Dinosaurs almost certainly made sounds, but those sounds were probably nothing like the thunderous roars Hollywood has trained us to expect. The emerging picture from fossil anatomy and living relatives points toward something more surprising: many dinosaurs likely produced deep, closed-mouth vocalizations resembling booms, coos, and rumbles rather than open-mouthed screams. The evidence comes from a handful of exceptionally preserved fossils, the acoustics of bizarre cranial structures, and careful comparisons with the two groups of animals that bracket dinosaurs on the evolutionary tree: crocodilians and birds.
Why Dinosaur Sounds Are So Hard to Pin Down
The fundamental problem is that sound-producing organs are made of soft tissue, cartilage, and membrane, none of which fossilize easily. The vocal folds, throat pouches, and nasal passages that shape an animal’s voice leave almost no trace in stone. The syrinx, the unique vocal organ that lets modern birds sing, was not even known from fossils older than a few million years until researchers described the first Mesozoic specimen from a Late Cretaceous bird found in Antarctica, dating to roughly 66 to 69 million years ago.1PubMed. Fossil evidence of the avian vocal organ from the Mesozoic That discovery also hinted at something important: the absence of syrinx fossils in non-avian dinosaurs may not be an accident of preservation. A complex syrinx appears to have been a relatively late innovation in bird evolution, arising well after flight itself. If most dinosaurs lacked a syrinx, they would have relied on a different structure, the larynx, to shape whatever sounds they made.
This is a crucial distinction. Birds produce their songs and calls using the syrinx, located deep in the chest where the trachea splits into the two bronchi. Crocodilians, lizards, and most other reptiles use a larynx at the top of the throat, more like mammals do. For decades, researchers assumed non-avian dinosaurs fell on the larynx side of this divide, but there was no direct fossil evidence to confirm it. That changed in 2023.
A Fossilized Larynx Changes the Conversation
Researchers studying the ankylosaur Pinacosaurus, a tank-like herbivore from the Late Cretaceous of Mongolia, found something remarkable: preserved, ossified laryngeal cartilages, specifically the cricoid and arytenoid, the two structures that form the core of the voice box. These bones were not just present; they were large, firmly jointed, and built in a way that closely resembles the larynx of modern birds like parrots and songbirds rather than the simpler arrangement seen in crocodilians and turtles.2PubMed Central. An ankylosaur larynx provides insights for bird-like vocalization in non-avian dinosaurs
The key feature is what the joint allowed the animal to do. In crocodilians, the glottis (the opening between the vocal folds) stays nearly closed during sound production, and vibration of the folds themselves generates the noise. In birds, the glottis opens wide because the sound source is the syrinx farther down, and the larynx acts more like a filter or modifier, shaping the sound after it is produced. The Pinacosaurus larynx had the bird-like arrangement: a large arytenoid process and a firm joint that would have let it swing the glottis open easily, suggesting it was built to modify airflow and shape sound rather than to generate sound by fold vibration alone.2PubMed Central. An ankylosaur larynx provides insights for bird-like vocalization in non-avian dinosaurs The researchers concluded that this larynx was specialized for acoustic communication, not merely for keeping food out of the airway, since simple airway protection does not require such a large and mobile structure.
What kinds of sounds might Pinacosaurus have produced? The study’s authors suggest vocalization related to courtship, parental calls, predator defense, and territory, the same broad categories seen in modern archosaurs.2PubMed Central. An ankylosaur larynx provides insights for bird-like vocalization in non-avian dinosaurs That does not tell us the pitch or timbre, but it does tell us that at least some non-avian dinosaurs had vocal hardware sophisticated enough to support a range of communicative sounds.
Closed-Mouth Booms and Rumbles
If you have ever heard a pigeon coo, an ostrich boom, or a bittern produce its eerie pumping call, you have heard a closed-mouth vocalization. The animal inflates a throat pouch or esophageal sac and resonates sound through it without opening the beak. The result is a low-frequency, often booming sound that carries well over distance. A study mapping vocal behavior across the bird family tree found that closed-mouth vocalizations have evolved independently at least 16 times in birds and tend to show up in larger-bodied species, where bigger resonating chambers produce deeper, more impressive sounds.3Evolution. Coos, booms, and hoots: The evolution of closed‐mouth vocal behavior in birds
The relevance to dinosaurs is direct. The same study noted that crocodilians, the closest living relatives of birds, also use both open- and closed-mouth vocalizations in different contexts, with closed-mouth sounds used specifically in territorial and display calls.3Evolution. Coos, booms, and hoots: The evolution of closed‐mouth vocal behavior in birds Since closed-mouth vocalization is present in both surviving branches of the archosaur family tree, the most parsimonious conclusion is that it was likely present in the ancestors that connect them, including non-avian dinosaurs. The researchers specifically suggested that closed-mouth vocalization may have been present in dinosaurs and, following the pattern in living animals, was probably associated with display, sexual selection, and larger body size.4Oxford Academic. Coos, booms, and hoots: The evolution of closed‐mouth vocal behavior in birds
Think about what that means for a sauropod or a large theropod. A closed-mouth vocalization from an animal weighing several tons, pushing air through a resonating chamber scaled to that body, would have produced profoundly deep, rumbling sounds, perhaps more felt than heard, like standing near a subwoofer. Not the shrieking roar from the movies. More like the infrasound that elephants use to communicate over kilometers.
