Dinosaurs Didn’t Roar Like in ‘Jurassic World’: Some Were Capable of Singing Like Birds

The soundtrack of the dinosaur era remains a mystery. The roars of Tyrannosaurs and the cries of Velociraptors in movies — such as in the fourth installment of Jurassic World, releasing this week — are purely inventions of sound engineers aiming to thrill audiences. These supposed dinosaur sounds have settled into popular imagination, while scientists could do little more than speculate. Since the vocal apparatus of these animals comprises soft tissues that rarely fossilize, until quite recently, scientists could only imagine what dinosaur sounds might have been like based on the structures they had for perceiving sound and certain crests and ornaments on their skulls that could serve as resonating chambers. That is all changing.

The Parasaurolophus tubicen, which lived 70 million years ago, may have sounded like a ship’s horn or an Australian didgeridoo thanks to its unique cranial ornament, as shown in a scientific recreation from the New Mexico Museum of Natural History (USA). In 1995, paleontologists from that museum recovered a fossil of this hadrosaurid with a massive crest nearly a meter long that protruded from the back of its head.

Like a prehistoric wind instrument, within this unique structure were three pairs of hollow tubes that extended from the nose to the top of the crest, which researchers scanned in detail using a computed tomography similar to that of a CT scan. After two years of work, the result was computer simulations of how that organ would resonate if air were blown through it, reconstructed digitally with the help of computational scientists. “I would describe the sound as otherworldly. I remember it gave me chills,” recently stated Tom Williamson, one of those paleontologists, to the BBC.

No one knows for sure how the vast diversity of dinosaurs that existed throughout the Mesozoic sounded. The soundscape would have been different in each of the three stages of the more than 180 million years that comprise it, but science has made some attempts. Based on the shape of the inner ears and other cranial cavities, scientists have developed theories about how that group of extinct reptiles could have sounded.

If the aim was to communicate and warn of dangers, the hearing ability of dinosaurs would have to have been subordinated to that function; their small auditory structures must have perceived low frequencies, much like modern crocodiles do. It is presumed that animals perceive the types of sounds they can produce themselves. No screams or roars. It is more likely that most large dinosaurs emitted low, long-wavelength sounds capable of traveling vast distances and making the ground vibrate. A low amplified hiss, something akin to a monstrous ancestor of the Italian opera singer Cesare Siepi, regarded as one of the best lyrical basses of the 20th century.

However, imagination must strive in another direction that reduces the fear of some of these prehistoric beasts’ sounds. Until recently, sharp calls and high-frequency sounds were believed to be the domain of birds, but in 2023, a discovery emerged from the sands of the Gobi Desert (Mongolia) that changed everything.

It was a fossilized larynx of the ankylosaur Pinacosaurus grangeri — a three-ton quadrupedal herbivore almost two meters tall and about five long — which led to the idea that singing could also originate from wingless animals. “This is the first discovery of a vocal organ from non-avian dinosaurs in the long history of research on them. It is interesting that the larynx of the Pinacosaurus is similar to that of modern birds, so it likely used it to modify sound as birds do, instead of the vocalization typical of reptiles. Therefore, we can say that the Pinacosaurus basically sounded similar to birds,” states Japanese paleontologist Junki Yoshida, the lead author of this finding, which was published in the journal Nature.

The larynx is made of cartilages, a type of soft tissue that microorganisms and environmental erosion easily disintegrate, making its natural preservation over millions of years exceptional. Hence, paleontology has relied on other resources to attempt to reconstruct something as intangible as sound. “The sound communication of dinosaurs had been studied solely through the inner ear of the fossil skull, but not through the vocal organ itself,” explains Yoshida, showcasing pride in his work. “Therefore, my discovery of the larynx represents a completely new way and a more direct approach to studying the sound communication of dinosaurs.”

Awakening to the Song of a Dinosaur

On the other side of sound — and the world — Argentine paleontologist Ariana Paulina Carabajal, an expert in sensory biology at the National Scientific and Technical Research Council (CONICET), works on cranial structures to uncover how those extinct animals saw, heard, and moved to do what all living beings do: survive every day. “What do animals use sound for? Basically, to communicate with each other and to warn of dangers, but very little is known about sound production.”

