''Geosaurus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of marine

crocodyliform Crocodyliformes is a clade of Crurotarsi, crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the ...

within the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Metriorhynchidae Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period ( Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhynchid ...

, that lived during the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

and the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

. ''Geosaurus'' was a

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

that spent much, if not all, its life out at sea. No ''Geosaurus'' eggs or nests have been discovered, so little is known of the reptile's lifecycle, unlike other large marine reptiles of the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

, such as

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

s or

ichthyosaurs Ichthyosauria is an taxonomy (biology), order of large extinction, extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of ...

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 "Mother of Giants lizard", and is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

'' Ge''- ("Earth", the mythical mother of the

Giants A giant is a being of human appearance, sometimes of prodigious size and strength, common in folklore. Giant(s) or The Giant(s) may also refer to: Mythology and religion *Giants (Greek mythology) * Jötunn, a Germanic term often translated as 'g ...

) and - ("lizard"). The name ''Geosaurus'' was established by the

French French may refer to: * Something of, from, or related to France ** French language, which originated in France ** French people, a nation and ethnic group ** French cuisine, cooking traditions and practices Arts and media * The French (band), ...

naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

in 1824.Cuvier G. 1824. Sur les ossements fossiles de crocodiles, 5. In: Dufour & D'Occagne, eds. ''Recherches sur les ossements fossiles, 2nd édition''. Paris: 143-160

Description

''Geosaurus'' was a large marine reptile of the group

Crurotarsi Crurotarsi is a clade of archosauriform reptiles that includes crocodilians and stem-crocodilians and possibly bird-line archosaurs too if the extinct, crocodile-like phytosaurs are more distantly related to crocodiles than traditionally though ...

, the line leading to modern

crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...

ns. It was about long. Specifically, it was a "marine crocodile", or

thalattosuchia Thalattosuchia is a clade of mostly marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not member ...

n. ''Geosaurus'' was similar in appearance to the related ''

Dakosaurus ''Dakosaurus'' is an extinct genus of crocodylomorph within the family Metriorhynchidae that lived during the Late Jurassic and Early Cretaceous. It was large, with teeth that were serrated and compressed lateromedially (flattened from side to s ...

'' with a relatively short skull and curved teeth designed for slashing, which it likely used to attack large prey. Geosaurus giganteus holotype

Many early depictions of ''Geosaurus'' were based on a nearly complete specimen described by

Eberhard Fraas Eberhard Fraas (26 June 1862 – 6 March 1915) was a German scientist, geologist and paleontologist. He worked as a curator at the Stuttgarter Naturaliensammlung and discovered the dinosaurs of the Tendaguru formation in then German East Africa (n ...

, which Fraas classified as a distinct species of ''Geosaurus'', ''G. suevicus''. This specimen was found in Germany and dated to the late Jurassic (Late

Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 154.8 ±0.8 Ma and 149.2 ±0.7 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...

) period.Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' 57: 409-418. ''G. suevicus'' had a distinctively long, narrow snout filled with small, pointed teeth very different from skulls belonging to the type species. Further study and a redescription of ''Geosaurus'' published in 2009 showed that these long-snouted forms actually represent individuals of ''

Cricosaurus ''Cricosaurus'' is an extinct genus of marine crocodyliforms of the Late Jurassic. belonging to the family Metriorhynchidae. The genus was established by Johann Andreas Wagner in 1858 for three skulls from the Tithonian (Late Jurassic) of Germany ...

''.Young, Mark T., and Marco Brandalise de Andrade, 2009. "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.

