A new species of massive marine reptile, Tylosaurus rex, has been described from fossils unearthed in northern Texas. The 43-foot-long mosasaur lived about 80 million years ago and ranks among the largest of its kind. Researchers published the findings on May 21, 2026.
The discovery was led by scientists at the American Museum of Natural History, the Perot Museum of Nature and Science in Dallas, and Southern Methodist University. Lead author Amelia Zietlow said the fossils had initially been misidentified as another species before detailed comparisons revealed distinct traits, including larger size and finely serrated teeth. The holotype specimen, found in 1979 near a reservoir outside Dallas, is now on display at the Perot Museum.