Tyrannosaurus Rex, Dinosaur

In a movie such as Jurassic Park, dinosaurs are often depicted as roaring ferociously, but a new at the University of Texas, Austin suggests that dinosaurs didn’t roar. Instead, they made slightly less intimidating coos and mumbles (like modern birds), and had a special way of emitting sound known as closed-mouth vocalizations.

Closed-mouth vocalizations are sounds that are produced through the skin in the bird’s neck area after air is pushed through an esophageal pouch while the beak is kept shut the whole time. Unlike the high-pitched chirps produced from open beak of songbirds, the closed-mouth sounds are much quieter and lower in pitch. Birds make closed mouth vocalizations usually to attract mates or to defend their territory, but at other times they produce sound through an open mouth.

“Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized,” said Chad Eliason, the study’s co-author in a statement. They found that not all birds has the same closed-mouth vocalization, but it has evolved at least 16 times in archosaurs – a group that includes birds, dinosaurs and crocodiles. And, they think it could have evolved in dinosaurs as well.

Today’s birds are living dinosaurs. Researchers suspect that they may have mating rituals similar to modern birds and communicated in a similar way. However, the study can’t yet provide enough evidence to prove what dinosaurs really sounded like because vocal organs do not fossilize the way their bones do. Even if they do, the fossil records can’t prove it. Moreover, based on what researchers know about birds, dinosaurs likely had air sacs instead of vocal cords. In future, the researchers hope to integrate information from information from fossils, experimental physiology, gene expression and sound modeling. This way, it wouldn’t be so hard for researchers to understand the sounds that extinct early avian species produced. The findings have been published in the journal Evolution.

Reference: Coos, booms, and hoots: The evolution of closed-mouth vocal behavior in birds.