For many years, dinosaurs have been depicted as great hulking animals, flicking out their tongue from between their gnashing teeth like a lizard might. But this is most probably wrong. A new study has found that dinosaurs such as the Tyrannosaurus rex likely wouldn't have been able to stick out its tongue.
Publishing their results in PLOS One, a team of researchers compared the hyoid bone from dinosaurs with their closest-living relatives and found that their mouth anatomy would have had been closer to that of a crocodile than a bird.
“They've been reconstructed the wrong way for a long time,” explains Professor Julia Clarke, from UT Jackson School of Geosciences, in a statement. “In most extinct dinosaurs their tongue bones are very short. And in crocodilians with similarly short hyoid bones, the tongue is totally fixed to the floor of the mouth.”
While we obviously can’t dissect a real dinosaur, we can infer what their soft tissue might have looked like by comparing the underlying bones with those of living counterparts.
In most animals – such as you and me – the hyoid bone acts like an anchor to the tongue, only attached to other bones by muscles and ligaments. But in birds and some reptiles, the hyoid bone is slightly different and extends forward, running through the tongue to form a solid bony support.
Because dinosaurs sit in a group that includes not only crocodiles and alligators but also birds, the team looked at the hyoid bones of extinct dinosaurs and pterosaurs and then compared them with the hyoid bones found in modern birds and alligators. They then assessed how they related to the soft tissue and muscles that cover them.
By taking high-resolution images of the hyoid bone and the muscles in three different alligators and 13 different bird species, the researchers could build a detailed picture of how all the structures related to one another. These were then used as a reference for fossil dinosaurs as diverse as small, bird-like animals to the massive theropod Tyrannosaurus rex, with a few pterosaurs thrown in.
They found that the structure of the hyoid in dinosaurs most closely matched that of alligators, implying that, like the crocodilians, their tongues would have been firmly attached to the floor of their mouth. Interestingly, however, the pterosaur hyoid morphology showed otherwise and was seemingly as diverse as that of birds.
The scientists suggest that perhaps by taking to the skies, the animals lost the ability to manipulate food with their hands. This led to greater diversity in feeding techniques, and thus increased the mobility of the tongue.