A world-first discovery provides clues to the sounds made by non-bird dinosaurs: ScienceAlert

In a prehistoric forest some 80 million years ago, a stocky, 16-foot-long armored dinosaur with a spiny back on four short legs ambles, slowly munching on a snack of plant matter.

After swallowing, the flap of skin in its throat blocking its vocal box flips back open, allowing the dinosaur to take a deep breath and make a terrifying…


That’s not exactly the scariest beginning of a scene in the next Jurassic World movie, but it might be more realistic than a roar.

Soon after the fossilized body of a Cretaceous named ankylosaurs Pinacosaurus grangeri Discovered in 2005 in Mongolia’s Gobi desert basin, its beautifully preserved larynx bones were thought to play a role in breathing.

Now paleontologists from Hokkaido University Museum in Japan and the American Museum of Natural History suggest they do in fact form key parts of its vocal box, the first ever discovered in a non-avian dinosaur.

Despite the animal’s relatively distant relationship with birds, the larynx shares some similarities with modern tweeters and chirps. In fact, the vocalizing anatomy appears to be an odd hybrid of reptile and bird larynxes, the researchers say.

About 250 million years ago, reptilian-like animals on Earth called archosaurs split into two groups: one with dinosaurs and pterosaurs, and another with crocodiles and alligators.

An ankylosaur like Pinacosaurusresearchers say, might have sounded like something between those two lineages.

“It’s pretty safe to assume that dinosaurs make crocodile-like sounds,” said paleontologist Victoria Arbor, who wasn’t involved with the study New York Times.

“That’s the basic anatomy they would be working with. And then birds have evolved these additional ways of making sounds that allow them to more nuancedly modify the sounds coming out of their throats.”

Artwork ankylosaurs
Artistic rendering of Pinacosaurus with internal view of the larynx. The cricoid can be seen in purple, while the green represents the arytenoid cartilage, which helps produce sound. (Art by Tatsuya Shinmura)

The larynx is a hollow tube that sits at the top of the throat and contains anatomical features that are adapted to produce sound waves. When air is exhaled through the tube, folds of tissue vibrate at specific frequencies.

This is how mammals, amphibians and reptiles make noise with their airways.

But birds are an odd exception. They have a “syrinx” located at the opposite end of the trachea to a larynx. For humans, it would be like having a voice box in your chest.

A bird’s syrinx has two separate “tubes” that allow them to make two different calls at the same time. Birds also have another structure that sits higher up in their windpipes, allowing them to further modulate the sounds they make lower down.

The whole network is quite complex, and yet scientists still don’t really understand how it evolved from a larynx.

Modern birds are descended from avian dinosaurs, and yet because the vocal box is made of soft tissue, very few ancient specimens have been found in fossil form. The oldest bird syrinx ever found is 66 million years old and closely resembles what geese and ducks have today.

However, no fossilized larynx has ever been reported in a non-avian archosaur.

dinosaur larynx
The larynx-like structure in the skull of Pinacosaurus; md = lower jaw, lcr = left cricoid cartilage, rcr = right cricoid cartilage, atr = arytenoid process. (Photo by Michael D’Emic, edited by Junki Yoshida)

The Pinacosaurus fossil characteristics a ring-shaped piece of cartilage in the larynx, called cricoid cartilage, which is particularly large. Larger, the researchers say, than what is normally seen in the larynx of living reptiles.

Nowadays, reptiles that are louder tend to possess larger cricoids, meaning the size of this cartilage is a good indication of sound.

Compared to modern day turtles, lizards, crocodiles and birds, researchers say so Pinacosaurus has an elongated larynx. Unlike reptiles, this suggests that the dinosaur would not have used its larynx as a sound source but as a sound transducer.

Today, living birds modify sounds with a different structure, but in a similar way.

“Therefore,” researchers write, “the larynx is Pinacosaurus may have been actively vocalized and associated with loud and explosive calls as in vocal reptiles and birds.

The authors have not yet said what these are Pinacosaurus‘ Voice actually sounded like it, but they think his vocalizations were likely “related to courtship, parental call, anti-predation, and territorial calls” and may have included coos and chirps.

However, even if this dinosaur had a larynx more akin to living reptiles, bearing no resemblance to a bird’s syrinx, it’s possible it could still make bird-like sounds.

The voices of turtles and other reptiles have been seriously overlooked by scientists in the past. Many of these creatures are simply thought of as mute, when in fact they can make an amazing variety of sounds, including cooing, croaking, chirping, grunting, clicking, and even meowing!

Apparently, researchers are still working on how the larynx and syrinx differ in their sound-producing abilities.

Without further evidence, who says prehistoric ankylosaurs couldn’t even have sounded like cats?

Now that is an opening to the next Jurassic World that audiences weren’t expecting.

The study was published in communication biology.

Leave a Reply

Your email address will not be published. Required fields are marked *