The Parasaurolophus Trombone
Some dinosaurs went beyond soft-tissue resonators and carried their acoustic equipment on the outside. The hadrosaur Parasaurolophus, with its dramatic backward-sweeping hollow crest, has long been suspected of using that structure as a resonating chamber. The crest contains looping nasal passages that air would have traveled through before reaching the lungs, and their shape strongly resembles a musical instrument.
Recent experimental work using a physical model of the crest confirmed the acoustic hypothesis. Researchers built a scaled replica and ran frequency sweeps through it, finding a fundamental resonant frequency around 800 Hz with peaks at its multiples. Some of those peaks were shifted compared to a control, and the model showed non-linear acoustic behavior at certain frequency ranges, which is exactly what you would expect from a complex resonating tube rather than a simple pipe.5The Journal of the Acoustical Society of America. Acoustic characteristics of Parasaurolophus crest: Experimental results from a physical model An 800 Hz fundamental sits roughly in the range of a low tuba note, a deep, resonant sound. With harmonics stacking on top, the call of a living Parasaurolophus may have had an eerie, brassy quality that carried across Cretaceous floodplains.
Different species of lambeosaurine hadrosaurs had differently shaped crests, from the hatchet-like crest of Corythosaurus to the rounded dome of Lambeosaurus. If the crests functioned as resonating chambers, each species would have produced a distinct sound, essentially walking around with species-specific bugles on their heads. This could have helped individuals recognize their own kind in mixed herds, the acoustic equivalent of distinctive plumage.
What Crocodilians Reveal
Since no one can put a microphone in the Cretaceous, the next best thing is to study the animals that shared a common ancestor with dinosaurs and still live today. Crocodilians are the only surviving non-bird archosaurs, and they are far from silent. Alligators and crocodiles hiss, bellow, growl, and produce infrasonic vibrations that visibly ripple the water around them.
Chinese alligators provide a particularly interesting case. Researchers studying their bellowing choruses found that both males and females participated, remaining mostly still while synchronizing their calls. The choruses lasted about ten minutes with sharp start and stop times. Playback experiments showed that both sexes responded equally to calls from either sex, and none of the tested animals approached the speaker, suggesting the bellowing was not about competing for mates directly. Instead, the researchers proposed the choruses function to assemble scattered individuals into the same area for subsequent mating, essentially a group-location broadcast.6PubMed. Why do Chinese alligators (Alligator sinensis) form bellowing choruses: a playback approach
This is worth sitting with for a moment. If modern crocodilians use coordinated vocal displays to locate each other over distance, some dinosaurs may have done the same. A herd of hadrosaurs calling back and forth across a valley, or a group of large theropods using low-frequency booms to establish spacing in dense forest, are not wild speculation. They are reasonable inferences drawn from what the closest living relatives actually do.
Listening to the Inner Ear
You can learn a lot about what an animal sounds like by figuring out what it was built to hear. If a species has ears tuned to low frequencies, it almost certainly produces low-frequency sounds, because hearing and vocalization co-evolve. Fortunately, the inner ear is encased in bone, and bone fossilizes beautifully.
Researchers have shown that the length of the endosseous cochlear duct, the bony channel that houses the hearing organ, can predict an animal’s mean hearing frequency and range. Longer ducts correlate with broader hearing ranges, and duct length also tracks with vocal complexity and social behavior in living reptiles and birds.7PubMed Central. Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds This gives paleontologists a way to infer the general acoustic world of an extinct animal from a CT scan of its skull.
A broader analysis of inner ear shape across archosaurs found something striking about the cochlea. There was a single evolutionary elongation event on the stem lineage leading to all archosaurs, both the branch that became crocodilians and the branch that became dinosaurs and birds. The researchers interpreted this as coinciding with the origin of high-pitched juvenile calls, the kind of location, alarm, and hatching-synchronization sounds that baby crocodilians and baby birds both make, along with the adult ability to respond to those calls.8PubMed. The early origin of a birdlike inner ear and the evolution of dinosaurian movement and vocalization In other words, the acoustic world of baby dinosaurs calling to their parents and parents answering back may have been established very early in archosaur evolution, long before the particular vocal anatomy of any specific dinosaur lineage evolved.
