Rare Jaw Fossils Discovered in Texas Shed Light on a 20-Foot-Long Mosasaur

Roughly 80 million years ago, a large sea monster swam across present-day Texas. With that land submerged beneath an interior seaway, the predator roamed the waters in search of mollusks, turtles and other shelled creatures to crush with its globular teeth.

That creature, called Globidens alabamaensis, is now extinct. But recently discovered fossilized remains are offering new insights into the beast’s lifestyle and habits, according to a paper recently published in the Journal of Paleontological Sciences.

Researchers first described G. alabamaensis in 1912. Since then, however, very few fossils belonging to the species have been found, leaving scientists mostly in the dark about the mysterious creature.

But last year, a private fossil hunter named Courtney Travanini made a rare find in northeastern Texas: jaw fragments from an adult G. alabamaensis, with teeth still attached.

Travanini discovered the elusive fossils in the North Sulphur River channel near the town of Ladonia, Texas. They were embedded in the Ozan Formation, in an eight-inch-thick deposit that preserves fossils from the Campanian Age, which lasted from 83.6 million to 72.1 million years ago. Travanini loaned the two jaw fragments to a team of researchers who studied the fossils for clues about the life of G. alabamaensis.

The creature had “robust and massive” jaw bones equipped with sturdy, rounded teeth, they write in the paper. Some of the teeth measured about an inch long. The entire animal, meanwhile, could grow to be up to 20 feet long and likely used its chompers to crush the shells of mollusks, turtles and other marine creatures. The fossils also suggest that G. alabamaensis lost and replaced its teeth throughout its lifetime, similar to today’s sharks, reports Live Science’s Richard Pallardy.

G. alabamaensis was a type of mosasaur, a group of large, extinct aquatic reptiles that prowled around during the Late Cretaceous period, between 100.5 million and 66 million years ago. As the climate shifted and other marine predators began to falter, mosasaurs adapted and flourished. With their sleek bodies, long tails and paddle-like limbs, they became the top predators of the shallow seas.

Some mosasaur species evolved sharp, serrated teeth that helped them saw through their prey’s flesh, while others—such as G. alabamaensis—developed rounded, mushroom-shaped teeth that were better suited for crushing. These unique tooth types allowed different mosasaurs to thrive at the same time.

G. alabamaensis, for example, was probably taking advantage of an “overabundance of cephalopods,” says Bethany Burke Franklin, a marine paleontologist with the Texas Through Time fossil museum who was not involved with the research, to Live Science.

“Multiple species could coexist, because they were not taking up the same resources,” she adds.

Mosasaurs went extinct at the same time as the dinosaurs, similarly killed off by the ecological effects of a large asteroid colliding with Earth around 66 million years ago.

Globidens mosasaurs are some of the rarest in North America, known largely from isolated teeth and preserved fragments of jaws. Along with G. alabamaensis, only four other known species make up the genus. But while very few fossils from these creatures have been unearthed, fossils from other types of mosasaurs are more common.

In 2022, for instance, fossil hunter Stephen Kruse found a mosasaur spine, skull and lower jawbones sticking out of a dry creek bed near the North Sulphur River—the same waterway where the G. alabamaensis jaw fragments were recently discovered.

When mosasaurs were still alive, northeastern Texas was submerged under “beautiful, warm, almost tropical oceans and seas filled with fish and reptiles and clams and oysters and sea life,” Ron Tykoski, who helped excavate Kruse’s finds and serves as curator of vertebrate paleontology at the Perot Museum of Nature and Science in Dallas, told FOX4 in 2022.

“It was a wonderful place to live if you were a big, hungry, predatory reptile,” he added.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.