Mosasaur
Mosasaurs are an extinct group of large marine reptiles containing 38 genera in total.Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764.
Mosasaurs probably evolved from an extinct group of aquatic lizards[1] known as aigialosaurs in the Early Cretaceous.
During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators.
They became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago.