How did the biggest dinosaurs stay cool? With built-in air conditioning

20 Dec 2018402 Views

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Image: © David Biagi/Stock.adobe.com

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Researchers have helped solve the mystery of how giant dinosaurs stayed cool in sweltering climates.

We know that as humans, when we start to overheat, our body releases sweat in order to cool us down. But spare a thought for ancient dinosaurs whose large, armoured bodies had to navigate climates where sweltering heat was the norm.

So, how did these gigantic creatures stay cool? This question has long perplexed researchers as, while the dinosaurs were adept at retaining heat, their size alone would have put them at risk of overheating even on a cloudy, mild day.

Now, a team led by palaeontologist Jason Bourke from the New York Institute of Technology has suggested the answer could lie within their noses. Aside from their primary function as something used to smell, noses are also important heat exchangers, ensuring that air is warmed and humidified before it reaches the delicate lungs.

In birds and mammals, this process is achieved using thin curls of bones and cartilage within nasal cavities called turbinates, which increase the surface area and allow for air to come into greater contact with the nasal walls.

Using computed tomography scanning and an engineering modelling approach called computational fluid dynamics, the team simulated how air moved through the nasal passages of two different ankylosaur species, including the hippo-sized Panoplosaurus and larger rhino-sized Euoplocephalus.

The team saw how, without turbinates, the two dinosaurs evolved to have longer, coiled noses with just as much efficiency at warming and cooling as what we have. In the Panoplosaurus, the researchers saw its nasal passages were longer than the skull itself; they were twice as long, coiled up within the skull, in Euoplocephalus.

Diagram showing the nasal air-conditioning in Euoplocephalus.

Nasal air conditioning in Euoplocephalus. Image: Jason Bourke/NYITCOM at A-State

‘Like a child’s crazy-straw’

To see whether nasal passage length was the reason for this efficiency, Bourke ran alternative models with shorter, simpler nasal passages that ran directly from the nostril to the throat, as in most other animals. The results clearly showed that nose length was indeed the key to their air conditioning ability.

“When we stuck a short, simple nose in their snouts, heat transfer rates dropped by over 50pc in both dinosaurs. They were less efficient and didn’t work very well,” Bourke said.

Also, by reconstructing blood vessels based on bony grooves and canals, the team found a rich blood supply running right next to these convoluted nasal passages. When the hot blood from the body core would travel through these blood vessels, it would transfer their heat to the incoming air. Simultaneously, evaporation of moisture in the long nasal passages cooled the venous blood destined for the brain.

The study’s co-author, Lawrence Witmer from Ohio University, said: “A decade ago, my colleague and I published the discovery that ankylosaurs had extremely long nasal passages coiled up in their snouts. These convoluted airways resembled a child’s ‘crazy-straw’ – completely unexpected and seemingly without reason, until now.”

The researchers now want to examine other dinosaurs to determine when this nasal enlargement happened.

Colm Gorey is a journalist with Siliconrepublic.com

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