Cretaceous plesiosaurs

Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxon was initially erected in 1869 by Edward Drinker Cope to include the type genus Elasmosaurus with the related Cimoliasaurus, although he did not argue in detail why. Over the following years, many authors recognized this classification on the basis of predominantly postcranial features, becoming one of the three groups in which plesiosaurs were often clas

left|thumb|Life restoration of Muraenosaurus Cryptoclididae is a family of medium-sized plesiosaurs that existed from the Middle Jurassic to the Early Cretaceous. They had long necks, broad and short skulls and densely packed teeth. They fed on small soft-bodied preys such as small fish and crustaceans. The earliest members of the family appeared during the early Bajocian, and they represented the dominant group of long-necked plesiosaurs during the latter half of the Jurassic.

Polycotylidae is a family of plesiosaurs from the Cretaceous. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. Several species survived into the final stage of the Cretaceous, the Maastrichtian around . The possible latest surviving member Rarosaurus from the late Maastrichtian is more likely a crocodylomorph.

Discosaurus is an extinct genus of plesiosaur from the Santonian of Alabama and Mississippi. One species is known, which is D. vestutus.

species of reptile (fossil)

Piratosaurus (meaning "pirate lizard") is a dubious genus of plesiosaur possibly belonging to the Polycotylidae that is known exclusively from the type species P. plicatus, named and described by Joseph Leidy in 1865. It is known only from the holotype, USNM V 1000, a tooth, discovered in Late Cretaceous-aged rocks in the Red River basin of Manitoba; at least one researcher erroneously assumed it was found in Minnesota.