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.
Mierasaurus
Asides from "Mierasaurus" and "Moabosaurus", all other turiasaurs are Jurassic in age, and turiasaurs had previously been considered to have gone extinct at the Jurassic-Cretaceous boundary. However, turiasaurs are not known from the Jurassic-aged (more specifically, dating to the Tithonian epoch) deposits of the Morrison Formation, or from any other equivalent deposits in western (Laramidian) North America. This means that they may have reached North America at some point after the Tithonian, although the possibility that they were present but have not been found cannot be excluded. It is also possible that they were present in eastern (Appalachian) North America in the Late Jurassic, and spread to Laramidian North America subsequently. However, the presence of "Mierasaurus" in Valanginian deposits correlates with a substantial drop in sea level that occurred during the epoch, which may have formed a land bridge and allowed turiasaurs - and potentially other groups, such as haramiyidan mammals - to spread from Europe to North America.