​Dinosaurs’ Noses Kept Their Brains from Melting, Study Finds

It’s like having an air conditioner on your face.

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Oct 25 2015, 2:18pm

Pachycephalosaurus model. Image: Angela Marie Henriette/Flickr/Flickr

It's crazy to think that with each breath, you might be inhaling atoms that were at one point part of a dinosaur. But before you go get all excited about how much you have in common with your dino buds, it's probably worth telling you that while you two may have breathed the same air, the dinosaurs were breathing it a lot differently—and that may have been critical to their survival.

Using principles of computational fluid dynamics, researchers from Ohio University modeled the flow of air and heat through the nasal passages of various dinosaurs, demonstrating that the perplexing size and complexity of dino noses is probably the reason these behemoths didn't end up cooking their own brains.

The complexity and size of dinosaur nasal passages has long perplexed researchers who concern themselves with dinosaur physiology, wrote Jason Bourke, a graduate student at OU and lead author of a study published last October in The Anatomical Record. Bourke expanded on these findings last week at the Annual Meeting of the Society of Vertebrate Paleontology in Dallas, Texas.

One of the primary problems in cracking the mystery of dinosaurs' noses was that all the flesh that comprised the cavity rotted away millions of years ago, leaving researchers with few hints as to how they might have been constructed.

Animation of this airflow process in a Stegoceras

Thanks to funding from the National Science Foundation's Visible Interactive Dinosaur Project, Bourke and his colleagues were able to the modern day relatives of dinosaurs—birds, crocodiles, and lizards—to look for clues as to how to begin reconstructing dinosaurs' noses. After they had gathered enough data through dissections and CT scans, the team went virtual, running airflow simulations to see how these animals breathe.

After that, it was all about finding a suitable dinosaur candidate on which to test their models. They ultimately chose the pachycephalosaurs, a group of herbivores which are distinguished by a bone on the top of their heads several inches thick. While paleontologists are pretty certain this bone structure was used both as a visual display and as protection, it came with a curious secondary effect: it turned soft tissues in other parts of the body to bone, most notably the nose, in a process common to all vertebrates known as ossification.

"The difference in pachycephalosaurs was that this normal process of bone formation seems to have been turned up to eleven," Bourke told me. "This produced the thick domes on their heads, but it also seems to have caused calcium to deposit on other soft-tissue structures, such as the cartilage inside the nose or on the brow ridge. This process is called hypermineralizaton, and pachycephalosaurs seem to have had it in spades."

Interestingly, when the team looked at the skulls of SphaerotholusandStegoceras (two genera of pachycephalosaurid), they noticed small "scrolls of bone in the nasal region" called turbinates. The presence of these turbinates had previously been linked to smell, yet Bourke's modeling shows that for these dinosaurs they had an additional function: helping to keep their brains cool.

The team's research revealed that in dinosaurs, blood likely passed over these turbinates on its way to the brain, the airflow cooling the blood during its journey. In this respect, the pachycephalosaurs turns out to be remarkably similar to modern day ostriches and crocodiles.

At the Society of Vertebrate Paleontology conference last week, Bourke expanded on this research by looking at other dinosaurs, such as theropods (like T. rex) and the armored Ankylosaurus, to test a 16-year-old theory advanced by Larry Witmer and Scott Sampson, who hypothesized that the reason larger dinosaurs had larger noses than smaller dinosaurs was so the nose would act as a heat sink, dumping excess heat from the deep core of their bodies, much like elephants do with their ears.

What he found was that the Ankylosaurus, which has a nasal passage like a crazy straw, is very effective at transferring heat from the body and cooling the brain. The theropod, on the other hand, has a very short and simple nose and was not as effective at transferring heat away from the brain via its nasal passage.

"The neat thing about this larger study was that it revealed that not only were the enhanced noses of large dinosaurs good at heat exchange, but they worked in a manner that was fundamentally different from what we see in most birds and mammals," said Bourke. "Most large dinosaurs just took their standard, single-channel nose and made it longer and more convoluted."

What remains to be seen is how large dinosaurs such as T. rex kept cool.

"Meat-eating theropods like the T. rex had the same overheating problem that the other large dinosaurs had, but they didn't seem to use their noses to keep their brains cool," said Bourke.

He intends to test a number of theories that claim to answer this conundrum using computational fluid dynamic techniques similar to those he used for the pachycephalosaurs. Bourke and his colleagues' work in this direction may very well prove to be instrumental in solving a long standing mystery in paleontology.