Study suggests T-Rex had an air conditioner in its head

No matter how much we learn about dinosaurs, there is always something more to discover. And a group of researchers is giving us more knowledge about the fearsome Tyrannosaurus Rex (T-Rex) by arguing that it had an air conditioner in its head.

No, not a literal air conditioner. That would be amazingly weird, but the air conditioner they reference is a vascular apparatus that keeps a reptile from overheating.

After all, reptiles are cold-blooded and overheating would be a major problem unless they find a way to regulate their body temperature.

As we all know, the T-Rex last walked the Earth around 65 million years ago before the dinosaurs were wiped out by a mass extinction event resulting from an asteroid slamming into our planet.

Scientists have uncovered more than 50 major specimens, many of which are nearly complete skeletons, so we know that T-Rex was one of the largest apex predators to have ever lived and reached a height of 40 feet.

But there is something bizarre about the T-Rex head that has been debated among scientists for years, because there are some pretty mysterious and gnarly holes in the skull. Obviously, two of the holes are eye sockets. But the two at the top of the head don’t have such a clear purpose.

A T-Rex skull at the Field Museum of Natural History in Chicago. You can see the two holes at the top of the skull. Image via Wikimedia.

According to scientists from the University of Missouri, Ohio University and University of Florida, most scientists hypothesize that the holes housed muscles that controlled the jaw, which may have been the most powerful jaw with the strongest bite force in history.

“The attachments of jaw muscles are typically implicated in the evolution and shape of the dorsotemporal fenestra on the skull roof of amniotes,” the researchers noted in their study, published by the American Association for Anatomy. “However, the dorsotemporal fenestrae of many archosaurian reptiles possess smooth excavations rostral and dorsal to the dorsotemporal fossa which closely neighbors the dorsotemporal fenestra and jaw muscle attachments. Previous research has typically identified this region, here termed the frontoparietal fossa, to also have attachment surfaces for jaw‐closing muscles.”

But the team, consisting of MU School of Medicine professor of anatomy Casey Holliday, University of Florida Department of Biology coordinator of laboratories Kent Vliet and Ohio University Heritage College of Osteopathic Medicine professor of anatomy Larry Witmer, say that the space is more likely to have been a cooling center to control temperature.

Relevant anatomical features argue for rejection of the default hypothesis—that the fossa was muscular—due to a complete lack of osteological correlates reflective of muscle attachment. The most‐supported inference of soft tissues is that the frontoparietal fossa contained a large vascular structure and adipose tissue. Despite the large sizes and diverse morphologies of these fossae found among dinosaur taxa, these data suggest that non‐avian dinosaurs had the anatomical foundation to support physiologically significant vascular devices and/or vascular integumentary structures on their skull roofs.

To make this conclusion, the team needed to study a living relative of T-Rex, and it turns out that we have lots of them swimming around today in the form of alligators and crocodiles, the reptile with the most powerful bite force in the world today.


An American alligator in Florida emerges from the water. Image via Wikimedia.

So, the team traveled to St. Augustine Alligator Farm Zoological Park in Florida, where they used thermal imaging to analyze the skulls of living alligators.

Using thermal imaging, the team observed that when crocodiles are trying to cool down the two holes that make up their dorsotemporal fenestra are dark as if its been turned off. And when they are heating back up the dorsotemporal fenestra is no longer dark, but a bright light as shown on the imaging.


Thermal imaging on this camera shows a bright light emanating from the top of the alligator’s skull between the eyes, indicating that it is heating up. Image via University of Missouri.

It turns out that alligators, crocodiles and other reptiles have what is known as a cross-current circulatory system that allows them to control their internal body temperature at will. The two holes observed at the top of their skulls houses this vascular apparatus. And it’s likely T-Rex had the same anatomical ability.

“An alligator’s body heat depends on its environment,” Vliet said in a statement to Mizzou News. “Therefore, we noticed when it was cooler and the alligators are trying to warm up, our thermal imaging showed big hot spots in these holes in the roof of their skull, indicating a rise in temperature. Yet, later in the day when it’s warmer, the holes appear dark, like they were turned off to keep cool. This is consistent with prior evidence that alligators have a cross-current circulatory system—or an internal thermostat, so to speak.”

What a T-Rex skull may have looked like under the thermal imaging. Notice the bright light at the top indicating that T-Rex is warming up much like alligators do today. Image via University of Missouri/Brian Engh

Organic air conditioners

In short, an organic air conditioner, which is why it’s strange that it took so long for scientists to make the connection.

“It’s really weird for a muscle to come up from the jaw, make a 90-degree turn, and go along the roof of the skull,” Holliday said in reference to the previous T-Rex hypothesis. “Yet, we now have a lot of compelling evidence for blood vessels in this area, based on our work with alligators and other reptiles.”

Witmer agrees.

“We know that, similarly to the T-Rex, alligators have holes on the roof of their skulls, and they are filled with blood vessels,” he said. “Yet, for over 100 years we’ve been putting muscles into a similar space with dinosaurs. By using some anatomy and physiology of current animals, we can show that we can overturn those early hypotheses about the anatomy of this part of the T-Rex’s skull.”

For years, scientists also failed to see the similarities between birds and dinosaurs, and now they are digging up specimens that still have intact feathers, which means dinosaurs still live among us today as modern-day birds just as much as they do as modern-day reptiles like alligators.

Continuing our study of dinosaurs and learning more about them may be as simple as studying the living species that are closest to them. And then we can finally put to rest some of the lingering mysteries about dinosaurs we have been trying to solve for many decades.

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Featured Image: T-Rex from Pixabay altered in Photoshop

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