Liopleurodon
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| Liopleurodon ferox (right) harassing Leedsichthys problematicus | |
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| Genus: | Liopleurodon Sauvage, 1873
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L. ferox Sauvage, 1873 (type) | |
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Strongylokroptaphus Novozhilov, 1964 | |
Liopleurodon (Template:PronEng, 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.
Discovery and species
The genus name Liopleurodon was coined by H.E Sauvage in 1873[1] 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 younger species known from Russia. Fossil specimens that are contemporary (Callovian) with those from England and France referrable to Liopleurodon are known from Germany.[2]
Currently, there are three recognized species within Liopleurodon. From the Callovian of England and France L. ferox is well known; while also from the Callovian of England is the rarer L. pachydeirus, described by Seeley as a Pliosaurus (1869).[3] From the Volgian of Russia, L. rossicus is known. This species was initially described by Novozhilov (1948) as belonging to Pliosaurus,[4] and is the type species of the genus Strongylokroptaphus.[5] Only L. ferox is known from more or less complete skeletons.
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 character in an ambush predator.[6][7] Studies of the skull have shown that it could probably scan the water with its nostrils to ascertain the source of certain smells.[8]
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.[9]
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 ft) to 10 meters (33 ft) long.[9]
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.[9]
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.[9] 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).[10] The genus Stretosaurus later became a junior synonym of Liopleurodon.[11] However, it has been re-classified as Pliosaurus macromerus.[12]
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 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.[13]
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. Two adult Eustreptospondylus 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.[14]
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.[15]
References
- ^ Sauvage HE. 1873. Notes sur les Reptiles fossiles. Bulletin de la Société Géologiques de France, series 3 4: 365-380.
- ^ Sachs S. 1997. Mesozoische Reptilien aus Nordrhein-Westfalen. In S. Sachs, O. W. M. Rauhut, & A. Weigert (eds.), Terra Nostra. 1. Treffen der deutschsprachigen Paläoherpetologen Düsseldorf: 22-27.
- ^ Seeley HG. 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 NI. 1948. Two new pliosaurs from the Lower Volga Beds Provolzhe (Right bank of Volga). Doklandy Akadamie Nauk SSSR, Moscow 60: 115-118.
- ^ Novozhilov NI. 1964. Order Sauropterygia. Osnovy Paleontologii 12: 309-332.
- ^ 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 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.
- ^ Buchy M-C, Frey E, Stinnesbeck W, López-Oliva JG. 2003. First occurrence of a gigantic pliosaurid plesiosaur in the late Jurassic (Kimmeridgian) of Mexico. Bulletin de la Société Géologique de France 174 (3): 271-278.
- ^ Disc Two of Walking with Dinosaurs DVD
- ^ Charlie and the Liopleurodon