Classification and species

Genera considered junior synonyms of ''Geosaurus'' include ''Brachytaenius'' and ''Halilimnosaurus ''.Steel R. 1973. ''Crocodylia. Handbuch der Paläoherpetologie, Teil 16''. Stuttgart: Gustav Fischer Verlag, 116 pp. Numerous species had been assigned to this genus since the 19th Century. However,

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses begun in 2005 did not support the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of ''Geosaurus''.Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). ''Journal of Vertebrate Paleontology'' 27 (3): 170A.Mueller-Töwe IJ. 2005. Phylogenetic relationships of the Thalattosuchia. ''Zitteliana'' A45: 211–213. Although some traditional species, such as ''G. suevicus'' and ''G. araucanensis'' formed a natural group,Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. ''Science'' 311: 70-73. ''

Enaliosuchus ''Enaliosuchus'' is a dubious genus of extinct marine crocodyliform within the family Metriorhynchidae that lived during the Valanginian stage of the Early Cretaceous. It is known from fossil remains found in France and Germany and it was first ...

'' is also within that group.Wilkinson LE, Young MT, Benton MJ. 2008. A new metriorhynchid crocodilian (Mesoeucrocodylia: Thalattosuchia) from the Kimmeridgian (Upper Jurassic) of Wiltshire, UK. ''Palaeontology'' 51 (6): 1307-1333. This, as well as further study showing that traditional metriorhynchid genera were not grouped based on actual relationships, necessitated almost all traditional species being removed from ''Geosaurus'' and reclassified elsewhere, as well as several species previously placed in other genera to be reclassified as species of ''Geosaurus''. The species included below follow this revised classification, presented by Young and Andrade in 2009.

Valid species

* The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

''Geosaurus giganteus'', meaning "giant Earth lizard", is known from Western Europe (Germany) of the Late Jurassic (Early

Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...

). It was originally named ''Lacerta gigantea'' by von Sömmerring.Sömmerring ST von. 1816. Ueber die ''Lacerta gigantea'' der Vorwelt. ''Denkschriften der Königlichen Akademie der Wisseschaften zu Münch'' 6: 37-59. * ''Geosaurus grandis'', first described by Wagner in 1858, was formerly considered a species of ''

''. It is known from a complete skull. * ''Geosaurus lapparenti'' is known from south-east France and dates to the early Cretaceous period (

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...

). It was named in honour of

palaeontologist

Albert-Félix de Lapparent Albert-Félix de Lapparent (; 1905–1975) was a French people, French Palaeontology, palaeontologist. He was also a Society of Saint-Sulpice, Sulpician priest. He undertook a number of fossil-hunting explorations in the Sahara desert. He contribute ...

, and is based upon isolated skull and post-cranial bones (neck and tail vertebrae and a partial pelvic girdle) from the Early Cretaceous (Valanginian) of France.Debelmas J, Strannoloubsky A. 1957. Découverte d’un crocodilien dans le Néocomien de La Martre (Var) ''Dacosaurus lapparenti'' n. sp. ''Travaux Laboratoire de Géologie de l’université de Grenoble'' 33: 89-99. It was originally classified as a species of ''

''. A large species of ''Geosaurus'' is known only from a single tooth from the Nusplingen Plattenkalk of

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

Cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

after Cau & Fanti (2010).

Reclassified species

In 2009, Young and de Andrade published a re-description of ''Geosaurus'', examining its relationships and the validity of species lumped into the genus. After performing a phylogenetic analysis of metriorhynchids, they found that many species were grouped in a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

manner or with the wrong genera. Specifically, they found that several species formerly classified as ''Geosaurus'', including ''G. suevicus'', ''G. saltillense'',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'' 5 (6): 785-794. ''G. vignaudi'',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. and ''G. araucanensis''Gasparini ZB, Dellapé D. 1976. Un nuevo cocodrilo marino (Thalattosuchia, Metriorhynchidae) de la Formación Vaca Muerta (Jurasico, Tithoniano) de la Provincia de Neuquén (República Argentina). ''Congreso Geológico Chileno'' 1: c1-c21. were actually examples of the related ''

''. '' Rhacheosaurus gracilis'', another long-snouted species, was also at one time considered a species of ''Geosaurus'' (as ''G. gracilis'').Meyer H von 1831. Neue fossile Reptilien aus der Ordung der Saurier. ''Nova Acta Academiae Leopoldino-Carolinae Curios'' 15 (2): 173-184. ''Geosaurus carpenteri'', also formerly referred to ''Dakosaurus'', is known from a partial skull. Teeth identical to the known teeth of this species are also known from

Yorkshire Yorkshire ( ) is an area of Northern England which was History of Yorkshire, historically a county. Despite no longer being used for administration, Yorkshire retains a strong regional identity. The county was named after its county town, the ...

