The mystery of the weird holes in T. Rex's head could finally be solved

Despite his popular image of teeth and claws and thunder, Tyrannosaurus rex was not hot-headed. New research indicates that the two mysterious holes at the top of the dinosaur's skull probably helped regulate the temperatures inside his head.

Previously, it was assumed that these holes, called dorsotemporal windows, were filled with muscles that made the powerful jaw work. But, according to anatomist Casey Holliday of the University of Missouri, something did not go well.

"It's really strange for a muscle to come out of the jaw, make a 90-degree bend and skirt the roof of the skull," he said.

"Yet, we now have a great deal of irrefutable evidence of the presence of blood vessels in this region, based on our work with alligators and other reptiles."

Similar fenestras can be found in the skulls of an animal class called diapsids, grouped together because of this feature. This class includes not only crocodilians, but also birds, lizards and tuatara; Holes are thought to have evolved about 300 million years ago.

There are no fenestra in all dinosaur skulls, but those with some include tyrannosaurs and pterosaurs. To determine the usefulness of these holes, the team analyzed different skulls of diapside to determine which ones had the highest resemblance. T. rex; the closest similarities were found to be with crocodilians.

For example, Holliday and his co-authors – William Porter and Lawrence Witmer of Ohio University and Kent Vliet of the University of Florida – took thermal imaging cameras and went to study a group of alligators at the park. Zoological Museum St Augustine Alligator Farm.

Because alligators are cold-blooded or ectothermic, their body temperature depends on the temperature of their environment. This means that their thermoregulation processes are very different from warm-blooded or endothermic organisms.

"We noticed that when it was colder and the alligators were trying to warm up, our thermal imaging showed big hot spots in those holes in the roof of their skull, indicating an increase in temperature," he said. declared Vliet.

"Still, later in the day, when it's warmer, the holes look dark, like they've been turned off to stay cool." This is consistent with previous evidence that alligators have a system. cross-flow circulatory – or an internal thermostat, so to speak. "

(Holliday et al., The Anatomical Record, 2019)

We do not know yet whether dinosaurs in general, and T. rex in particular, were ectothermic or endothermic.

The subject is currently the subject of lively debate, with some scientists thinking that the first, some last, and other believing dinosaurs found themselves somewhere in between – a feature called mesothermal. Previous research has suggested that the armored ankylosaur has "crazy straw" tunnels in his skull to help keep his brain at optimal temperatures.

Now, this research suggests that T. rex (and other dinosaurs) use some of the thermoregulatory tactics of ectotherms, but what this actually means in the broader context of their metabolisms has not yet been explored.

What scientists can Tell, based on this research, is that there are no osteological features on the skull of the tyrannosaur that would indicate that the window was a site of muscle attachment. They can also deduce, based on modern alligators, that fenestra could have been used to regulate the temperature in the kiln. T. rexof the skull, warming or cooling the blood flowing through the blood vessels of the structures.

"We know that, just as the T. rex, the alligators have holes on the roof of their skull and they are filled with blood vessels, "Witmer said.

"Yet for over 100 years, we have been implanting muscles in a space similar to that of dinosaurs.Using a bit of anatomy and physiology of current animals, we can show that we can reverse the first assumptions about the Anatomy of this part of the T. rexis the skull. "

The research of the team was published in The anatomical file.