The Pliosaurs ("more lizards") were marine reptiles from the Jurassic and Cretaceous Periods. They originally included members of the family Pliosauridae, of the Order Plesiosauria, but several other genera and families are now also included; the number and details of which vary according to the classification used. The name is derived from Greek: πλειων meaning 'more/a higher degree' and σαυρος meaning 'lizard'. The pliosaurs, along with their relatives, the true plesiosaurs, and other members of Sauropterygia, were not dinosaurs.
The group was characterised by having a short neck and an elongated head, in contrast to the long-necked plesiosaurs. They were carnivorous and their long and powerful jaws carried many sharp, conical teeth. Pliosaurs range from 4 to 15 meters in length. Their prey may have included fish, ichthyosaurs and other plesiosaurs.
Pliosaurs almost entirely disapeared by the mid-Cretaceous. They were replaced by the mosasaurs.
Typical genera include Macroplata, Kronosaurus, Liopleurodon, Pliosaurus and Peloneustes. Fossil specimens have been found in England, Mexico, South America, Australia and the Arctic region near Norway.
Many very early (from the Rhaetian (Latest Triassic) and Early Jurassic) primitive pliosaurs were very like plesiosaurs in appearance and indeed used to be included in the family Plesiosauridae.
The taxonomy presented here is mainly based on the plesiosaur cladistic analysis proposed by O'Keefe in 2001 and Smith & Dyke in 2008.
- Suborder: †Pliosauroidea Welles, 1943 sensu O'Keefe, 2001
- ? †Bishanopliosaurus Dong, 1980
- †Hauffiosaurus O’Keefe, 2001
- ? †Megalneusaurus Knight, 1898
- ? †Pachycostasaurus Cruickshank, Martill & Noe, 1996
- ? †Sinopliosaurus Young, 1942
- †Thalassiodracon Storrs & Taylor, 1996
- Family: †Rhomaleosauridae (Nopsca, 1928) Kuhn, 1961 sensu Smith & Dyke, 2008
- Family: †Leptocleididae White, 1940 sensu Smith & Dyke, 2008
- Family: †Pliosauridae Seeley, 1874 sensu Smith & Dyke, 2008