Tylosaurus rex: Ancient Sea Monster as Long as a City Bus

Until now, we have known Tyrannosaurus rex as the unmatched terrestrial predator of the prehistoric era. However, new paleontological discoveries reveal that the ancient seas of Texas 80 million years ago were dominated by a terrifying ‘aquatic twin’ of T. rex: Tylosaurus rex. This newly described marine monster, identified from tens-of-millions-of-years-old fossils, has been dubbed the ‘king of all tylosauruses’ due to its massive size and highly aggressive nature. At the length of a New York city bus, it ranks among the largest mosasaurs ever found on Earth.

‘Everything is bigger in Texas, and it seems the same applies to mosasaurs,’ said Amelia Zietlow, lead author of the study from the History Museum at the Castle in Wisconsin, in a statement cited by IFL Science.

Interestingly, the 80-million-year-old fossil was not newly excavated. It was actually discovered in 1979 near Dallas and stored at the American Museum of Natural History. For years, scientists mistakenly identified it as Tylosaurus proriger, another mosasaur species known for 150 years. The misidentification was corrected after Zietlow conducted a detailed re-examination, uncovering stark physical differences compared to standard T. proriger specimens.

T. proriger is commonly found in Kansas and dates back around 84 million years ago, whereas the new monster’s fossil originates from Texas and is from a younger era, approximately 80 million years ago. Based on strong evidence, scientists have agreed to classify the Texas fossil as a new species. The complete holotype of Tylosaurus rex is now proudly displayed at the Perot Museum of Nature and Science.