinosaurs' noses may have air-conditioned their brains
The earth was a much hotter place in prehistoric times, so it follows that large heavily-armored dinosaurs likely retained a lot of heat in their bodies. A new study suggests that their brains were protected from overheating, however, thanks to a heat exchanging system in their noses.
Present-day birds and mammals (including humans) have curls of bone and cartilage within their nasal cavities, known as turbinates. These use body heat to warm inhaled air, by increasing the surface area that the air passes over on its way to the lungs. It turns out that the armor-plated ankylosaurus had an even more elaborate system, which it may have used to help cool its brain.
Led by Dr. Jason Bourke (from the New York Institute of Technology College of Osteopathic Medicine at Arkansas State University), a team of scientists started out by analyzing the fossilized skulls of two species of ankylosaur – the hippopotamus-sized Panoplosaurus and the rhinoceros-sized Euoplocephalus. More specifically, the researchers utilized computed tomography (CT) scanning and computational fluid dynamics to simulate how air moved through the animals' noses.
What they discovered was that while the dinosaurs lacked mammal-style turbinates, they had long coiled nasal passages that ran the length of their snouts. It is thought that when (relatively) cool outdoor air was inhaled and made its way down these passages, it absorbed a significant amount of heat from the hotter blood in the arteries surrounding them.
When that air was exhaled back out through those same passages, on the other hand, it wouldn't transfer much heat back into the blood, as the body-heated air and the blood were close to the same temperature. This resulted in a net loss of heat in the blood surrounding the passages – blood which veins subsequently carried to the brain. Additionally, evaporation of moisture in the passages likely boosted the cooling effect.
In order to test their theory, the scientists used a computer model to replace the dinosaurs' coiled passages with short, simple noses. It turned that in both species, this resulted in more than a 50 percent loss in heat transfer rates.
"The averaging between very cooled blood during an inhale, and only slightly cooled blood during an exhale would result in a net volume of consistently cooler blood heading towards the brain," Bourke explains to us. "This phenomenon is also observed in today's even-toed ungulates like deer and giraffes, which use a similar system to help control their brain temperatures."
A paper on the research was recently published in the journal PLOS ONE.
Source: New York Institute of Technology