Metriorhynchus
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 Metriorhynchus superciliosus
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Extinct (fossil)
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Metriorhynchus was a marine crocodyliform that lived in the oceans during the Middle to Late Jurassic Period. Metriorhynchus was a carnivore that spent much, if not all, its life out at sea. No Metriorhynchus eggs or nest have been discovered, so little is known of the reptile's lifecycle, unlike other large marine reptiles of the Mesozoic, such as plesiosaurs or ichthyosaurs which are known to give birth to live young out at sea. Where Metriorhynchus mated, whether on land or at sea, is currently unknown.
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[edit] Anatomy and morphology
Averaging around three metres in length, Metriorhynchus is compared to living crocodilians medium-sized, though size estimates for Metriorhynchus suggest it could grow to at least the size of modern saltwater crocodiles. Its body was streamlined for greater hydrodynamic swimming, which along with its finned tail made it a more efficient swimmer than modern crocodilian species.
[edit] Ecology and life history
Metriorhynchus was a versatile and opportunistic predator, predated upon both the armoured belemnites, fast moving fish and the giant filter feeding fish Leedsichthys. Occasionally it was also capable of capturing flying animals such as the pterosaurs and scavenging on plesiosaur carcassess on the sea-floor.
[edit] Predators
Even though Metriorhynchus was an effective predator, it was vulnerable to predation from super predators such as Liopleurodon which could grow in excess of 10 metres in length. Since Metriorhynchus had lost its osteoderms, "armour scutes", to become more efficient swimmers it would have had little defence against larger marine predators.
[edit] Taxonomic history
[edit] Species
Species in this genus are traditionally classed into two skull groups: longirostrine (long, narrow jaws) and brevirostrine (short, broad jaws).
Longirostrine
- M. superciliosus: Western Europe of the Middle-Late Jurassic (Callovian and Oxfordian stage)
- M. leedsi: Western Europe of the Middle Jurassic (Callovian)
- M. palpebrosus: Western Europe of the Late Jurassic (Kimmeridgian)
- M. hastifer: Western Europe of the Late Jurassic (Kimmeridgian)
- M. acutus: Western Europe of the Late Jurassic (Kimmidgian)
- M. geoffroyii: type species Western Europe of the Late Jurassic (Kimmeridgian)
Brevirostrine
- M. brachyrhynchus: Western Europe of the Middle-Late Jurassic (Callovian and Oxfordian)
- M. durobrivensis: Western Europe of the Middle Jurassic (Callovian). Was originally the type species of the genus Suchodus, but it was regarded as a junior synonym of Metriorhynchus by Andrews, 1913.
- M. casamiquelai: Middle Jurassic of Chile (Callovian)
- M. potens: End Jurassic of Argentina (Tithonian). Was originally the type species of the genus Purranisaurus, but it was regarded as a junior synonym of Metriorhynchus by Gasparini, 1975.
Fragmentary remains of Metriorhynchus are known from the Middle Jurassic ages of the Bajocian and Bathonian.
[edit] Closely related species
Metriorhynchus is the type genus for the Metriorhynchidae. Other genera included in this family are: Teleidosaurus, Geosaurus, Dakosaurus and Enaliosuchus. The genera within Metiorhynchidae considered to be nomina dubia are Aggiosaurus and Neustosaurus.
[edit] In Popular Culture
Metriorhynchus has featured in the Jurassic episode of the BBC television series Sea Monsters, and in the movie Ice Age 2: Meltdown.
[edit] References
- Adams-Tresman, S.M. (1987). The Callovian (Middle Jurassic) marine crocodile Metriorhynchus from Central England. Palaeontology 30 (1): 179-194
- Buffetaut, E. (1982). Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes. Mémoires Societé Geologique de France 142: 1–88
- Forrest, R. (2003). Evidence for scavenging by the marine crocodile Metriorhynchus on the carcass of a plesiosaur. Proceedings of the Geologists’ Association 114: 363-366
