(SOUNDBITE OF DINOSAUR ROARING)

LINDA WERTHEIMER, HOST:

That is the familiar sound of a dinosaur roar - well, at least that's what Hollywood has led us to believe over the years. But what if a dinosaur actually sounded like this?

(SOUNDBITE OF DINOSAUR COOING)

WERTHEIMER: According to new research, that cooing is much more likely what a dinosaur sounded like. Julia Clarke is a professor of paleontology and the lead author of a new study that may debunk the dinosaur's roar. She joins me now from KUT in Austin, Texas. Welcome to our program.

JULIA CLARKE: It's my pleasure.

WERTHEIMER: We've been going on the assumption - I suppose largely from movies - that dinosaurs made a big noise. They're such big creatures. Why do you think we're wrong.

CLARKE: Most dinosaur sounds are based on models that are more like lions and tigers and bears. And we know that the two groups of animals alive today that are most closely related to extinct dinosaurs are birds and crocodilians. In fact, birds are living dinosaurs.

WERTHEIMER: So you look at the way birds make noises?

CLARKE: Exactly. That's what we did in this particular study. We looked at one aspect of vocal behavior, which is whether the mouth is open or closed. And we looked at living dinosaurs - birds. We have 10,000 species today. Most of them vocalize, sing with an open mouth. But some birds produce sound with a closed mouth. They actually inflate different structures that allow them to resonate, often at lower frequencies than many other birds. But we also needed to look at alligators and crocodiles as the closest cousins to dinosaurs.

WERTHEIMER: Well, I have actually heard alligators bellow and make a terrific noise.

CLARKE: Well, exactly, and that bellow is a closed-mouth sound. So when we think of our T. rex, we don't need to imagine just simple cooing. But there are a variety of generally low frequency sounds that are produced in this way.

WERTHEIMER: Do you think there are other things about dinosaurs that we've gotten wrong for a long time?

CLARKE: Well, for many, many years, we imagined dinosaurs as these scaly, you know, green kind of slick guys.

WERTHEIMER: Reptilian.

CLARKE: Reptilian, exactly, and now we know that many species of dinosaurs had feathers or simple filaments that seem to be feather precursors in some cases.

WERTHEIMER: Do your findings come from the relatively recent discovery that some dinosaurs had feathers? Is this sort of, like, the next step?

CLARKE: We are sort of taking the next. In the last 10 years, we've discovered that we can gain insight into the colors of dinosaurs and how they may have used visual signals in important contexts. And so what we wanted to ask is, can we gain insight into the vocal communication that extinct dinosaurs might have had?

WERTHEIMER: Well, so what's next for you in your research?

CLARKE: There's a lot more to study. For example, living birds, they essentially sing from the heart. Their vocal organ is deep in the chest. And we and crocodiles, our vocal folds are in our mouth. So we don't know when this transition occurred. And my collaborators include physiologists and developmental biologists, and we're looking at this question of how we get birdsong and how we get the vocal organ of birds in time. So that's where I'm excited to go next. We're going to find out a lot more about this, I think, in the next couple years.

WERTHEIMER: Julia Clarke is a paleontologist at the University of Texas in Austin. She joined me from KUT in that city. Miss Clarke, thank you very much.

CLARKE: Oh, it's a pleasure to be here. Transcript provided by NPR, Copyright NPR.

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