The conclusions derived from the larynx of Pinacosaurus coincide with those drawn by Paulina Carabajal, in Canada and Mongolia, Turkey, while studying a part of the inner ear of dinosaurs of the same family. “I studied one of the two ankylosaurs in which the cochlea — a fundamental auditory structure — was preserved, and when I reconstructed it, they were among the largest I had found until now. Very long, much more than in other dinosaurs. Generally, their cochleas are the same size as those of modern crocodiles; they don’t change much, but ankylosaurs have wider cochleas. So we think that they may have somewhat increased their range of sound perception. Always at low frequencies because all dinosaurs tended to hear low frequencies. Now, associated with this discovery from Gobi, it makes sense. We understand that for some reason, they heard a little differently than other dinosaurs. They had some specialization for vocalization. It’s interesting because it changes the interpretation of the entire ankylosaur group and raises the question: what other dinosaurs could have had a similar development?”

It is tempting to get excited about the implications of the findings. Venturing a little, the scientist believes that being appealing prey for large carnivores, it is not unreasonable to think that those armored creatures could produce high-pitched sounds imperceptible to their predators. But she acknowledges that reality is not always as linear as that reasoning and that, therefore, there are other aspects to consider.

Paleontologist Federico Agnolín, a researcher at CONICET and the Azara Foundation, worked ten years ago on another discovery linked to prehistoric sound: an exceptionally preserved syrinx from a species of duck that went extinct 70 million years ago was the first direct evidence of what the vocal apparatus typical of the birds that coexisted with the last dinosaurs was like. In light of Yoshida’s discovery, he proposes a bold reconstruction. “The vocal repertoire of that dinosaur is somewhere between that of songbirds and parrots. It’s not that we think it sounded like an eagle, no. Perhaps it was more like a thrush that would wake up in the morning and start singing.”

For him, imagination should be unleashed. “The problem is that we have a whole legacy of previous research that we can’t get out of our heads. So one keeps imagining a Tyrannosaurus rex as a gigantic reptile, although its relatives from which we have fossils that preserved their skin show they were covered in proto-feathers, something akin to fur. Suppose the whole body was covered in fur, but we’re still unable to imagine a T. rex that way.”

More cautiously, Paulina Carabajal sets limits on creativity. “What should not be directly interpreted from Yoshida’s work is that by emitting sounds like a bird, it had song. It wouldn’t be like the beautiful songs that birds make, but more like a rattling sound related to how air flowed through the larynx.” This is a different instrument than that of birds, which instead have a syrinx, a unique organ that allows them to produce those songs so appreciated by humans. “Reptiles have protruding tissue folds — they displace — into the space where air exits, and when they move, they generate sounds, hisses, but most reptiles do not produce vocalization. One thing is to make a sound, and another is proper vocalization.” That’s why the case of the Pinacosaurus from the Gobi Desert is so surprising. Its discoverers highlight that it and its relatives could indeed vocalize.

The larynx of this ankylosaur consists of two parts like that of any reptile, but with the peculiarity that there was mobility between those two pieces, allowing it to control the air coming in and out, producing sounds similar to those of some birds.

Re-evaluating Many Fossils

The tongue of reptiles is not as mobile as that of mammals; being attached to the bottom of the jaw, its movements are greatly restricted, leaving only the tip free, hindering it from manipulating food. What is particularly interesting about the Pinacosaurus, according to Paulina Carabajal, is that “very large hyoid cartilages were also found, which support the tongue — essential for swallowing, breathing, and producing sounds. Therefore, the authors propose that this tongue was much more mobile than in other dinosaurs and might have allowed it to manipulate food a bit when grabbing it.”

For Agnolín, surprises may arise in specific cases. “We need to re-evaluate many remains. Dinosaurs appear that have some pieces in their necks that are not well understood. We need to see if they are syrinxes or similar structures.” Erosive factors particularly limit certainty. “The syrinx is composed of several ossified cartilages that interweave and form something like a small drum. When the animal dies, it falls apart and decays. So if you find a piece of a drum from a syrinx, which should be 2 millimeters, you wouldn’t recognize it,” laments the Argentine scientist.

Studies like his and that of Pinacosaurus, however, invite the revisitation of deposits to search for fragments that were not identified at the time to evaluate the possibility that they may be sound clues. It is something he has already done and regrets not having found matches. Agnolín suspects that in many cases it will also be necessary to overcome human bias. “Perhaps there are some researchers who deny that this is a syrinx and will talk about other structures. All of this takes time and is part of the eternal scientific debate.”

The consensus among paleontologists is that, with these perspectives and the technological advances being made, solving the mystery of dinosaur sound is closer than ever. Reconstructing the soundtrack of the Mesozoic is just a matter of time.