The mighty mosasaurs were once thought to have ruled only the oceans — but a new discovery is rewriting that story. In North Dakota, scientists have uncovered a massive tooth lodged in the sediments ...

The tooth was found in 2022 within river sediments of North Dakota’s Hell Creek Formation, a site well known for yielding dinosaur fossils such as Tyrannosaurus rex and Edmontosaurus. The discovery of ...

Large marine reptiles that dominated the seas might have inhabited river systems during their final years, according to recent studies indicating that certain mosasaurs evolved to thrive in freshwater ...

This video explores how Mosasaurus evolved into a marine predator so dominant that it effectively “broke the game” of prehistoric ocean life. Scientists highlight the creature’s immense size, ...

A massive predator’s tooth turned up in North Dakota, a place better known for dinosaurs than sea monsters. The discovery raised eyebrows right away. Mosasaur fossils usually come from ocean sediments ...

Giant mosasaurs, once thought to be strictly ocean-dwelling predators, may have spent their final chapter prowling freshwater rivers alongside dinosaurs and crocodiles. A massive tooth found in North ...

Giant ancient sea reptiles, called mosasaurs, lived in rivers as well as seas, according to a new study. The research was based on the fossil of a tooth that was previously found in the United States.