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<p>One of the frustrating things about studying long-extinct animals is how thoughtless they were. Dinosaurs – already factually known to be the creatures of the world – have been terribly bad at the beginning of their study. Instead of lining up in orderly rows under ideal conditions for long-term fossilization, they just <em>died</em> everywhere. This has made it vastly more difficult to study them appropriately. In most cases, fossilization only preserves the bone, though faint markings, scratches, or preserved 'shadows' sometimes still show where soft tissue existed.</p>
<p>Because we can not examine soft tissue directly, we have been able to study the structure of the bone, which has been preserved for millions of years and even with creatures that still exist today. By tracing the evolutionary lineage of still-extinguishing creatures backwards in time when it converges with creatures, scientists can observe how these features evolved</p>
<p>Researchers examining the skull of Tyrannosaurus Rex have published a paper arguing that these creatures actually had air conditioners built into their skulls. Maintaining appropriate body temperature can be a challenge in large animals, and many creatures have different strategies for solving the problem. Elephants have large ears to radiate heat from their airstreams. Some large animals spend a great deal of time in their own body. Some are active mostly at night when temperatures are lower.</p>
<p>Tyrannosaurs, on the other hand, had holes in their skulls. These holes, known as dorsotemporal fenestrae, have long been thought to function as massive anchors for the creature's huge jaw muscles. These muscles were thought to be completely filled when the creatures were alive. According to new research published in <em>The Anatomical Record</em>, however, muscles were not the only thing tyrannosaurs packed into the space. These fenestrae may have served a dual function by providing important cooling capability as well. They write:</p>
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<p>[H]We believe that this is a significant portion of the dorsotemporal fenestra in crocodylians, non-avian dinosaurs, and many other fossil archosaur lineages was not wholly muscular but instead likely housed vascular tissues. When skull roof tissues were elaborated in fossil specimens, evidence indicated that blood vessels were found in the dorsal temporal fossa were often involved in supporting soft tissue cranial display structures … and possibly vascular physiological devices.</p>
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<div id=](https://www.extremetech.com/wp-content/uploads/2019/09/Tyrannosaurus_Rex_Holotype-Feature-640x353.jpg)
Image and caption from "The Frontoparietal Fossa and Dorsotemporal Fenestra of Archosaurs and Their Signi fi cance for Interpretations of Vascular and Muscular Anatomy in Dinosaurs."
Several factors led the paleontologists to this conclusion. For a thing, the anatomical location of the holes made difficult. For another, the bone in this area of the skull is smooth. Attachment points for muscles typically are not. To test their theory, the scientists used to pay attention to the temperatures of the dorsotemporal fenestrae. What they found is that these areas of the body are markedly hotter when the alligator is basking in the sun and cooler when it dozes in the shade.
"Casey Holliday, the leader of the study, says," One of the major physiological challenges that large animals are being able to shed heat National Geographic. "If big theropod dinosaurs were warm-blooded … then they too probably had challenges dissipating heat in some instances."
Other dinosaurs, like ankylosaurs, have been found to have broad, complex nasal passages filled with blood vessels as a means of dissipating heat. Tyrannosaurids lacked this adaptation, which means the creatures – which were as much as 40 feet long and 20 feet tall – had to dissipate heat through some other means. Radiating it outwards from the skull would protect the creature's brain from overheating. National Geographic also noted that some dinosaurs had fenestrae that were close to their neck frills, which are thought to be used in mating and threat signaling. It is possible that Tyrannosaurus Rex or its family members may have been able to use their blood vessels for color-changing displays, however this is strictly a theory of this juncture.
* – As measured by eight-year-old me.
Credit image: Scott Robert Anselmo / Wikimedia Commons
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