A new mosasaur species found in Texas suggests that some ancient ocean predators were bigger and more powerful than previously thought. This discovery comes from bite marks, broken jaws, and a huge skull.
This animal was not a dinosaur, but it lived at the same time and likely dominated its part of the ocean.
Discovering a New King of the Sea
Scientists from the American Museum of Natural History, the Perot Museum of Nature and Science, and Southern Methodist University identified this new mosasaur. They named it Tylosaurus rex, or T. rex, which means "king of the tylosaurs."
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Start Your News DetoxThis predator was one of the largest mosasaurs known, reaching up to 43 feet long. Its fossils are about 80 million years old. They were found mainly in northern Texas, in rocks from a shallow seaway that once covered much of central North America.
Amelia Zietlow, the lead author of the study, noted that "Everything is bigger in Texas and that includes the mosasaurs, apparently." The study was published in the Bulletin of the American Museum of Natural History.
How a Misidentified Fossil Led to a New Species
Zietlow, a research associate at the American Museum of Natural History, started this project during her Ph.D. studies. She found a mosasaur fossil in the museum's collection that seemed to be wrongly identified as Tylosaurus proriger.
Zietlow and her team compared this fossil with the original T. proriger specimen, which was described over 150 years ago. They realized the American Museum of Natural History fossil, along with more than a dozen others, belonged to a different species.
These newly identified fossils were larger than T. proriger and had finely serrated teeth, which is rare for mosasaurs. Most T. proriger fossils are about 84 million years old and come from Kansas. The new fossils are mostly from Texas and are about 4 million years younger.
Honoring Past Discoveries and Uncovering Aggression
The name T. rex also honors paleontologist John Thurmond. In the late 1960s, he noticed that tylosaurs from northeast Texas were unusually large and might be a new species. He informally called them "Tylosaurus thalassotyrannus," or "sea tyrant."
The main specimen for the new T. rex is a huge fossil displayed at the Perot Museum. It was found in 1979 near Dallas. Besides its impressive size, from 25 to 43 feet long, T. rex had strong jaw and neck muscles. This suggests it was a powerful predator.
Ron Tykoski, a study co-author and curator at the Perot Museum, said T. rex was "roughly twice the length of the largest great white sharks." He added that it seemed "a much meaner animal than other mosasaurs." The study found evidence of violence within this species not seen before in other Tylosaurus specimens.
One fossil, nicknamed "The Black Knight," shows signs of this aggression. It's missing the tip of its snout and has a broken lower jaw. Researchers believe these injuries could only have been caused by another T. rex.
Several well-known mosasaur fossils, once called T. proriger, will now be reclassified as T. rex. These include "Bunker" at the University of Kansas and "Sophie" at the Yale Peabody Museum.
Reshaping Mosasaur Evolution
This study also addresses a big challenge in mosasaur research. For nearly 30 years, scientists have used mostly the same data to study how mosasaurs evolved.
For the T. rex study, the team created a completely new dataset. They proposed a new way to understand how tylosaurs are related. These findings suggest that mosasaur evolution needs to be re-examined, as many older studies relied on outdated information.
Zietlow noted that this discovery "highlights the need to revisit long-standing assumptions about mosasaur evolution." She added that it's time "to modernize the tools we use to study these iconic marine reptiles."
Co-author Michael Polcyn from Southern Methodist University said these findings change how we see mosasaurs, both physically and evolutionarily. He emphasized that Texas is a key area for understanding ancient marine ecosystems. This discovery also signals a new era for studying these powerful predators.
Deep Dive & References
A gigantic new species of Tylosaurus (Squamata, Mosasauridae) from Texas : and a revised character list for phylogenetic analyses of Mosasauridae - Bulletin of the American Museum of Natural History, 2026
