Tylosaurus rex: The New “Sea Lizard King” from Texas – Largest Mosasaur Ever Recorded!

Paleontologists have announced the discovery of Tylosaurus rex, a gargantuan new species of mosasaur unearthed in North Texas that officially claims the тιтle of the largest marine reptile of its kind ever found. Described in the Journal of Systematic Palaeontology (June 2026), this “Sea Lizard King” lived approximately 75 million years ago, ruling the Western Interior Seaway with undisputed ferocity.

The holotype specimen—a mᴀssive 1.8-meter skull and a near-complete skeleton—was recovered from the Ozan Formation in Fannin County. Extrapolating from the skull and vertebral column, scientists estimate the creature reached a staggering 16–17 meters (52–56 feet) in length. This surpᴀsses the famous Tylosaurus proriger and rivals the size of the largest predatory whales.

What distinguishes T. rex (the mosasaur, not the dinosaur) is its hyper-robust skull and specialized denтιтion. Unlike the slender snouts of its relatives, this predator possessed a mᴀssive, wide rostrum and interlocking, serrated teeth designed for “grip-and-tear” feeding on large prey, including other mosasaurs, giant sea turtles, and plesiosaurs. “This wasn’t just a bigger Tylosaurus; it was a specialized macropredator evolved to sit at the absolute top of the food chain,” says lead researcher Dr. Thomas Rivera.

The discovery proves that Texas was a primary hub for Late Cretaceous marine biodiversity. Its immense size suggests a high-calorie diet and perhaps a more aggressive metabolism than previously thought for cold-blooded reptiles. As CT scans of the braincase continue, Tylosaurus rex is set to redefine our understanding of how these prehistoric sea monsters achieved global dominance. The king of the land now has a namesake rival in the deep.