Tech – Metro | Dinosaurs evolved incredible cooling systems to beat heat waves, research shows

Dinosaurs evolved to cool themselves during heat waves (Shutterstock)

Large dinosaurs evolved incredibly complex internal cooling systems as a way to beat the heat, according to scientists.

These cooling systems – a kind of dino air conditioning – were different from those of smaller creatures.

That's because larger dinosaurs (just like elephants today) were more vulnerable to warm temperatures.

Now, cutting-edge 3D imaging has identified multiple heat exchangers that controlled their brain's 'thermostat'.

Lead author Professor Ruger Porr said: 'The brain and sense organs like the eye are very sensitive to temperature. Animals today often have elaborate thermoregulatory strategies to protect these tissues by shuttling hot and cool blood around various networks of blood vessels. We wanted to see if dinosaurs were doing the same things.'

Famous gigantic dinosaurs such as the long-necked sauropods or armoured ankylosaurs evolved big bodies independently from smaller-bodied ancestors.

Co-author Professor Lawrence Witmer said: 'Small dinosaurs could have just run into the shade to cool off. But for those giant dinosaurs, the potential for overheating was literally inescapable.

'They must have had special mechanisms to control brain temperature, but what were they?'

Professor Porter said: 'One of the best ways to cool things down is with evaporation. The air-conditioning units in buildings and cars use evaporation, and it's the evaporative cooling of sweat that keeps us comfortable in summer.

'To cool the brain, we looked to the anatomical places where there's moisture to allow evaporative cooling, such as the eyes and especially the nasal cavity and mouth.'

So the researchers, from Ohio University, looked to the modern-day relatives of dinosaurs – birds and reptiles. This showed evaporation of moisture in the nose, mouth, and eyes cooled the blood on its way to the brain.

The researchers obtained carcasses of birds and reptiles that had died of natural causes from zoos and wildlife rehabilitation facilities. Using a special CT scanning technique that highlights arteries and veins, they traced blood flow from the sites of evaporative cooling to the brain.

They also precisely measured the bony canals and grooves that conveyed the blood vessels.

Prof Porter said: 'The handy thing about blood vessels is that they basically write their presence into the bones. The bony canals and grooves that we see in modern-day birds and reptiles are our link to the dinosaur fossils.

'We can use this bony evidence to restore the patterns of blood flow in extinct dinosaurs and hopefully get a glimpse into their thermal physiology and how they dealt with heat.'

'Dippy' is the famous Diplodocus fossil shown here at the Natural History Museum in 2017 (Getty)

The findings published in Anatomical Record show 'one size didn't fit all' with regard to how large-bodied dinosaurs kept their brains cool. Smaller dinosaurs such as the goat-sized pachycephalosaur Stegoceras had a very balanced vascular pattern with no single cooling region being particularly emphasised.

Prof Porter said: 'That makes physiological sense because smaller dinosaurs have less of a problem with overheating. But giants like sauropods and ankylosaurs increased blood flow to particular cooling regions of the head far beyond what was necessary to simply nourish the tissues.'

This unbalanced vascular pattern allowed the thermal strategies of large dinosaurs to be more focused.

Sauropods like Diplodocus and Camarasaurus emphasised both the nasal cavity and mouth as cooling regions – and ankylosaurs such as Euoplocephalus only the former.

Prof Porter said: 'It's possible that sauropods were so large – often weighing dozens of tons – that they needed to recruit the mouth as a cooling region in times of heat stress.'

One problem that the researchers encountered was that many of the theropod dinosaurs – such as the 10-ton T Rex – were also gigantic. But the analysis showed they had a balanced vascular pattern – like the small-bodied dinosaurs. Prof Witmer said: 'This finding had us scratching our heads until we noticed the obvious difference – theropods like Majungasaurus and T Rex had a huge air sinus in their snouts.'

Looking closely at the bones showed it was richly supplied with blood vessels – pumping air in and out every time the animal opened and closed its mouth.

Prof Witmer added: 'Boom! An actively ventilated, highly vascular sinus meant we had another potential cooling region. Theropod dinosaurs solved the same problem – but in a different way.'

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