Mosasaur
Mosasaurs (from Latin "Mosa" meaning the 'Meuse river', and Greek σαύρος "sauros" meaning 'lizard') 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 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.
Mosasaurini
The Mosasaurini are a clade of derived mosasaurine mosasaurs. The tribe contains one of the largest known mosasaur species, "Mosasaurus hoffmannii" at over 12 meters in length, but it is notable that such a size is unusual within the tribe and even within the genus "Mosasaurus" itself. Other large mosasaurins are in a size range around 8 meters in length (such as "Plotosaurus", "Eremiasaurus" and "Mosasaurus conodon") whilst others are even smaller in a range of about 5–6 meters in length (such as "Mosasaurus beaugei" and "Mosasaurus missouriensis").