Sure, if you were an Ankylosaurus, you probably felt pretty good about yourself. Covered in armor, 30-feet long, weighing up to 13,000 pounds, you were an herbivorous tank. But on hot days, when you're exerting yourself and the temperature is rising, how do you cool off, big guy?
Sweating, panting, moving to the shade, or taking a dip in water are all time-honored methods used by animals to cool down. The implicit goal of these adaptations is always to keep the brain from overheating. But a group of researchers at Ohio University, led by paleontologist Jason Bourke — used CT scans to document the anatomy of nasal passages in two different ankylosaur species — and made an intriguing discovery:
Bourke discovered that these convoluted passageways would have allowed the inhaled air more time and more surface area to warm up to body temperature by drawing heat away from nearby blood vessels. As a result, the blood would be cooled, and pushed to the brain to keep its temperature stable.
Modern mammals and birds use scroll-shaped bones called conchae or turbinates to warm inhaled air. But ankylosaurs appear to have accomplished the same result with a completely different anatomical construction.
"There are two ways that animal noses transfer heat while breathing," says Bourke. "One is to pack a bunch of conchae into the air field, like most mammals and birds do – it's spatially efficient. The other option is to do what lizards and crocodiles do and simply take the nasal airway much longer. Ankylosaurs took the second approach to the extreme."
Lawrence Witmer, who was also involved in the study, said, "Our team discovered these 'crazy-straw' airways several years ago, but only recently have we been able to scientifically test hypotheses on how they functioned. By simulating airflow through these noses, we found that these stretched airways were effective heat exchangers. They would have allowed these multi-tonne beasts to keep their multi-ounce brains from overheating."
Like our own noses, ankylosaurs noses probably served more than one function. Even as it was conditioning the air it breathed, the convoluted passageways could have added resonance to the low-pitched sounds the animal uttered, allowing it to be heard over greater distances.