Was the Movie "ROAR!" Wrong?
Think back to the first time you saw the Tyrannosaurus rex appear in "Jurassic Park." That iconic "ROAR!" that thundered along with the earth-shaking footsteps is, for many, the definitive sound of a dinosaur. However, recent research suggests that this image may differ from scientific reality.
Soft tissues like vocal cords do not fossilize, so we cannot know the "voice" of a dinosaur directly. So, how do scientists deduce the sounds of the ancient world? The answers lie hidden in the structure of fossilized bones and in the modern-day "relatives" of dinosaurs.
Clue #1: Modern-Day Relatives of Dinosaurs
The most crucial clues to understanding dinosaur vocalizations come from their closest living relatives: birds and crocodilians.
Birds: The Direct Descendants of Dinosaurs
Birds are the direct descendants, having evolved from dinosaurs. The vocal organ that allows birds to produce complex sounds is called the "syrinx." In 2016, the world's first fossilized syrinx was discovered in Antarctica from Vegavis iaai, a close relative of the ancestors of modern birds from the Late Cretaceous. This is significant evidence suggesting that dinosaurs may have made bird-like sounds.
While not all dinosaurs chirped like birds, some smaller ones might have produced sharp calls or tweets similar to modern birds.
What Kind of Sound?
Among birds with a syrinx, more primitive species like ducks and geese make relatively simple "quacking" sounds. This suggests that at least some dinosaurs might have communicated with sharp, bird-like calls or sounds similar to those of ducks and geese.
Crocodilians: Another Important Relative
Crocodilians also share a common ancestor with dinosaurs. They produce a low, rumbling sound from deep in their throats with their mouths closed. This is called "closed-mouth vocalization," and by resonating the sound within their bodies, they create an intimidating, deep bass that travels far.
An increasing number of researchers believe that large carnivorous dinosaurs like Tyrannosaurus may have produced eerie, ground-shaking rumbles with their mouths closed, much like crocodiles. It would have been a sound quieter than a movie roar, yet truly terrifying—a sound that could rattle the very bones of its prey.
Clue #2: The Shape of Fossilized Bones
Bone fossils, especially the structure of the skull, are a valuable source of information for deciphering what kinds of sounds dinosaurs produced and heard.
Parasaurolophus: Nature's Trombone
Parasaurolophus, known for the large crest on its head, is a prime example. CT scans of the crest's interior revealed a complex network of tubes running from the nose, up through the top of the crest, and back down to the nose. It's believed these tubes acted like a trombone, allowing the dinosaur to resonate sound at specific frequencies and amplify it by blowing air through them.
This sound might have been used for communication with mates or as a warning signal. Its tone was likely not a monotonous rumble but a unique, resonant "trumpet-like" call.
Tyrannosaurus: The Inner Ear
Generally, larger animals tend to produce lower-pitched sounds, while smaller animals produce higher-pitched ones. It is unlikely that a 12-meter-long Tyrannosaurus would have chirped like a small bird.
By examining the structure of the inner ear in dinosaur skull fossils, we can infer the frequency of sounds that the dinosaur could hear. Since an animal's hearing is most attuned to the frequencies of its own voice, studying their hearing capabilities allows us to estimate the frequency range of their vocalizations.
Analysis of the Tyrannosaurus's inner ear has revealed that they were particularly adept at hearing low-frequency sounds (infrasound).
It is suggested that Tyrannosaurus did not "roar" like a lion, but instead produced a very low, ground-hugging growl or rumble. This infrasound may have traveled through the air and ground as vibrations.
The Realistic Soundscape of the Dinosaur Era
Based on this scientific evidence, let's imagine the world of the Late Cretaceous period.
- From all corners of the forest, you hear the calls of small, bird-like dinosaurs.
- From a distance, the low, resonant, trumpet-like calls of a Parasaurolophus echoing as it calls to its herd.
- The air trembles as the infrasonic rumble of a Tyrannosaurus travels through the ground.
While it may lack the drama of the movies, the acoustic world of dinosaurs painted by science is more diverse, more subtle, and in some ways, far more terrifying.