Since the 1930s, dinosaurs have rumbled, snarled and roared on film. But the fossilized inspirations for these cinematic characters have preserved little evidence for any such dramatic voices.
In a paper published last week in the journal PeerJ, researchers announced the discovery of a fossilized herbivorous dinosaur from China preserving a surprisingly birdlike throat. It provides a clue that the origins of birdsong might go as far back as the beginning of dinosaurs themselves.
The two-foot-long dinosaur, which the researchers named Pulaosaurus, was discovered in 163-million-year-old rocks in northeastern China, said Xing Xu, a paleontologist at the Chinese Academy of Sciences in Beijing and an author of the paper. The largely complete skeleton offers a strong anatomical view into the fleet-footed, beaked animal, an early member of the family that later produced “duck-billed” hadrosaurs and horned dinosaurs.
The Jurassic period formation that produced Pulaosaurus is also the source of other dinosaur discoveries like the feathered proto-bird Anchiornis, the tiny, batlike Yi qi and the feathered herbivorous dinosaur Tianyulong. Unlike those animals, Pulaosaurus is not preserved with obvious soft tissues that could help better explain its living appearance. “On some parts of the fossil we thought we’d found very thin filaments, but we can’t confirm that,” Dr. Xu said.
The team did note interesting formations in the stomach region of the fossil but hasn’t determined what those are. “They could be stomach contents — food eaten by this dinosaur, or organs, or maybe even eggs within the body,” Dr. Xu said.
The most interesting remains were found within the throat. In vertebrates, vocal organs play an important role in protecting the airway and helping produce everything from simple hisses and grunts to speech. In most living reptiles, these tissues are composed of cartilage, and can produce simple bellows, grunts, groans and chirps. Modern birds have vocal organs made up partially of delicate bones, allowing them to make much more complicated sounds — including, in some cases, mimicking human speech.
The anatomy of dinosaur vocal organs has long been a mystery. “Even when you have a dinosaur skeleton preserved, you don’t always have these isolated bones preserved with other skull elements,” Dr. Xu said. “They’re very thin bones, very delicate and hard to preserve.”
The first report of a non-bird dinosaur with fossilized vocal organs — the armored ankylosaur Pinacosaurus, which lived millions of years after Pulaousaurus — arrived only in 2023. While Pinacosaurus lacked the distinct voice box seen in birds, the researchers concluded, its bony larynx was large and mobile enough to possibly help produce birdlike noises. Pulaousaurus seems to have had a similar vocal setup, Dr. Xu said, albeit one that was less developed.
Pulaousaurus and Pinacosaurus belong to dinosaur families separated from each other by millenniums of evolution. Each is also distant from the lineage that produced modern birds. While it’s possible that they evolved independently in different lineages, Dr. Xu said, the presence of similar vocal organs in distinct groups suggests that birdlike vocals might have emerged with dinosaurs’ earliest ancestors, over 230 million years ago.
For now, the more complex vocal machinery found in everything from parrots to penguins — specifically their voice box, the syrinx — remains unknown in non-bird dinosaurs. But they might turn up one day in a well-preserved fossil, Dr. Xu said. It’s even possible that they already have and were simply misidentified, as the tiny, delicate bones are easy to miss.
“We hope that in the future we can find more specialized structures relating to sound so we can do research on how dinosaurs produced their voices,” Dr. Xu said.
So what did Pulaousaurus sound like? Did it twitter, squeak, or chirp like a baby crocodile?
“We don’t know,” Dr. Xu said. “It could be some strange noise. It’s hard to predict.”
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