Scientists from the American Museum of Natural History and the Perot Museum have identified a massive new species of mosasaur, Tylosaurus rex, from 80-million-year-old fossils in North Texas. Measuring up to 43 feet long, this apex marine predator was significantly larger and more aggressive than previously documented species within its lineage.
Uncovering a hidden species in museum collections
For decades, a massive prehistoric predator sat largely unnoticed, mislabeled within museum archives. The discovery of Tylosaurus rex came after Amelia Zietlow, lead author of the study, noticed that a specific fossil in the American Museum of Natural History collection had been incorrectly identified as Tylosaurus proriger.
By comparing the specimen with the original T. proriger fossil held at Harvard University’s Museum of Comparative Zoology, researchers realized they were looking at an entirely different animal. According to ScienceDaily, the research team identified that these Texas fossils represented a distinct species characterized by its immense size and unique dental structure.
The differences between the two species are stark. While T. proriger fossils are typically found in Kansas and date back roughly 84 million years, the newly named T. rex lived approximately 80 million years ago in the waters of what is now northern Texas. Furthermore, the new species grew to a staggering 43 feet, making it roughly 13 feet longer than its predecessor.
Physical adaptations of a marine titan
The anatomy of Tylosaurus rex suggests a predator built for high-impact hunting. Unlike other mosasaurs, this species possessed finely serrated teeth, a trait rarely seen in its relatives. These teeth, combined with specialized adaptations in the jaw and neck muscles, allowed the reptile to dominate the Cretaceous oceans.
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As the New York Post reported, this aquatic nightmare functioned as the top predator of its ecosystem, much like the terrestrial Tyrannosaurus rex did on land. The sheer scale of the animal—reaching 13.2 meters in length—places it among the largest mosasaurs ever recorded.
Evidence of violent intraspecies combat
The fossil record for T. rex does more than just reveal its size; it reveals a history of aggression. Researchers found physical evidence of combat within the species, suggesting that these giants frequently engaged in brutal battles with one another.
One specimen currently housed at the Perot Museum in Dallas exhibits a broken jaw and is missing the tip of its nose. Paleontologists believe these are not accidental injuries but rather "war wounds" sustained during fights with rivals.
As ScienceAlert noted, the examination of well-preserved fossils across the north Texas region has provided a level of insight into species-specific violence that had not been seen in other Tylosaurus specimens.
The Texas-sized legacy of the sea tyrant
The name Tylosaurus rex serves as a tribute to both the famous land predator and the work of paleontologist John Thurmond. In the late 1960s, Thurmond recognized that these massive specimens from northeast Texas were unique, informally calling them Tylosaurus thalassotyrannus, or "sea tyrant."
The primary holotype specimen for this species was originally discovered in 1979 near an artificial reservoir outside of Dallas. According to Audacy, the fossils were recovered near Lake Ray Hubbard and are now a centerpiece of the Perot Museum’s collection.
The discovery underscores the importance of re-examining existing museum collections. By looking closer at specimens that were previously thought to be well-understood, scientists are finding that the prehistoric world was far more complex—and much more violent—than they once believed.