, UK. It was assigned to its own genus, '' Torvoneustes'' by Andrade ''et al.'', 2010. An unnamed specimen classified as ''Geosaurus'' was found in the Oxfordian

Jagua Formation The Jagua Formation is a Late Jurassic (middle to late Oxfordian (stage), Oxfordian) geologic Formation (geology), formation in the Sierra de los Órganos and Sierra del Rosario mountain ranges in Pinar del Río Province, western Cuba. Plesiosaur ...

of Cuba,Gasparini ZB, Iturralde-Vinet M. 2001. Metriorhynchid crocodiles (Crocodyliformes) from the Oxfordian of Western cuba. ''Neues Jahrbuch für Geologie und Paläontologie, Monatshefte'' 9: 534–542. though further study has shown this species to be more closely related to ''Cricosaurus'' as well. Additionally, ''Geosaurus'' fossils have been reported from the

Vaca Muerta The Vaca Muerta Formation, commonly known as Vaca Muerta ( Spanish for ''dead cow''), is a geologic formation of Late Jurassic to Early Cretaceous age, located in the Neuquén Basin in northern Patagonia, Argentina. It is well known as the host ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

.''Geosaurus''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org

Palaeobiology

Niche partitioning

Several species of metriorhynchids are known from the Mörnsheim Formation (

Solnhofen limestone The Solnhofen Limestone or Solnhofen Plattenkalk, formally known as the Altmühltal Formation, is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organi ...

, early Tithonian) of

Bavaria Bavaria, officially the Free State of Bavaria, is a States of Germany, state in the southeast of Germany. With an area of , it is the list of German states by area, largest German state by land area, comprising approximately 1/5 of the total l ...

, Germany: ''Geosaurus giganteus'', '' Dakosaurus maximus'', '' Cricosaurus suevicus'' and '' Rhacheosaurus gracilis''. It has been hypothesised that

niche partitioning In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...

enabled several species of crocodyliforms to co-exist. The top predators of this Formation appear to be ''G. giganteus'' and ''D. maximus'', which were large, short-snouted species with serrated teeth. The long-snouted ''C. suevicus'' and ''R. gracilis'' would have fed mostly on fish, although the more lightly built ''Rhacheosaurus'' may have specialised towards feeding on small prey. In addition to these four species of metriorhynchids, a moderate-sized species of ''

Steneosaurus ''Steneosaurus'' (from , 'narrow' and , 'lizard') is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic (Callovian or early Oxfordian) of France. The genus has been used as a wastebasket taxon for thalattosuchian ...

'' was also contemporaneous.Andrade MB, Young MT. 2008
High diversity of thalattosuchian crocodylians and the niche partition in the Solnhofen Sea
. The 56th Symposium of Vertebrate Palaeontology and Comparative Anatomy

References

{{Taxonbar, from=Q1901163 Prehistoric pseudosuchian genera Prehistoric marine crocodylomorphs Late Jurassic crocodylomorphs of Europe Early Cretaceous crocodylomorphs of Europe Jurassic France Fossils of France Jurassic Germany Fossils of Germany Solnhofen fauna Jurassic United Kingdom Fossils of England Mesozoic reptiles of North America Jurassic Cuba Fossils of Cuba Mesozoic reptiles of South America Jurassic Argentina Cretaceous Argentina Fossils of Argentina Fossil taxa described in 1824 Taxa named by Georges Cuvier