Geosaurus
Name: Geosaurus
(Earth lizard).
Phonetic: Jee-oh-sore-us.
Named By: Georges Cuvier - 1824.
Synonyms: Brachytaenius, Halilimnosaurus.
Classification: Chordata, Reptilia,
Archosauromorpha, Crurotarsi, Crocodylomorpha,
Mesoeucrocodylia, Thalattosuchia, Metriorhynchidae.
Species: G. giganteus (type),
G.
grandis, G. lapparenti.
Diet: Piscivore.
Size: Around 3 meters long.
Known locations: France and Germany.
Time period: Tithonian of the Jurassic through to
Valanginian of the Cretaceous.
Fossil representation: Multiple specimen
There
is some confusion regarding Geosaurus
reconstructions as there were
once both long and short snouted forms of the genus. One former
species of Geosaurus in particular known as G.
suevicus was an almost
complete specimen which was commonly used as a base for the majority of
early Geosaurus reconstructions. Later analysis
in 2009 by Mark
T. Young and Marco Brandalise de Andrade however found this fossil to
actually be a specimen of another marine crocodile
named Cricosaurus.
As such modern depictions of Geosaurus, find
that it is actually
more similar to Dakosaurus
in appearance.
As
with Dakosaurus, Geosaurus is
today thought to have been a short
snouted marine crocodile that had large serrated teeth. With this
kind of mouth and dentition, Geosaurus would have
been a more
effective predator of larger fish and potentially even other marine
reptiles. Former species of Geosaurus which are
now assigned to
Cricosaurus indicate that this would have been a
form of niche
partitioning which allowed several species of marine crocodile to
co-exist in the same ecosystem. This would see marine crocodiles like
Geosaurus and Dakosaurus taking
large prey, while Cricosaurus fed on
prey like small fish which it could more easily catch with its longer
jaws that had smaller but more numerous teeth.
Further reading
- Brachytaenius perennis aus dem dichten gelben
Jurakalk von Aalen in
W�rtembertg. In: Meyer H von, Althaus GB, M�nster G, eds. - Beitr�ge
zur Petrefacten-kunde. Bayreuth: 22-23, & plate 7 - H. von
Meyer - 1842.
- D�couverte d’un crocodilien dans le N�ocomien de La Martre (Var)
Dacosaurus lapparenti n. sp. - Travaux du Laboratoire de la Facult� des
Sciences de l'Universit� de Grenoble 33:89-99 - J. Debelmas &
A. Strannoloubsky - 1957.
- Geosaurus vignaudi n. sp. (Crocodylia,
Thalattosuchia), first
evidence of metriorhynchid crocodilians in the Late Jurassic
(Tithonian) of central-east Mexico (State of Puebla) - E. Frey, M. -C.
Buchy, W. Stinnesbeck & J. G. L�pez-Oliva - 2002.
- A new thalattosuchian crocodyliform from the Tithonian (Upper
Jurassic) of northeastern Mexico - Comptes Rendus Palevol 5 (6):
785-794 - M. -C. Buchy, P. Vignaud, E. Frey, W. Stinnesbeck &
A. H. G. Gonz�lez - 2006.
- The evolution and interrelationships of Metriorhynchidae
(Crocodyliformes, Thalattosuchia). - Journal of Vertebrate Paleontology
27 (3): 170A - M. T. young - 2007.
- What is Geosaurus? Redescription of Geosaurus giganteus
(Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern,
Germany. - Zoological Journal of the Linnean Society, 157: 551-585. -
Mark T. Young & Marco Brandalise de Andrade - 2009.
- The oldest known metriorhynchid crocodylian from the Middle Jurassic
of North-eastern Italy - Neptunidraco ammoniticus gen. et sp. nov.".
Gondwana Research 19 - Andrea Cau & Federico Fanti - 2010.
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