How do we know that dinosaurs RAWR-ed?
That is far from a silly question! I mean, how DO we really know? That’s the hardest part of studying a long-extinct group of animals like dinosaurs: None of us were around when they were around.
When we see dinos in the movies, they always come complete with fearsome roars. From the jerky rubber lizards of the 1940’s to the blood-curdling thunderclap of the T. rex in Jurassic Park, where there’s a saur, there’s a rawr. But those movie roars are created by sound engineers from a mixture of modern sounds. The T. rex shriek in Jurassic Park is actually a mix of the calls from a baby elephant, a tiger and an alligator.
The problem is that the anatomy that animals use to make sounds doesn’t fossilize. Soft tissues like vocal chords and resonating throat sacs don’t last the way bones do. So we have to play dino detective, using a combination of structures that do fossilize and studying reptilian relatives that exist today.
Crocodilian reptiless and birds, two modern evolutionary cousins of dinosaurs, use soft tissues to make noises. The deep groaning vibrations used by crocodiles and reptiles come from the larynx. Much like in our own vocal chords, air from the lungs vibrates folds of tissue to create rather intimidating vibrations that sound like this. Birds, on the other hand … or wing … use a structure called the syrinx, which is close to a larynx but probably evolved independently. That means that roars and rooster calls could have a different evolutionary origin. One, both or neither of those structures may have existed in various families of dinosaurs.
But that’s not the only way dinos made noise. You’ve probably seen this fossil before in a childhood dinosaur book, a hadrosaur:
That large crest on top of the duck-billed head is hollow, like our sinuses. Many paleontologists think that hadrosaurs could have used them as resonating sound chambers to communicate over long distances, like a built-in didgeridoo used to warn of danger. These otherwise average herbivorous dinos, called the “cows of the Cretaceous”, roamed in huge herds (numbering into the thousands), and these sound chambers may have helped them communicate when predators were near.
Of course, we also know that dinosaurs had ears of some kind. Evolution wouldn’t have kept them if they weren’t useful (it’s not quite that simple, actually, but go with me here), and studying those fossilized skull structures may give clues as to what they heard. While we can be sure that they didn’t sound like they do in the movies, the precise nature of Cretaceous cacophony and Triassic tumult may forever remain a mystery. But I’m confident there would have been plenty to hear in the Age of the Dinosaurs.