Mosasaurs were the first extinct reptiles to be recognized by science and therefore had great importance in the development of natural sciences in the 18th and 19th centuries. The first finds took place in 1764, in the Maastricht region of Holland, hence its name. Meuse is the Latin form of Meuse (or Maas), which refers to the river that crosses this Dutch city. The discovery of this animal was crucial in the development of the theory of biological evolution. In the early 1800s, French naturalist Georges Cuvier used mosasaurs as evidence of species extinction over time – an important aspect of evolutionary theory that would develop more solidly in the second half of the 19th century. Mosasaurs lived exclusively in the Late Cretaceous. , and like other aquatic reptiles, are clearly adapted to the aquatic environment. Despite the name being associated with the Meuse River (the geographic location where the fossils were found), the vast majority of Mosasaurs lived in a marine environment. The skulls of most Mosasaurs were elongated, especially at the front. The teeth were massive and strongly associated with the alveolar bones by periodontal ligaments, bundles of collagen fibers, and a thick cellular cementation. The jaw bones formed an additional movable joint, allowing for greater force in biting and capturing prey. Mosasaur fossils with caudal vertebrae ossified to each other suggest the occurrence of pathologies that affect present-day whales, due to the stress of movement. Mosasaurs could range from 1 to 15 meters in length, depending on the species. They were active predators that inhabited the area of the oceans close to the surface.