Dinosaur noses enhanced smelling, cooled brain

Dinosaurs used their noses to not only breathe but also to enhance the sense of smell and cool their brains, according to a new study.

Researchers led by Ohio University used high-powered computer simulations to model how air flowed through the noses of modern-day dinosaur relatives such as ostriches and alligators.

"Once we got a handle on how animals today breathe the tricky part was finding a good candidate among dinosaurs to test our methods," said    doctoral student Jason Bourke, lead author of the new study.

Researchers turned to pachycephalosaurs, or "pachys," a group of plant-eating dinosaurs best known for the several-inch-thick bone on the top of their skulls.
They found that building the extra skull bone resulted in ossifying soft tissues in other areas of the body - such as the nose.

"When we cleaned up the fossil skull of Sphaerotholus, a pachy from North Dakota, we didn't expect to see these delicate scrolls of bone in the nasal region. We knew they must be nasal turbinates," said Emma Schachner, a co-author on the study from Louisiana State University.

Similar structures were found in a different pachy species from Canada called Stegoceras by co-author Phil Bell from the University of New England in Australia.

The first nasal turbinates to be discovered were in the back part of the nasal cavity, called the olfactory chamber, where smelling takes place.

The olfactory region of the brain in Stegoceras was quite large, which, along with the large olfactory turbinates, suggested that Stegoceras had a good sense of smell.
But when Bourke ran his airflow simulation analyses, the inspired air bypassed the olfactory chamber.

Researchers then focused on a long bony ridge on the wall of the front of the nasal cavity.

In the modern-day relatives of dinosaurs, cartilaginous nasal turbinates often attach to such ridges, suggesting to the team that pachys may have had turbinates in the front, respiratory part of the nasal cavity.

When Bourke digitally inserted respiratory turbinates of different shapes the computer airflow simulations made sense.

"Some of the restored airflow patterns now carried odours to the olfactory region. We don't really know what the exact shape of the respiratory turbinate was in Stegoceras, but we know some kind of baffle had to be there," said Bourke.

The research suggests that turbinates have important functions as baffles to direct air to the olfactory region. They might play another critical role - cooling the brain.

Study co-author Ruger Porter, another Ohio University doctoral student, has been studying the pattern of blood flow in pachycephalosaurs and other dinosaurs.

"The fossil evidence suggests that Stegoceras was basically similar to an ostrich or an alligator," Porter said.

"Hot arterial blood from the body was cooled as it passed over the respiratory turbinates, and then that cooled venous blood returned to the brain," Porter said.