New discovery shows how T. rex kept his brain cool

To avoid overheating, large animals such as elephants and rhinos had to devise strategies to stay cool. Dinosaurs love Tyrannosaurus rex probably the same problem – and new research finds that huge carnivores solved it by developing giant air conditioners in their heads.

Researchers led by Casey Holliday examined large holes in the top of carnivorous dinosaur skulls called dorsotemporal windows. A careful anatomical study revealed that the cavities probably contained tissues rich in fat and blood vessels.

These structures may have been helpful in venting heat into the environment when the dinosaurs were too hot and absorbed heat when they were cold, the team reports in the newspaper. The anatomical file.

"We discovered that large theropod dinosaurs, and even some of the smaller ones, like Velociraptor"These types of pouches probably contain blood vessels and are useful for heat regulation," says Holliday, a paleontologist at the University of Missouri's School of Medicine.

For more than a century, paleontologists have thought that these holes made it possible to hold the jaw muscles of species such as T. rex, since at the dinosaurs and their living relatives, the birds, the depressions are just in front of the big openings of the muscle of the jaw.

"Almost everyone has assumed that these muscles were simply prolonged," says Thomas Holtz, an expert in tyrannosaurs from the University of Maryland College Park, who was not one of the authors of the ############################################################################### 39; study.

But when Holliday studied these cranial spaces in dinosaurs, alligators and other animals, the old explanation was not taken into account. On the one hand, if the space anchored T. rex Jaw muscles, the muscle should have come out of the jaw, take a 90-degree bend, and then meander along the roof of the skull. In addition, the smooth surface of the bone suggests that the muscle fibers and tendons do not attach to it.

Instead, when researchers studied the anatomy of modern alligators and birds, among the closest living relatives of non-avian dinosaurs, they found that these animals tended to fill the area with fat and blood vessels. As with the heat exchanger of an air conditioner, the structure could have allowed the blood to radiate or absorb heat from the environment.

To test their interpretation, researchers used thermal imaging cameras to observe modern alligator heads at the Zoological Park at Alligators Farm in St. Augustine, Florida. The images showed that at different times of the day, the area of ​​the skull containing the dorsotemporal windows was relatively warmer or cooler than the rest of the animal's head, depending on whether the animals needed to dissipate or recover heat.

"One of the main physiological problems of large animals is to be able to dissipate heat," says Holliday. "If the big theropod dinosaurs had warm blood … then they probably also had trouble dissipating the heat in some cases."

For large theropod dinosaurs such as T. rexLarge cooling structures in the head would have been extremely helpful in maintaining a constant brain temperature, especially if they were getting too hot.

"You can not cook a brain or an egg either," says Holtz.

In related work, paleontologist Jason Bourke of the New York Institute of Technology discovered in 2018 that a group of armored dinosaurs called ankylosaurs could have large convoluted nasal passages filled with blood vessels. As the animals breathed, these vessels would have helped to dissipate the excess heat in the environment. Bourke says the new research is compelling, especially since his team has not found evidence of similar extension of nasal passages in carnivorous theropods.

"This new study suggests another way that theropods could regulate the temperature of their brains and their eyes," he says.

Holliday hopes the results will lead other people to test the hypothesis of the cooling structure. It is also possible that a concentration of blood vessels in this region of the skull could also have helped support the display structures on the heads of some dinosaurs.

In extinct dinosaurs, the structures may even have been proportionally larger than those seen in live animals, Holliday points out. And in theropods such as T. rex, ship-filled structures would have covered a large area above the head. Holliday also points out that some horned dinosaurs, such as Triceratops and Chasmosaurus, have signs of similar structures in their skull roofs that are terribly close to the flourishes of their necks.

Dinosaurs may have used these vessel networks for changing color displays, "even though it was as simple as scales that whiten and whiten with the underlying blood flow," says Bourke.