Plotosaurus
Plotosaurus ("swimmer lizard") is an extinct genus of large mosasaurs which lived during the Upper Cretaceous (Maastrichtian) in what is now North America. The taxon was initially described by Berkeley paleontologist Charles Lewis Camp in 1942 from several more or less complete fossil specimens discovered in California, USA. Originally named as Kolposaurus (meaning "bay lizard"), it was changed to Plotosaurus in 1951 when Camp discovered that the name had already been assigned to a type of nothosaur.