The most famous dinosaurs in history is perhaps the mighty Tyrannosaurus rex, so famous that their colossal structure has become an icon of the prehistoric era. Scientists have recently stated the theory that their huge, blocky head had a system of air conditioning built in.
The findings have been published in the journal Anatomical Record.
Large animals need special ways to cool down, since their immense body heat can overwhelm them in hot conditions.
There were two large holes in the skull of these beasts that were previously thought to have been filled by muscles. But now the theory is that these holes acted as a kind of internal "air-conditioning unit," to help the dinosaur lose heat.
Scientists say it is more likely this area was filled with blood vessels that helped the T-Rex regulate its temperature.
Casey Holliday, from the University of Missouri, and colleagues, used thermal imaging devices to examine alligators at the St Augustine Alligator Farm Zoological Park in Florida.
"It's really hard to get a picture of an alligator skull in the wild, because they're always off away from you and they are dangerous to approach," he said.
Being at the farm made the researchers' work easy, as they only had to get up over the fence and take images and videos they needed.
Through this research they discovered that the alligators have blood-vessel-filled holes in their skulls. Their body heat depends on the environment, explained study co-author Kent Vliet, from the University of Florida in Gainesville.
"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 is warmer, the holes appear dark, like they were turned off to keep cool," Kent explained.
By examining fossils and 3-D images of Tyrannosaurus Rex's skull, the scientists discovered that the dinosaur had similar holes as the gators.
In the past, scientists believed the two large features in the roof of the extinct predator's skull - called the dorsotemporal fenestra - were filled with muscles that assist with jaw movements.
But Casey thought it was really weird for a muscle to come up from the jaw, make a 90-degree turn, and go along the roof of the skull. They now know this area is full of blood vessels. T Rex appears to have had similar structures in its skull.
Casey Holliday argued that, for active predator, as the T Rex probably was, at some point, they had to be able to shed heat, as well as hold on to heat. Having a bed of capillaries in the skull roof provides a mechanism for these types of animals to collect heat or shed heat.