New Mosasaur Species Tylosaurus rex Identified from Texas Fossils

Scientists have identified a new species of mosasaur, a giant marine reptile that lived during the Cretaceous period, naming it Tylosaurus rex. The species, described in a study published in the Bulletin of the American Museum of Natural History, reached up to 43 feet in length and possessed finely serrated teeth and powerful jaws, making it one of the most formidable predators of its time. The fossils, approximately 80 million years old, were discovered primarily in northern Texas.

The discovery began when paleontologist Amelia Zietlow, a research associate at the American Museum of Natural History, examined a fossil in the museum’s collection that had been labeled as Tylosaurus proriger, a species first described in 1869. Zietlow noticed that the specimen, found in 1979 near an artificial reservoir outside Dallas, did not match other examples of that species. After comparing it with the original name-bearing fossil of T. proriger at Harvard’s Museum of Comparative Zoology, she and her colleagues determined it belonged to a previously unrecognized species. More than a dozen other fossils at various institutions shared the same traits, leading to their reclassification.