Liopleurodon (pronounced /ˌliːoʊˈplʊrədɑn/, meaning 'smooth-sided teeth') is a genus of large, carnivorous marine reptile belonging to the Pliosauroidea, a clade of the short-necked plesiosaurs. Two species of Liopleurodon, L. ferox and L. pachydeirus, lived during the Callovian stage of the Middle Jurassic Period (c. 160 million to 150 million years ago mya), while the third, L. rossicus, lived during the Late Jurassic. It was an apex predator of the Middle to Late Jurassic seas that covered Europe.
The genus name Liopleurodon was coined by H.E Sauvage in 1993 on the basis of very poor remains consisting of three large, 70 mm, teeth. One tooth was found near Boulogne-sur-Mer, France in layers dating from the Callovian was named Liopleurodon ferox, another from Charly, France was named Liopleurodon grossouvrei, while a third discovered near Caen, France was originally described as Poikilopleuron bucklandi and ascribed by Sauvage to the species Liopleurodon bucklandi). Sauvage did not ascribe the genus to any particular group of reptiles in his descriptions.
Liopleurodon fossils have been found mainly in England and France, with one species known from Russia. Fossil specimens referrable to Liopleurodon and contemporary (Callovian) with those from England and France have been found in Germany.
Currently, there are three recognized species within Liopleurodon. L. ferox is well known from finds in the Callovian strata of England and France; while also from the Callovian of England is the rarer L. pachydeirus, described by Seeley as a Pliosaurus (1869). L. rossicus has been found in Russia's Volgian region. The latter species was initially described by Novozhilov (1948) as belonging to Pliosaurus, and is the type species of the genus Strongylokroptaphus. Only L. ferox is known from more or less complete skeletons.
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.
The largest known Liopleurodon skull belongs to L. ferox. It measures 1.5 meters long and was originally estimated (Tarlo, 1960) to belong to an animal about 10.5 meters (34 feet) in length. Later work (Noe, 2004) cast doubt on the model used to estimate the length of Liopleurodon, which had been based on the 1:7 skull length to body length ratio found in the famous (and morphologically similar) Kronosaurus skeleton mounted at Harvard's Museum of Comparative Zoology. Analysis of two mostly complete adult L. Ferox skeletons showed that the ratio of skull length to body length was more in the range of 1:5 or even 1:4, leading Noe to estimate that Tarlos's L. Ferox was only about 7 meters (23 feet), with a corresponding weight of about 2.5 metric tons (2.75 tons).15 (The original reconstruction of Harvard's Kronosaurus Queenslandicus is now known to have included too many vertebrae, resulting in a size estimate of ~ 40 feet as well as derivation of an erroneous skull length to body length ratio. K. Queenslandicus is now believed to have had a skull to body ratio of 1:5 and a corresponding length of about 8 meters.)
A mandible on display in the Oxford University Museum of Natural History, estimated to be over 3 meters (preserved 2.875m) and to have come from a skull perhaps 3.6 meters in length, was at one time classified as Liopleurodon macromerus. (When the mandible was described, it was originally assigned to Stretosaurus (as Stretosaurus macromerus). The genus Stretosaurus later became a junior synonym of Liopleurodon.) However, the Oxford mandible has since been re-classified as Pliosaurus macromerus.
The Liopleurodon ferox depicted in the 1999 BBC television series Walking with Dinosaurs—an enormous 25 meter-long (80 feet) monster weighing up to 150 tons—is not considered to be based on a reasonable estimate of L. ferox's maximum size. In fairness to the program's producers, it should be noted that the 3 meter mandible of the Oxford Pliosaurus macromerus was, at the time of the series, classified as belonging to a Liopleuridon macromerus (it was not re-classified as Pliosaurus macromerus until 2003).
Because fossils are rare (meaning that it is unlikely we would happen to find the largest example of a particular ancient species), and because pliosaurs, like dinosaurs, did not stop growing with age, it is certainly likely that very old individuals of L. ferox grew to a size somewhat exceeding that of the largest known specimen, perhaps to 10 meters (33 feet) and 5-6 metric tons (5.5 - 6.6 tons). This would place L. Ferox in roughly the same size class as modern female Orcas.
Remains excavated from the Kimmeridge Clay Formation of England support the existence of a pliosaur taxon larger than any known Liopleuridon, possibly up to 15 meters (49.2 feet long). However, these remains have not been positively identified as belonging to Liopleurodon.
The discovery of a very large pliosaur was announced in 2002, from Mexico, nicknamed the 'Monster of Aramberri'. A cautious estimate placed this juvenile at about 15 meters (49.2 ft) long. It was widely reported as belonging to Liopleurodon, however no taxonomic conclusions could be made due to poor preservation and fact that the remains were of a partial vertebral column (non-diagnostic). The specimen was dated to the Kimmeridgian age of the La Caja Formation.
In 1999, Liopleurodon was featured in an episode of the 1999 BBC television series Walking with Dinosaurs, where its was claimed to be 25 meters (80 feet) long and up to 150 tons. In the program, a gigantic Liopleurodon was depicted attacking and devouring the theropod dinosaur Eustreptospondylus, before becoming beached during a typhoon and suffocating under its own weight. Two adult Eustreptospondylus (in a twist of irony) who survived the storm feed upon it. The depiction of Liopleurodon leaping onto the land in order to catch land-based prey is entirely speculative, although the program's producers state that the behavior was inspired by that of orcas.
Liopleurodon reappears with the same WWD design and size in a BBC spin-off series called Chased by Sea Monsters, and is shown feeding on a Leedsicthys corpse. It also makes a brief cameo chasing an icthyosaur in another spin-off called Dinosaurs: Giants of Patagonia.
According to a 2008 article written for About.com, the popularity of Liopleurodon, which had previously been more obscure in popular culture than other well-known pliosaurs such as Kronosaurus, experienced an upsurge following its mention in the online animated short Charlie the Unicorn.
A Liopluerodon is the main antagonist in The Land Before Time Journey to the Big Water and along with the Megalodon there are the Sharptooths that are called Swimming Sharptooths or Sharptooth Swimmers.
A pod of Liopluerodons appear in Series 5 of Primeval and attack a submarine that came through an anomaly to the Jurassic.Liopluerodon previously appeared in the second Primeval novel.
A 100-foot long Liopluerodon appears in the novel Meg: Hell's Aquarium and is despicted as having evolved gills and being bigger than Megalodon.
A male Liopluerodon is featured in Sea Rex where he loses an eye and chases a plesiosaur before being dealt a fatal blow from the tail of a Leedsicthys.
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