Being a gigantic dinosaur presented some challenges, such as overheating with the Cretaceous sun and that your brain is frying. Researchers from the University of Ohio and NYITCOM in the state of Arkansas, United States, show in a new article posted on 'PLOS ONE'And picked up by Europa Press, that the ankylosaurs heavily armed and with garrotte tail They had a kind of 'air conditioning' in their snouts.
"The huge bodies that we see in most dinosaurs must have become very hot in the hot climates of the Mesozoic," explains the study's lead author, Jason Bourke, an assistant professor at the School of Osteopathic Medicine at the New York Institute of Technology in the State of Arkansas. "Brains do not like that, so we wanted to see if there were ways to protect the brain from cooking. It turns out that the nose can be the key, "he adds.
Bourke and the team used computed tomography and a powerful engineering approach called computational fluid dynamics for simulate the way air moved through the nasal passages of two different species of ankylosane, the 'Panoplosaurus' the size of a hippopotamus and the 'Euoplocephalus' larger than a rhinoceros, to test how well ankylosaurs transferred heat from the body to the inhaled air.
"A decade ago, my colleague Ryan Ridgely and I published the discovery that ankylosaurs had incredibly long nasal passages rolled up in their snouts," says study co-author Lawrence Witmer, a professor at the Ohio University School of Osteopathic Medicine. "These convoluted airways looked like a twisted straw for children! It was completely unexpected and I asked for an explanation. I was thrilled when Jason approached the problem as part of his doctoral research in our laboratory, "he adds.
"This project is an excellent example of how advances in CT scanning, 3D reconstruction, imaging, and computational fluid dynamics modeling can be used in biological research to test long-term hypotheses," says Kathy Dickson. , direct programs at the National Science Foundation that funded the research. "From these new images and models, fossils can provide additional information about extinct organisms such as ankylosaur, in this case, offering an explanation of how unusual characteristics actually work physiologically," he adds.
Smelling can be a primary function of the nose, but the noses are also heat exchangers, making sure that the air warms up and humidifies before it reaches the lungs. To achieve this effective air conditioning, birds and mammals, including humans, rely on thin loops of cartilage and bone within their nasal cavities called turbinates, which increase the surface area, allowing the air to come in contact with more of the nasal walls.
«The ankylosaurs they had no turbinates, but had very long and twisted noses », says Bourke. When the researchers compared their findings with data from live animals, they discovered that the noses of dinosaurs were just as efficient for heating and cooling the air breathed. "It is a case of nature that finds a different solution to the same problem," says Bourke.
Regarding how long these nasal passages were, in 'Panoplosaurus', they were a little longer than the skull itself and in 'Euoplocephalus', they were almost twice as long as the skull, so they are wrapped in the snout. To see if the length of the nasal passage was the reason for this efficiency, Bourke made alternative models with shorter and simple nasal passages that ran directly from the nostril to the throat, as in most other animals.
The results clearly showed that the length of the nose was the key to its ability to act as air conditioning. «When we put a short and simple nose in their snouts, Heat transfer rates fell more than 50 percent in both dinosaurs. They were less efficient and did not work very well, "Bourke describes. Another line of evidence that these noses were air conditioners that helped cool the brain came from blood flow analysis.
"When we reconstruct blood vessels, based on grooves and bone channels, we find a rich supply of blood right next to these convoluted nasal passages," describes another of the study's authors, Ruger Porter, professor at the Faculty of Osteopathic Medicine. from the University of Ohio. "The warm blood from the body's core would travel through these blood vessels and transfer their heat to the incoming air. Simultaneously, the evaporation of the moisture in the long nasal passages cooled the venous blood destined for the brain », Add.
So, why the need for these efficient heat exchangers? The large bodies of 'Panoplosaurus' and 'Euoplocephalus' They were really good at retaining the heat, which is good to stay warm, but it is bad when the animals need to cool down. This problem of heat release would have put them at risk of overheating even on cloudy days. In the absence of some protective mechanism, the delicate neural tissue of the brain could be damaged by the warm blood of the body's nucleus.
"Sure, their brains were almost comically small," says Bourke. But they are still their brains and they need protection. " The complicated nasal passages of these dinosaurs acted as conditioners to cool the brain with a constant flow of cooled venous blood, allowing them to keep their heads cold at all times. This feat of natural engineering could also have allowed the evolution of large sizes of so many dinosaurs.
"When we look at the nasal cavity and air passages in dinosaurs, we find that more elaborate noses are found in large dinosaur species, suggesting that the physiological stresses of large body size may have stimulated some of these anatomical novelties to help to regulate the temperature of the brain, "says Witmer.
The next step for the researchers is to examine other dinosaurs to determine when this nasal enlargement occurred. "We know that the big dinosaurs had these crazy airways, but exactly what size did this happen? says Bourke. Was it a gradual development as the size of the body increased, or is there a threshold size at which an ordinary nose can no longer do the job? We do not know". EP