Picture a nesting ground. Dozens of hatchlings peeping in high-pitched, insistent calls. Adults rumbling back in low, closed-mouth responses. The acoustic texture of that scene is not purely imaginary. It is constrained by real anatomical evidence from the inner ears of both groups.
What About T. Rex?
The animal everyone wants to hear is Tyrannosaurus rex, and frustratingly, it is one of the hardest to reconstruct. No laryngeal or tracheal soft tissue has been found for any large theropod. We are left with inference.
A few things can be said with reasonable confidence. First, T. rex was enormous, and in living animals, body size strongly predicts the fundamental frequency of vocalizations. Bigger animals make deeper sounds. A twelve-meter-long predator would have had a very long trachea, and the resonant frequency of that tube would have been extremely low. Second, based on the closed-mouth vocalization research, large-bodied dinosaurs were the most likely candidates for booming, resonant, closed-mouth calls. Third, T. rex almost certainly lacked a syrinx, since that organ appears to be a late bird innovation, so it would have relied on its larynx and possibly inflatable throat structures to generate sound.
The upshot is that a vocalizing T. rex probably sounded less like a lion and more like a vastly scaled-up alligator bellow or an ostrich boom: deep, reverberant, possibly subsonic, and felt in the chest before it registered in the ears. The iconic movie roar, which was famously cobbled together from recordings of a baby elephant, a tiger, and an alligator, is pure invention. Entertaining, but almost certainly wrong about the character of the sound.
The Tongue and Throat Problem
Sound production is not just about the vocal organ. The shape of the mouth, the mobility of the tongue, and the architecture of the throat all affect what comes out. Here, the fossil record offers a mixed picture. A comparative study of hyoid bones, the skeletal elements that anchor the tongue and throat muscles, found that most non-avian dinosaurs had surprisingly simple hyoid structures that showed limited modification even across major changes in diet and body size.9PubMed Central. Convergent evolution of a mobile bony tongue in flighted dinosaurs and pterosaurs Only in derived ornithischians (the group including hadrosaurs and ceratopsians), pterosaurs, and birds did the hyoid become elaborate enough to support a truly mobile tongue.
This matters because tongue mobility affects how an animal can shape its vocal tract. A dinosaur with a simple, relatively fixed tongue would have had fewer options for modulating sounds once they were produced. It could still vary pitch by changing airflow and tension in the larynx, and it could still resonate sound through nasal passages or inflatable sacs, but the rapid, fine-grained articulation that birds use to produce complex songs would have been out of reach for most species. Hadrosaurs, with their more elaborate hyoid apparatus and their resonating crests, may have been among the most acoustically sophisticated non-avian dinosaurs.
How Movies Get It Wrong (and Why It Matters Less Than You Think)
Film sound designers are not trying to reconstruct paleobiology. They are trying to make you feel something in a theater. The Jurassic Park roars work because they tap into primal fear responses calibrated by millions of years of mammalian evolution, associating loud, high-energy sounds with large predators. Real dinosaur sounds, if we could hear them, might be more unsettling in a different way: low-frequency rumbles you feel in your ribcage, eerie tonal calls echoing through hollow crests, synchronized bellowing choruses reverberating across wetlands.
The scientific reconstruction of extinct soundscapes is still in its early stages. Researchers have noted that the sounds of dinosaurs and other charismatic vertebrates are not definitively known because their vocal organs rarely preserve well, making any reconstruction provisional. But “provisional” does not mean “groundless.” Each new fossil discovery, like the Pinacosaurus larynx, each new acoustic model, like the Parasaurolophus crest experiments, and each new comparative study of living archosaurs narrows the range of plausible sounds. The picture that is forming is quieter, deeper, and stranger than popular culture has prepared us for.
Dinosaurs That May Have Been Silent
Not every dinosaur necessarily vocalized. Some may have communicated primarily through visual displays, body language, or mechanical sounds like foot-stomping, tail-slapping, or the clacking of bony armor. Modern animals offer plenty of precedent: many lizards and turtles are largely silent, relying on color change, head-bobbing, and chemical signaling instead of sound. Among archosaurs, crocodilians are quite vocal, and birds are famously so, but this does not guarantee that every species in between was a noisemaker.
Small theropods closely related to the bird lineage present an interesting puzzle. Some of these species may have been developing proto-syrinx structures or experimenting with vocal innovations that left no fossil trace. The gap between the larynx-based system of most dinosaurs and the syrinx-based system of modern birds had to be bridged somewhere, and small feathered theropods from the Late Cretaceous are the most likely candidates. Whether those transitional forms could produce anything resembling birdsong, or whether they were stuck in an acoustic no-man’s-land between crocodilian rumbles and avian melodies, is genuinely unknown. It is one of the more tantalizing open questions in paleoacoustics, and one that a single well-preserved fossil throat could potentially resolve.