80 million-year-old sea monster fossil reveals mushroom-like shell-crushing teeth

Two jaw fragments from Globidens alabamaensis —a rare species of mosasaur with unique blunt teeth—have been discovered in Texas.

These findings shed light on the feeding habits of this 20-foot-long marine predator.

These fossils, preserved from the Late Cretaceous period, reveal how the species thrived by crushing shelled prey. This adaptation differentiated it from other large marine predators of its time.

Discovery of rare fossil fragments in Texas

In 2023, a private fossil hunter uncovered two jaw fragments belonging to Globidens alabamaensis in northeastern Texas, specifically in the Ozan Formation. This discovery has excited researchers due to the rarity of such finds. The fossils date back to the Campanian Age, around 83.6 to 72.1 million years ago.

One of the jaws still holds 12 teeth, while the other has six remaining. The rounded, blunt teeth are an inch long and designed for crushing hard-shelled prey.

“These structures with their mushroom shape are great for impact attacks—for shell crushing,” explained Bethany Burke Franklin , a marine paleontologist and educator at the Texas Through Time fossil museum, in an interview with LiveScience . Although she was not directly involved in the study.

According to Franklin, the unique teeth enabled the mosasaur to capture and kill its prey through cracking shells, which was something that made Globidens distinctly different from other mosasaurs whose teeth were sharp and pointy, like a dagger.

What makes this discovery even more significant is the fact that G. alabamaensis was first identified in 1912, but only a few near-complete specimens have ever been found. Most fossils consist of teeth or small jaw fragments.

The mosasaur’s adaptation to shell-crushing

Unlike most mosasaurs, which evolved sharp teeth for catching and devouring fish and other marine animals, Globidens alabamaensis had blunt, globular teeth. This adaptation made it possible to overcome the thick shells of turtles, ammonites and bivalves.

This species inhabited the Western Interior Seaway during the Late Cretaceous period, a water channel that separated North America. It can be hypothesized that due to the large amounts of shelled prey in this seaway, the teeth of Globidens evolved as they did.

According to Franklin, the mosasaurs of that era were rapidly evolving to fill various ecological niches left by other marine predators like ichthyosaurs and plesiosaurs, which had declined due to climate change and ecosystem shifts.

“Multiple species could coexist because they were not taking up the same resources,” said Franklin. This allowed mosasaurs like Globidens to thrive by specializing in shell-crushing, while other species focused on different prey.

The existence of these fossilized jaws suggest that Globidens was well suited for its environment and could capitalize on a food source that other predators may have ignored. This let the species share its habitat with other large mosasaurs that hunted soft-bodied organisms and helped to maintain the balance between the species in the marine environment.

Evolutionary significance of the discovery

The Late Cretaceous was a period of significant evolutionary change for marine reptiles, and mosasaurs emerged as dominant predators in the world’s oceans. Mosasaurs, including Globidens alabamaensis , took over ecological roles left behind by other marine predators that had vanished due to shifting climates and environments. With the Western Interior Seaway teeming with prey, these reptiles diversified rapidly.

Franklin explained that the unique adaptation of Globidens ’ teeth was likely influenced by an “overabundance of cephalopods” in the region. These marine reptiles played an essential role in balancing the food web by filling the niches left vacant by other large predators.

“They were some of the most rapidly evolving predators of the time,” Franklin added, noting how their specialized teeth allowed them to crush shells and feed on creatures other mosasaurs could not.

Despite the abundance of fossil evidence for mosasaurs in general, finds related to Globidens alabamaensis are rare. This makes the Texas discovery especially exciting for paleontologists. The preservation of cranial material, such as the mosasaur’s jaw, is uncommon, as Franklin noted, “Cranial material tends to get squashed more, especially in these thinner strata.”Trevor H. Rempert

The research was published in the Journal of Paleontological Sciences .