The “extremely rare” discovery of an 80-million-year-old fossilized voice box that belonged to an armored dinosaur reveals that the ancient beast may have sounded more bird-like than experts previously thought, new research suggests.
Pinacosaurus grangeri — a squat, armored, club-tailed ankylosaur found in Mongolia in 2005 — was discovered with the first fossilized voice box (larynx) found in a non-avian dinosaur.
Now, a new analysis, published February 15 in the journal Communication biology (opens in new tab)suggest that the creature’s vocalizations may have been far more subtle and melodic than its previously assumed crocodilian grunts, hisses, rumbles and roars.
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“Our study finds the larynx Pinacosaurus is kinetic and large, similar to birds that make a variety of sounds,” study first author Junki Yoshida (opens in new tab), a paleontologist at the Fukushima Museum in Japan, told Live Science. Dinosaurs are archosaurs, a group whose living members include crocodiles and birds. These animals use sound for a variety of purposes, including courtship, parental behavior, defense against predators, and territorial calls. “So, these are the candidates for its acoustic behavior,” Yoshida said.
At the beginning of the Triassic period, about 250 million years ago, the archosaurs split into two broad groups: a bird-like group that later developed into dinosaursbirds and pterosaursand another group that later branched off into crocodiles, alligators, and a number of extinct relatives.
Most animals that produce sounds do so through specially adapted organs connected to the lungs via the trachea. In crocodiles, mammals, and amphibians, the larynx—a hollow tube located at the top of the windpipe and stuffed with folds of resonating tissue—is adapted to produce sounds. But in birds, the syrinx—a two-tube structure that rests near the lungs, at the base of the trachea—creates the basis for complex melodies.
To assess the range of sounds P. grangeri could have made, the researchers examined two parts of the fossilized larynx that would have worked with muscles to lengthen the airway and change its shape, and compared them to structures in the voice boxes of living birds and reptiles. They found that out P. grangeri had a very large cricoid (a ring-shaped piece of cartilage involved in opening and closing the airway) and two long bones used to adjust its size—a layout that reversed P. grangeri voice box for a vowel modifier.
This anatomical setup probably meant the ancient herbivore was able to make a wide variety of sounds — including rumbles, grunts, roars and possibly even chirps — while roaring over great distances, the researchers said.
That said, ankylosaurs are unlikely to have chirped or squawked like today’s birds, primarily because they were much larger and had very different vocal mechanisms.
“It’s really hard to even begin to deduce what Pinacosaurus sounded like because this is probably a brand new vocal organ that produced its own kind of distinctive sound,” James Napoli (opens in new tab), a vertebrate paleontologist at the North Carolina Museum of Natural Sciences who was not involved in the study, told Live Science. “I think chirping birdsong is unlikely, despite functional similarities to a syrinx, just because of how big ankylosaurs were. In my head, I imagine low, reptilian rumbles and grunts and roars with an intricate birdsong-like complexity.”
The researchers said their future research will focus on narrowing down the possible range of P. grangeri vocalizations while searching for other specimens that may contain preserved larynxes or even a syrinx.
“Dinosaur sounds are one of those persistent unknowns that make this paper even more exciting,” Napoli said. “Without fossilized vocal organs, which are extremely rare, it’s really hard to even begin to estimate the limits of dinosaur vocal behavior, much less what they really sounded like.”