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You probably remember the T.rex’s iconic roar from Jurassic Park, but it turns out that dinosaurs actually didn't sound that ferocious.

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Sources:
https://news.utexas.edu/2016/10/12/oldest-known-squawk-box-reveals-dinosaurs-likely-didn-t-sing
http://www.nature.com/nature/journal/v538/n7626/full/nature19852.html
http://www.vulture.com/2013/04/how-the-dino-sounds-in-jurassic-park-were-made.html
https://news.utexas.edu/2016/07/11/dinosaurs-may-have-cooed-like-doves
http://onlinelibrary.wiley.com/doi/10.1111/evo.12988/abstract
http://www.smithsonianmag.com/science-nature/did-dinosaurs-roar-48438337/
http://www.tandfonline.com/doi/abs/10.1080/08912960903033327
http://www.smithsonianmag.com/science-nature/when-helmet-head-was-a-neccessity-not-a-fashion-faux-pas-32371556/

Image Sources:
https://commons.wikimedia.org/wiki/File:Crocodilia_collage.jpg
https://commons.wikimedia.org/wiki/File:BirdSyrinx_DolphinNasalComplex.jpg
[♩INTRO] I think we all remember the T. rex from Jurassic Park and its iconic roar.

But that impressive sound effect was actually made using a recording of a baby elephant, and it probably sounds, nothing like a real dinosaur. If you want to know what dinosaurs might have sounded like, one place to start is with their closest living relatives: birds and crocodilians, which are crocodiles and their cousins.

These two groups of animals have different vocal organs, which means their vocal abilities probably evolved after the two groups split off from each other. Crocodilians have larynxes, which are in their throats, and contain vocal folds that vibrate to produce sound. And birds have syrinxes further down in their chests, which are basically tiny chambers surrounded by an air sac.

Their most recent common ancestor—which would have also been an ancestor of the dinosaurs—wouldn’t necessarily have had either of those things. It’s hard for us to know because vocal organs are made of soft tissues. They usually decay instead of being replaced with minerals and becoming a fossil.

Parts of ancient bird syrinxes sometimes fossilize, but we’ve never found any fossil structure resembling a syrinx with fossil dinosaur bones. So dinosaurs probably didn’t warble or sing like modern birds, it’s probably good for the Jurassic Park movies and we don’t have evidence of larynxes and roaring either. But the types of sounds that birds and crocodilians can both make might have popped up in dinosaurs.

Animals in both groups show aggression by hissing, which doesn’t even use vocal organs. It’s basically just exhaling really loudly. So maybe dinosaurs hissed, kinda like angry geese.

And one specific type of sound production called closed-mouth vocalization has evolved in both groups multiple times. The mechanics vary from species to species, but generally it’s a low-pitched sound that’s made by pushing air through a pouch in the trachea or esophagus, rather than through an open beak or mouth. The most familiar example of this is probably a pigeon cooing, but large birds like ostriches also bulge out their necks and use these sounds to communicate.

And so do crocodiles. If birds do it and crocodilians do it, then maybe dinosaurs made these grumbly bellows too. So next time you re-watch Jurassic Park, mentally replace all those mighty roars with hisses and booms and you’ll probably have something a little closer to reality.

This doesn’t mean dinosaurs were any less cool… just a little weirder than you may have thought. Thanks to Patreon patron Fr. Jay for asking, and, really, thanks to all of our patrons because we wouldn’t be able to make these videos without you.

If you’d like to submit questions to be answered, you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!