Walking with Dinosaurs, which depicted it as an enormous long and predator; this was based on very fragmentary remains, and considered to be an exaggeration for Liopleurodon, with the calculations of specimens generally considered dubious. Estimating the size of pliosaurs is difficult because not much is known of their postcranial anatomy. The palaeontologist L. B. Tarlo suggested that their total body length can be estimated from the length of their skull which he claimed was typically one-seventh of the former measurement, applying this ratio to L. ferox suggests that the largest known specimen was a little over while a more typical size range would be from . The body mass has been estimated at for the lengths respectively based on the specimen NHM R2680. Additional Kronosaurus specimens and a skeleton of L. ferox, GPIT 1754/2, show that their skulls were actually about one-fifth of their total body length. One specimen, CAMSMJ.27424, has an estimated total length of . The largest known skull, NHM R3536, about long would have belonged to an individual measuring approximately long and weighing . Classification Liopleurodon belongs to clade Thalassophonea, a short necked clade within the Pliosauridae, a family of plesiosaurs, thalassophoneans ranged from the Middle Jurassic to early Late Cretaceous, and have been found worldwide. Liopleurodon was one of the basal taxa from the Middle Jurassic. Differences between these taxa and their relatives from the Upper Jurassic include alveoli count, smaller skull and smaller body size. An analysis in 2013 classifies Liopleurodon, Simolestes, Peloneustes, Pliosaurus, Gallardosaurus, and Brachaucheninae as Thalassophonea. The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only. Palaeobiology Four strong paddle-like limbs suggest that Liopleurodon was a powerful swimmer. Its four-flipper mode of propulsion is characteristic of all plesiosaurs. A study involving a swimming robot has demonstrated that although this form of propulsion is not especially efficient, it provides very good acceleration—a desirable trait in an ambush predator. Studies of the skull have shown that it could probably scan the water with its nostrils to ascertain the source of certain smells. A fragmentary specimen possibly belonging to a young adult individual, PETCM R.296, contained numerous hooklets of teuthoid cephalopods, fish bones and a single reptilian tooth in its stomach. Although its exact dietary preference cannot be determined, Martill proposed three suggestions. One possibility is that Liopleurodon could have fed on