Geosaurus
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| Geosaurus Fossil range: Middle Jurassic to Early Cretaceous |
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 Restoration of Geosaurus suevicus
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Geosaurus was a small, gracile genus of marine crocodylian within the family Metriorhynchidae. Geosaurus was a carnivore that spent much, if not all, its life out at sea. No Geosaurus 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 Geosaurus mated, whether on land or at sea, is currently unknown. The name Geosaurus means "Earth lizard", and is derived from the Greek Ge- ("Earth") and σαῦρος -sauros ("lizard"). The name Geosaurus was established by the French naturalist Georges Cuvier in 1824.
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[edit] Species
The species within Geosaurus include :
- G. giganteus: type species from Western Europe (Germany) of the Late Jurassic (Early Tithonian). Originally named Lacerta gigantea by von Sömmerring.
- G. gracilis: Western Europe (Germany) of the Late Jurassic (Early Tithonian). Was originally the type species of the genus Rhacheosaurus.
- G. suevicus: Western Europe (Germany) of the Late Jurassic (Late Kimmeridgian)
- G. saltillense: Mexico of the Late Jurassic (Early Tithonian)
- G. vignaudi: Mexico of the Late Jurassic (Middle Tithonian)
- G. araucanensis: Argentina of the Late Jurassic (Early Tithonian)
Synonyms of this genus include: Brachytaenius, Rhacheosaurus and Halilimnosaurus .
[edit] Size and form
With all currently known species being three metres or less in length, Geosaurus is somewhat small when compared to living crocodilians. Its body was highly streamlined for greater hydrodynamic swimming, which along with finned tail made it a more efficient swimmer than modern crocodilian species.
[edit] Closely related species
Other genera included within the metriorhynchid family are: Teleidosaurus, Metriorhynchus, Dakosaurus and Enaliosuchus. The genera within Metiorhynchidae considered to be nomina dubia are Aggiosaurus and Neustosaurus.
[edit] References
- Buchy, M.-C., Vignaud, P., Frey, E., Stinnesbeck, W. & González, A.H.G. (2006). A new thalattosuchian crocodyliform from the Tithonian (Upper Jurassic) of northeastern Mexico. Comptes Rendus Palevol (in press)
- Frey, E., Buchy, M.-C., Stinnesbeck, W. & López-Oliva, J.G. (2002). Geosaurus vignaudi n. sp. (Crocodylia, Thalattosuchia), first evidence of metriorhynchid crocodilians in the Late Jurassic (Tithonian) of central-east Mexico (State of Puebla). Canadian Journal of Earth Sciences 39: 1467–1483
