What are the sounds of dinosaurs?

In the next generation of dinosaur-based blockbusters, some star creatures may look more like a bird and a little less like a roaring lion.

At least that’s a possibility raised by new research Posted this monthalthough very little is really understood about the singing of dinosaurs.

But a research team has extracted clues about the sounds the extinct creatures could make from what may be the first known fossilized larynx of a dinosaur. It comes from an ankylosaur, a group of armored plant-eaters that were not closely related to birds. This squat, spiny dinosaur (Pinacosaurus grangeri) was discovered in 2005 in Mongolia.

Junkie Yoshida, a paleontologist at the Fukushima Museum in Japan, said the discovery was surprising because the parts of the body involved in vocalization, including the larynx, which are often made of cartilage but can be bony in some animals, were not considered good candidates. for preservation as fossils. (In some animals, the larynx is located near the top of the trachea and contains the vocal cords.)

To try to derive what a dinosaur sounds like to have uttered, Dr. Yoshida’s team also looked at the evolutionary relatives of those Cretaceous creatures, including birds and the dinosaur’s closest relatives – crocodiles.

“They kind of bracket the range of sounds that we might expect,” said Victoria Arbour, a paleontologist at the Royal BC Museum in Victoria, Canada, who was not involved in the new study.

The crocodile’s vocal repertoire includes deep rattling and hissing. “Assuming that dinosaurs made crocodile-like sounds is completely safe,” she said. “That’s the basic anatomy that they’re going to work with. The birds then developed these additional ways of producing sounds where they could modulate the sounds coming out of their throats in a more subtle way.”

Birds and reptiles have very different ways of producing sounds using the organs that surround the bronchi and lungs. In extinct and living relatives of the crocodile, the larynx produces sound. Birds have a different organ, called the syrinx, which is located near their lungs to produce sound. They also have another organ, located near their mouth, to alter those sounds, which allows some birds to create elaborate songs.

Dr. Yoshida and his colleagues determined the size of two parts of the larynx, which would have supported the muscles involved in opening the airway and changing its shape. In ankylosaur, both parts were bone. The team compared their proportions to the throats of dozens of birds and reptiles, including crocodiles, geckos and turtles.

One of the segments that make up the base of Ankylosaurus’ larynx was quite large compared to those of other animals, said Dr. Yoshida, indicating that this dinosaur could open its airways wide to make loud calls that could be heard far away. He added that the other part of the larynx, a relatively long pair of bones, could allow the trachea to change shape to modulate sounds. Perhaps this allowed ankylosaurs To pronounce in a manner similar to birdsthe researchers reported recently in the journal Communications Biology.

Dr. Arbour said that people might assume that sounding like birds means these dinosaurs chirped like meadowsweet. Maybe that’s not true, but “they probably had a wider range of vocalizations than we would give credit to Ankylosaurus otherwise,” she said.

“There are still chances that they made chirping and cooing sounds,” said Dr. Yoshida. But he cautioned that it is too early to understand the specific sounds that dinosaurs may have made. Even one species of bird makes a wide range of sounds, he said, and there are other organs at play, from the mouth and nose to perhaps the syrinx tube.

University of Texas at Austin paleontologist Julia Clarke, who was not part of the study, found the analysis interesting. But she said the way the parts of the larynx and other adjacent bones were arranged in Ankylosaurus was not similar to that of birds.

“Only in pterosaurs do we see something like the condition of birds,” she said.

It’s not clear how the structures the team analyzed would allow Ankylosaurus to change sounds, Dr. Clark said. Throat birds are not used for this. They have an organ called a laryngeal basket that moves up or down to modulate their calls. The larynx appears in all tetrapods – a group that includes animals such as birds, reptiles and mammals that are descended from four-limbed creatures. The anatomy described in the paper differs in different animals whether they can vocalize or not. “We don’t know what any of that difference means,” she said.

She said the parts of the larynx under study probably had more to do with keeping food out of the airway because they helped open and close it. And the layout of the related structures in this Ankylosaurus appears to be very different from that of many other dinosaurs that Dr. Clarke has studied and that appear in the literature.

Could other dinosaurs look like birds? maybe. Dr Clarke and her colleagues found a fossilized syrinx from… About 67 million years ago in an old bird. Since that was before the dinosaurs became extinct, it raises the possibility that some dinosaurs may have had them. But until now, no one has found a fossilized syrinx in a non-avian dinosaur.

She said those parts of the larynx in the new study probably had something to do with the unique features of this ankylosaurus rather than something that could be generalized across dinosaurs. “There are still a lot of questions about the evolution of dinosaur vocalization.”

“Ankylosaurs are strange,” said Dr. Clark. “This is the main message.”