Researchers from the University of Bath in the United Kingdom have uncovered the fossil of a new mosasaur species that ruled the seas during the Cretaceous period. The ferocious marine lizard was an apex predator that thrived in the waters near Morocco at the same time T. rex was on land. The scientist named the creature Thalassotitan atrox (T. atrox) from the Greek words "Thalassa" and "titan," meaning "sea giant." The species name atrox translates to "cruel" or "merciless."