Tyrannosaurus rex, one of the largest meat-eating dinosaurs on the planet, had an air conditioner in its head, suggest scientists from the University of Missouri, Ohio University and University of Florida. In the past, scientists believed two large holes in the roof of a T. rex’s skull — called the dorsotemporal fenestra — were filled with muscles that assisted with jaw movements. The scientists knew that similar to the T-rex, alligators have holes on the roof of their skulls. Using thermal imaging they examined alligators at a zoological park and found that when it was cooler and the alligators were trying to warm up, the 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 was warmer, the holes appeared 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.