Pliosauroidea is an extinct clade of plesiosaurs, known from the earliest Jurassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled pleisiosaurs in possessing relatively long necks and smaller heads. They originally included only 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 distinguishing characteristics are a short neck and an elongated head, with larger hind flippers compared to the fore flippers, the opposite of the plesiosaurs. They were carnivorous and their long and powerful jaws carried many sharp, conical teeth. Pliosaurs range from 4 to 15 metres and more in length. Their prey may have included fish, sharks, ichthyosaurs, dinosaurs and other plesiosaurs. The largest known species are Kronosaurus and Pliosaurus macromerus; other well known genera include Rhomaleosaurus, Peloneustes, and Macroplata. Fossil specimens have been found in Africa, Australia, China, Europe, North America and South America. Many very early (from the Early Jurassic and possibly Latest Triassic, i.e. Rhaetian) primitive pliosauroids were very like plesiosauroids in appearance and, indeed, used to be included in the family Plesiosauridae. Name Pliosauroidea was named by Welles in 1943. It is adapted from the name of the genus Pliosaurus, which is derived from the Greek (), meaning "more/closely", and () meaning "lizard"; it therefore means "more saurian". The name Pliosaurus was coined in 1841 by Richard Owen, who believed that it represented a link between plesiosauroids and crocodilians (considered a type of "saurian"), particularly due to their crocodile-like teeth. Classification Taxonomy The taxonomy presented here is mainly based on the plesiosaur cladistic analysis proposed by Hilary F. Ketchum and Roger B. J. Benson, 2011 unless otherwise noted. Suborder Pliosauroidea ? Eurysaurus ? Sinopliosaurus Family Rhomaleosauridae Archaeonectrus Borealonectes ? Bishanopliosaurus Eurycleidus Macroplata Maresaurus Rhomaleosaurus Meyerasaurus Sthenarosaurus ? Yuzhoupliosaurus Family Pliosauridae Anguanax Attenborosaurus Gallardosaurus Hauffiosaurus Marmornectes Megalneusaurus Liopleurodon Eardasaurus Pachycostasaurus Peloneustes Pliosaurus Rhaeticosaurus Simolestes Thalassiodracon Subfamily Brachaucheninae Brachauchenius Kronosaurus Makhaira Megacephalosaurus Polyptychodon Sachicasaurus Monquirasaurus Stenorhynchosaurus Luskhan Phylogeny Pliosauroidea is a stem-based taxon that was defined by Welles as "all taxa more closely related to Pliosaurus brachydeirus than to Plesiosaurus dolichodeirus". Pliosauridae and Rhomaleosauridae are stem-based taxa too. Pliosauridae is defined as "all taxa more closely related to Pliosaurus