Sauropods May Have Had Remarkable Beak-Like Mouths

A new study suggests sauropods may have sported tough beak-like coverings around their toothy jaws.

Sauropods were peculiar animals with even more peculiar heads.

Their skulls were tiny for their colossal bodies, built from delicate bones riddled with openings, with huge nasal cavities pushed high and far back toward the eyes. For decades, paleoartists often reconstructed the long-necked dinosaurs’ skulls by simply stretching skin over the bone, a habit known as “shrink-wrapping.”

The results looked plausible enough—but something about those faces was probably wrong.

At one point, some paleontologists considered whether some sauropods might have carried elephant-like trunks. It was a pretty wild idea, but after careful analysis of fossils, the hypothesis has since largely fallen apart.

Now another possibility is coming into sharper focus, and it may make sauropods look stranger still.

A new study suggests that Camarasaurus may have had a broad, turtle-like keratinous covering around its jaws—while still retaining a full set of teeth. Researchers led by Giacomo Gobbo call the structure an odontoscutum, or “tooth shield.”

Rather than a smooth reptilian mouth wrapped tightly over the skull, the animal may have had a much more heavily reinforced, beak-like face.

The study appeared as a preprint and has not yet been peer-reviewed. But if the interpretation holds, it adds another piece to a larger rethink of what sauropods actually looked like in life.

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The Chambered Lizard

Camarasaurus lived around 150 million years ago, during the Jurassic period, in what is now the western United States, sharing the Morrison Formation ecosystem with Diplodocus, Apatosaurus, Stegosaurus and Allosaurus. It could reach roughly 15 meters (50 feet) in length. Although enormous by modern standards, it was merely middleweight among sauropods.

Its name means “chambered lizard,” a reference to the large hollow spaces inside its vertebrae. Its air-filled cavities helped lighten the skeleton without sacrificing too much strength—a trademark sauropod feature. Paleontologist Edward Drinker Cope coined the name in 1877 after examining the distinctive vertebrae.

Its head made it stand out. Where Diplodocus had a long, low skull and slender peg-like teeth, Camarasaurus had a short, tall, almost boxy head armed with stout, spoon-shaped teeth capable of handling tougher vegetation.

Its skull was also built around large openings for the eyes, airways, and jaw muscles. Like other sauropod skulls, the thin, hollow bones were easily crushed after death, which makes good fossil specimens unusually valuable.

But it was the same skull openings that gave paleoartists trying to reconstruct what the dinosaur looked like a lot of headaches. Skin does not simply sink into every fenestra, or skull window. Nostrils, muscles, gums, and other tissues can profoundly alter the outline of a living head, and such tissue never fossilizes. Paleontologist and paleoartist Mark Witton has illustrated this problem with Europasaurus, showing how the same sauropod skull can produce radically different faces depending on how much tissue is restored.

Reading a face from tiny holes in bone

To arrive at least a plausible rendition of a sauropod face, Gobbo and his colleagues looked at the rostral neurovascular system. This network of nerves and blood vessels supplies the front of the face. Of course, the structures disappear after death, but the small holes and grooves through which they passed remain in the bone.

The researchers examined more than 300 living reptiles and birds. Lizards provided a model for fleshy lips, crocodilians for exposed teeth, and birds and turtles for different varieties of keratinous beaks. They then compared those patterns with an exceptionally preserved Camarasaurus skull and two other sauropods, Galeamopus and Kaatedocus.

On the team’s scatter plots, all three sauropods clustered largely with birds, the reference group for a keratinous covering. A separate seven-trait assessment of Camarasaurus likewise pointed toward heavily keratinized tissue, although not something identical to a modern bird beak.

And this was emphatically not a parrot bill pasted onto a sauropod. The authors reconstruct the odontoscutum as a broad keratinous covering along the outside of the upper and lower jaws. The tips of the teeth remained exposed, while the harder tissue surrounded and supported their bases. Their life reconstruction gives Camarasaurus a fuller, reinforced mouth quite unlike the familiar skull-hugging versions.

Not every statistical analysis produced a neat bird match, and the fossil comparison included only three sauropods. The authors explicitly describe their principal-component analysis as preliminary and warn that the tiny fossil sample can exaggerate differences between groups.

So All Sauropods Had “Beaks”?

The idea of beaked sauropods is itself not new. In a 2016 study of this same exceptionally preserved Camarasaurus specimen, Kayleigh Wiersma and Martin Sander found teeth whose roots extended unusually far from their sockets without showing the wear expected if they had simply been exposed. They proposed that tough gingival tissue, perhaps accompanied by keratin, covered and stabilized them.

Moreover, sauropod teeth sometimes fossilize in intact rows after the surrounding jaw bone has disappeared.

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“There must have been something holding them in place,” Wiersma told Science in 2019. “Otherwise they would have been scattered all around the dig site.”

The case has continued to build. A 2024 study of the dwarf sauropod Europasaurus reported comparable tooth anatomy and argued that strong connective tissue probably partially covered and stabilized the dentition. The researchers suggested that this structure might even have been related to the keratinous rhamphotheca found in living birds and turtles.

The new work tries to test the same idea independently, using the anatomy of nerves and blood vessels rather than teeth alone. Its authors go further, proposing that some form of keratinized mouth covering may have been widespread, perhaps even ancestral, among sauropodomorphs.

That claim will require many more skulls and paintaking analysis of nerve tissue. But it illustrates how dramatically a dinosaur can change once paleontologists stop treating bone as the boundary of the living animal.

We have known the skeletons of sauropods for nearly two centuries. But only now are their faces coming into focus.

The study is available as a preprint on ARPHA Preprints.