Liopleurodon
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| Liopleurodon Fossil range: Middle - Late Jurassic |
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 Liopleurodon ferox (right) harassing Leedsichthys problematicus
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L. ferox (Sauvage, 1873 (type)) |
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 lived during the Callovian stage of the Middle Jurassic Period (c. 160 million to 155 million years ago mya), while the third, L. rossicus, lived during the Late Jurassic. It was the apex predator of the Middle to Late Jurassic seas that covered Europe.
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[edit] Anatomy, morphology and physiology
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 character in an ambush predator.[1][2] Studies of the skull have showed that it could probably scan the water with its nostrils to ascertain the source of certain smells.[3]
[edit] Size issue
Estimating the maximum size of Liopleurodon has become a controversial subject. The paleontologist L. B. Tarlo derived that the total body length of a pliosaur (including Liopleurodon) can be estimated from skull length, in which the skull is approximately one seventh of the entire body. The largest known skull belongs to L. ferox (1.5 meters in length), and according to Tarlo's estimation, this individual would be about 11 m (38 ft) long. However, as with its relative Kronosaurus, there is some uncertainty as to whether Tarlo's estimations are correct.[4]
Recent studies on pliosaurs have cast doubt on Tarlo's estimations, and indicate that pliosaur skulls were about one-fifth of the total body length. Hence, the average size of the L. ferox would have ranged from 7 meters (23 feet) to 10 meters (33 feet) long.[4]
The size estimate of Liopleurodon from the 1999 BBC series Walking with Dinosaurs, which depicts an enormous 25 meter-long Liopleurodon, is not considered to be accurate for any species of Liopleurodon.[4]
Pliosaur remains excavated from Kimmeridge Clay Formation of England indicate a much larger taxon, possibly up to 15 meters (49.2 feet long), existed, however they have not been identified as being to Liopleurodon.[4] A mandible on display in the Oxford University Museum of Natural History estimated over 3 meters (preserved 2.875m) was at one time classified as Liopleurodon macromerus. When the mandible was described, it was originally assigned to Stretosaurus (as Stretosaurus macromerus).[5] The genus Stretosaurus later became a junior synonym of Liopleurodon.[6] However, it has been re-classified as Pliosaurus macromerus.[7]
The discovery of an another very large pliosaur was announced in 2002, from Mexico. This pliosaur came to be known as the 'Monster of Aramberri'. The size of this specimen has been estimated to be about 15 meters (49.2 feet) long and it had a 10 foot long skull. Consequently, although widely reported as such, it does not belong to the genus Liopleurodon.[4] The remains of this animal consisting of a partial vertebral column, were dated to the Kimmeridgian of the La Caja Formation.[8] The fossils were actually found much earlier in 1985 by a geology student and were at first erroneously attributed to a theropod dinosaur by Hahnel.[9] The remains also originally contained part of a rostrum with teeth (now lost).
[edit] Range and distribution
Liopleurodon fossils have been found mainly in Germany, France, Russia and the United Kingdom, from the Middle to Late Jurassic. During this time Europe was covered by a shallow, epicontinental sea.
[edit] Evolutionary history
[edit] Discovery
The genus name Liopleurodon was coined by H.E Sauvage in 1873 [10] 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.
Currently, their are three recognized species within the genus Liopleurodon: L. ferox from the Callovian of England and France, L. pachydeirus from the Callovian of England, described by Seeley as a Pliosaurus (1869), [11], L. rossicus from the Volgian of Russia described by Novozhilov (1948) also as a Pliosaurus.[12] Only L. ferox is known from more or less complete skeletons.
[edit] In popular culture
In 1999, Liopleurodon was featured in an episode the BBC television series Walking with Dinosaurs. In the program, Liopleurodon was depicted attacking and devouring the theropod dinosaur Eustreptospondylus, before becoming beached during a typhoon and suffocating under its own weight. 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.[13]
[edit] References
- ^ Long Jr, J. H., Schumacher, J., Livingston, N. and Kemp, M., (2006) "Four flippers or two? Tetrapodal swimming with an aquatic robot" Bioinspir. & Biomim. 1(March 2006) pp. 20-29
- ^ "Swimming Robot Tests Theories About Locomotion In Existing And Extinct Animals".
- ^ Carpenter, K (1997), "Comparative cranial anatomy of two North American Cretaceous plesiosaurs", in JM Callaway & EL Nicholls (eds.), Ancient Marine Reptiles Academic Press, pp. 191-216.
- ^ a b c d e Forrest, Richard. Liopleurodon.
- ^ Tarlo, L. B. (1959) "Stretosaurus gen. nov., a giant pliosaur from the Kimeridge Clay"
- ^ Halstead, L. B. (1989). Plesiosaur locomotion. Journal of the Geological Society, London 146, 37-40.
- ^ Noè, L. F., Smith, D. T. J. & Walton, D. I. (2004). "A new species of Kimmeridgian pliosaur (Reptilia; Sauropterygia) and its bearing on the nomenclature of Liopleurodon macromerus". Proceedings of the Geologists' Association 115, 13-24.
- ^ M.-C. Buchy, E. Frey, W. Stinnesbeck, J.-G. Lopez-Oliva (2003) "First occurrence of a gigantic pliosaurid plesiosaur in the late Jurassic (Kimmeridgian) of Mexico", Bull. Soc. geol. Fr., 174(3), pp. 271-278
- ^ Hahnel W. (1988) "Hallazgo de restos de dinosaurio en Aramberri, N.L., Mexico",Actas Fac. Cienc. Tierra UANL Linares, 3, 245-250.
- ^ Sauvage, H. E. (1873). Notes sur les Reptiles fossiles. Bulletin de la Société Géologiques de France, series 3, n. 4 , p. 365-380
- ^ Seeley, H. G. (1869) "Index to the Fossil remains of Aves, Ornithosauria, and Reptilia, from the Secondary System of Strata arranged in the Woodwardian Museum of the University of Cambridge"
- ^ Novozhilov, N. I. (1948) "Two new pliosaurs from the Lower Volga Beds Provolzhe (Right bank of Volga)", Doklandy Akadamie Nauk SSSR, Moscow, v. 60, p. 115-118.
- ^ Disc Two of Walking with Dinosaurs DVD
