In a prehistoric forest, some 80 million years ago, a stocky, 5-meter-long, spiny-backed armored dinosaur strolls about on four short legs, slowly chewing on a morsel of plant material.
After it swallows, the flap of skin in its throat opens that blocks the voice box, allowing the dinosaur to take a deep breath in and let out a fearsome…
It’s not exactly the scariest start to a scene in the next Jurassic World movie, but it might be more realistic than a roar.
Right after the fossilized body from a Cretaceous period ankylosaur named Pinacosaurus grangeri was discovered in the Gobi Desert Basin of Mongolia in 2005, its amazingly preserved clavicle was thought to play a role in breathing.
Now paleontologists from the Hokkaido University Museum in Japan and the American Museum of Natural History suggest that they actually make up important parts of the voice box, the first ever to be discovered in a non-avian dinosaur.
Despite the animal’s relatively distant relationship to birds, the larynx has several similarities to modern tweeters and chirps. In fact, the vocalizing anatomy appears to be a strange hybrid between the voice boxes of reptiles and birds, the researchers say.
About 250 million years ago, reptile-like animals on Earth, called archosaurs, split into two groups: one containing dinosaurs and pterosaurs, and another containing crocodiles and alligators.
An ankylosaur that Pinacosaurussay researchers, may have sounded like something in between these two lineages.
“Assuming that dinosaurs make some crocodile-like sounds is pretty safe,” said paleontologist Victoria Arbour, who was not involved in the study. New York Times.
“That’s the basic anatomy they would work with. And then birds developed these additional ways of producing sounds where they can modify the sounds coming out of the throat in a more nuanced way.”
The larynx is a hollow tube that sits at the top of the throat and contains anatomical features adapted to produce sound waves. When air is exhaled through the tube, folds of tissue vibrate at specific frequencies.
This is one way mammals, amphibians and reptiles produce noise with their respiratory tract.
But birds are a curious exception. They have a ‘syrinx’ located at the opposite end of the trachea to a larynx. For humans, it would be like having a ballot box in your chest.
The syrinx of a bird has two separate “tubes”, which allow them to make two different calls at the same time. Birds also have another structure higher up in their trachea that allows them to modulate the sounds they produce deeper down.
The entire network is quite complex, and yet scientists do not understand how it evolved from a larynx.
Modern birds are descended from avian dinosaurs, and yet because the voice box is made of soft tissue, very few ancient examples have been found in fossil form. The oldest bird syrinx ever found is 66 million years old and is very similar to what geese and ducks have today.
Until now, however, a fossilized larynx has never been reported in a non-avian archaeosaur.
The Pinacosaurus fossil features a ring-shaped piece of cartilage in the larynx known as a cricoid, which is particularly large. Larger, say the researchers, than what is usually seen in the larynx of living reptiles.
Today, reptiles that are more vocal tend to have larger cricoids, meaning that the size of this cartilage is a good indicator of sound.
Compared to modern turtles, lizards, crocodiles and birds, scientists say that Pinacosaurus has an elongated larynx. Unlike reptiles, this suggests that the dinosaur would not have used the larynx as a sound source, but as a sound modifier.
Today, living birds modify sound using a different structure, but in a similar way.
“Therefore,” scientists write, “the larynx to Pinacosaurus may have been actively vocalized and associated with loud and explosive calls as in vocal reptiles and birds.”
The authors are not yet prepared to say what Pinacosaurusactually sounded like, but they believe the vocalizations were probably “related to courtship, parental calls, predator defense and territorial calls” and may have included coos and chirps.
However, even if this dinosaur had a larynx more similar to that of living reptiles, with no resemblance to a bird’s syrinx, it is possible that it could still make bird-like sounds.
The voices of turtles and other reptiles have been seriously overlooked by researchers in the past. Many of these creatures are simply assumed to be mute, when in fact they can make an astonishing variety of sounds, including coos, croaks, chirps, grunts, clicks and even meows!
Clearly, researchers are still working to determine how the larynx and syrinx differ in their sound-producing abilities.
Without more evidence, who’s to say that prehistoric ankylosaurs couldn’t have even sounded like cats?
Now it is an opening to the next Jurassic World that audiences wouldn’t expect.
The study was published in Communication biology.