''Geosaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of marine

crocodyliform Crocodyliformes is a clade of 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 only pseu ...

within the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Metriorhynchidae Metriorhynchidae is an extinct family (biology), 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 ...

, that lived during the

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

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 145& ...

. ''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 whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...

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 ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

, such as

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appea ...

s or

ichthyosaurs Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, alth ...

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: Greece 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 ...

'' 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 'gi ...

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

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

naturalist

Georges Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in na ...

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 thoug ...

, the line leading to modern

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

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

thalattosuchia Thalattosuchia is a clade of 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 members of Cro ...

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 ...

'' 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 Afri ...

, 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 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...

) 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 (biology), family Metriorhynchidae. The genus was established by Johann Andreas Wagner in 1858 for three skulls from the Tithonian (Late Ju ...

''.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 (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

analyses begun in 2005 did not support the

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

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'' 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 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 species that contains the biological type specim ...

''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 of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by ...

). 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 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...

). It was named in honour of

palaeontologist Albert-Félix de Lapparent, 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 is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...

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

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 In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

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 ''Rhacheosaurus'' is an extinct genus of marine crocodyliform belonging to the family Metriorhynchidae. The genus was established by Christian Erich Hermann von Meyer in 1831 for skeletal remains from the Tithonian (Late Jurassic) of Germany.Mey ...

'', 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 ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...

, UK. It was assigned to its own genus, ''

Torvoneustes ''Torvoneustes'' is an extinct genus of metriorhynchid thalattosuchian. It is known from skull and postcranial remains found in the Kimmeridge Clay Formation of Dorset and Wiltshire, England, and also from Oaxaca, Mexico . The holotype skull of ...

'' by Andrade ''et al.'', 2010. An unnamed specimen classified as ''Geosaurus'' was found in the Oxfordian Jagua Formation 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 ro ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...

.''Geosaurus''
at

Fossilworks Fossilworks is 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 crea ...

.org

Palaeobiology

Niche partitioning

Several species of metriorhynchids are known from the Mörnsheim Formation ( Solnhofen limestone, early Tithonian) of

Bavaria Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total l ...

, Germany: ''Geosaurus giganteus'', ''

Dakosaurus maximus ''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 ...

'', ''

Cricosaurus suevicus ''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 ...

'' and ''

''. It has been hypothesised that

niche partitioning In ecology, niche differentiation (also known as niche segregation, niche separation and niche partitioning) refers to the process by which competing species use the environment differently in a way that helps them to coexist. The competitive exclu ...

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 el, στενός , 'narrow' and el, σαῦρος , '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 w ...

'' 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 Early Cretaceous crocodylomorphs of Europe Jurassic reptiles 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