Despite its popular image of teeth and nails and thunder, Tyrannosaurus rex had no hot head. A new study shows that two mysterious holes in the top of a dinosaur's skull may have helped regulate temperatures inside his head.
Previously, these holes – called dorsemporal fenestra – were thought to be filled with muscles that helped to operate the powerful jaw. But according to Casey Holiday, an anatomist at the University of Missouri, something did not add up.
"It's really a weird muscle to get out of the jaw, make a 90-degree turn and continue on the roof of the skull," he said. "
" Still, we have a lot of convincing evidence of blood vessels in this area based on our work with alligators and other reptiles. "
Similar fenestra can be found in skulls in a class of animals known as diapsids grouped together because of this characteristic. This class includes not only crocodiles but also birds, lizards and tuatara; holes are thought to have evolved before about 1
Fenestra is not found in all dinosaur skulls, but those who have them include tyrannosaurs and pterosaurs. To begin exploring what these holes are for, the team analyzes various diapsid skulls for to determine which of them has a fenestra most similar to T. rex; the closest similarities are with crocodiles.
So Holiday and his co-authors – William Porter and Lawrence Whitmer of the University of Ohio and Kent Vliet of the University of Florida thermal cameras and went to study a bunch of alligators at St. Augustine Alligator Zoo
Because alligators are cold-blooded or ectothermic, their body temperature depends on their ambient temperature. This means that their thermoregulatory processes are very different from warm-blooded or endothermic organisms.
"We noticed when it was cooler and the alligators were trying to warm up, that is, our thermal image showed big hot spots in those holes in the roof of their skull. which shows an increase in temperature, "Vliet said.
"Yet, later in the day, when it is warmer, the holes look dark, as if they were turned. This is consistent with previous evidence that alligators have a cross-circulatory system – or an internal thermostat, so say. "
It is not yet known whether dinosaurs in general, and T. rex in particular were ectothermic or endothermic.
The topic is actually hotly debated, with some scientists thinking that the first, some the second, and some believing dinosaurs got somewhere between the two – a function called mesothermia. Previous studies have shown that the armored ankylosaurus had tunnels of "crazy straw" in the skull to keep its brain at optimal temperatures.
Now, this study suggests that T. rex (and other dinosaurs) use some of the tactics of thermoregulating ectotherms, but what does this really mean in the wider context of their metabolisms, is yet to be will be investigated.
What scientists can say on the basis of this study is that there are no osteological features on the tyrannosaur skull to indicate that the fenestra was a site of muscle attachment. Based on modern alligators, they can also conclude that fenestra could be used to regulate the temperature in T. the rex skull by warming or cooling blood flowing through blood vessels in structures.
"We know that like T. rex alligators have holes in the roof of their skulls, and they are filled with blood vessels," said Wittmer.
"Yet, for more than 100 years, we have placed muscles in a similar space with dinosaurs. Using the known anatomy and physiology of present animals, we can show that we can overturn these early hypotheses about the anatomy of this part of the skull of T. Rex . "
The team studies were published in The Anatomical Record .