5 SEP 2019

Despite its popular image of teeth and claws and thunder, Tyrannosaurus rex was no hot-head. New research indicates that the two mysterious holes in the top of the dinosaur’s skull likely helped regulate temperatures inside its head.

Previously, these holes – called the dorsotemporal fenestra – were thought to be filled with muscles that helped operate the powerful jaw. But, according to anatomist Casey Holliday of the University of Missouri, something didn’t quite add up.

“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,” he said.

“Yet, we now have a lot of compelling evidence for blood vessels in this area, based on our work with alligators and other reptiles.”

Similar fenestra can be found in the skulls of a class of animals known as diapsids, grouped together because of this feature. This class includes not only crocodilians, but also birds, lizards, and tuatara; the holes are thought to have evolved about 300 million years ago.

Fenestra are not found in all dinosaur skulls, but those that do have them include tyrannosaurs and pterosaurs. To start figuring out what these holes were for, the team analysed different diapsid skulls to determine which ones had fenestra most simi

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