But when you turn to face the scaly beast, it opens up its mouth and lets out little peeps, like a robin.
Based on a fossil from a Pinacosaurus grangeri, paleontologists think that some large dinosaurs might have chirped like birds, not roared like lions.
The fossil is the first intact larynx bone from a dinosaur ever found, the scientists said in their study which was published in the journal Nature earlier this year.
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The "unique and beautiful" specimen is part of a voice box, Junki Yoshida, a paleontologist at Hokkaido University Museum in Japan who led the research, said in a presentation at the American Museum of Natural History on Tuesday.
How they found the bone and discovered its purpose
When this small triangular fossil was originally discovered in the Gobi desert in 2005, Yoshida said, the researchers identified it as part of an Ankylosaurus dinosaur called Pinacosaurus grangeri.
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They initially thought the bone they found was used in a different part of the dinosaur's throat, for breathing, Yoshida said.
However, after comparing the fossil to a hundred breathing bones of similar species, they weren't satisfied that they had it right.
It's at this point that Yoshida thought that the bone might be part of a different structure.
When he started analyzing the specimen against the voice boxes of birds related to dinosaurs, it all fell into place — the bone wasn't used to help the dino breathe, it was used to help it make noise, he said.
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Why is this the first time they found this bone
It's rare for researchers to find fossils from voice boxes because they're made partially of cartilage, which usually deteriorates over time.
The only bones of this sort that they've found before have been from birds, not from reptilian dinos.
Though there's still more that researchers have to understand in order to determine exactly how the dinosaurs would've vocalized Yoshida said, "This is the first step to understand dinosaur voices."
