History Stories

Time to update our image of the dinosaur with a giant tongue protruding from its terrifying jaws. That tongue was stuck to its mouth.

When you picture Tyrannosaurus rex, the most fearsome of all the dinosaurs, you probably imagine it with jaws gaping, a giant tongue protruding from its terrifying mouth.

But according to a new study published in PLOS ONE, that isn’t how T. rex looked at all. In fact, many dinosaurs couldn’t stick out their tongues, which were rooted to the floors of their mouths, like those of alligators.

To reach this surprising conclusion, scientists from the University of Texas at Austin and the Chinese Academy of Sciences studied the hyoid bones of modern birds and alligators and compared them with fossils including extinct bird-like dinosaurs, pterosaurs (flying reptiles of the Jurassic and Cretaceous periods) and a Tyrannosaurus rex. Hyoid bones are the bones in the neck that anchor and support the tongue in most animals, though in birds they can extent to the tip of the tongue.

Fossils of T. rex heads discovered in Northeast China revealed that a bone, called the hyoid, resembled those of alligators. The blue and green arrows are pointing to the hyoid apparatus. (Credit: Li et al. 2018)

Fossils of T. rex heads discovered in Northeast China revealed that a bone, called the hyoid, resembled those of alligators. The blue and green arrows are pointing to the hyoid apparatus. (Credit: Li et al. 2018)

What they found was that the hyoid bones of T. rex and most other dinosaurs matched up best with those of alligators. They were short, simple and not very mobile, compared with the more diverse hyoid bone shapes shown in the pterosaurs, flying dinosaurs and living birds.

So much for those dramatic depictions of dinosaurs, with their gaping mouths and huge waving tongues. “They’ve been reconstructed the wrong way for a long time,” study co-author and Jackson School Professor Julia Clarke said in a press release announcing the new research. “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.”

This is not the first dino myth Clarke has worked to debunk: She also co-authored a 2016 study that found dinosaurs likely made birdlike sounds (such as coos and hoots) that bear little resemblance to the mighty roars of popular imagination.  

Clarke and her colleagues in the new study suggest that the greater diversity of hyoid bone shapes among pterosaurs, bird-like dinosaurs and modern birds might be related to their ability to fly, and the related evolution of front limbs from hands into wings. The lack of hands might have meant that flying dinosaurs would have had to evolve greater tongue mobility in order to manipulate prey better with their mouths.  

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