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{{Short description|Extinct genus of reptiles}}
{{Italic title}}
{{Automatic taxobox
{{automatic Taxobox
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| fossil_range = [[Late Jurassic]] to [[Early Cretaceous]] ([[Tithonian]] to [[Valanginian]]), {{Fossil range|150|136}}
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|name = ''Geosaurus''
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| image = Geosaurus giganteus skull.jpg
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|fossil_range = [[Late Jurassic]]-[[Early Cretaceous]], {{Fossil range|150|136}}
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| image_caption = Skull of ''G. giganteus''
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| image = Geosaurus fossil.JPG
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| taxon = Geosaurus
| image_width = 250px
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| image_caption = Fossil specimen
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| type_species = {{extinct}}''Lacerta gigantea''
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| type_species_authority = [[Samuel Thomas von Sömmerring|Sömmerring]], 1816
| authority = [[Georges Cuvier|Cuvier]], 1824
| authority = [[Georges Cuvier|Cuvier]], 1824
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| type_species = {{extinct}}''Geosaurus giganteus''
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| type_species_authority = [[Samuel Thomas von Sömmerring|Sömmerring]], 1816
| subdivision_ranks = [[Species]]
| subdivision_ranks = [[Species]]
| subdivision = * {{extinct}}'''''G. giganteus''''' <small>(Sömmerring, 1816)</small>
| subdivision =
* {{extinct}}''G. giganteus'' <br><small>(Sömmerring, 1816)</small>
* {{extinct}}'''''G. grandis''''' <small>(Wagner, 1858)</small>
* {{extinct}}''G. grandis'' <br><small>(Wagner, 1858)</small>
* {{extinct}}'''''G. lapparenti''''' <small>(Debelmas & Strannoloubsky, 1957)</small>
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| synonyms = * ''Halilimnosaurus'' <small> Ritgen, 1826 <ref name="Ritgen, 1826">Ritgen CH. 1826. Becken der krokodilartigen Salzumpf-eideche. ''Nova Acta Academiae Leopoldino-Carolinae Curios'' '''13''' (1): 331-358.</ref></small>
* {{extinct}}''G. lapparenti'' <br><small>Debelmas & Strannoloubsky, 1957</small>
|synonyms =
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* ''Halilimnosaurus'' <small> Ritgen, 1826 <ref name="Ritgen, 1826">Ritgen CH. 1826. Becken der krokodilartigen Salzumpf-eideche. ''Nova Acta Academiae Leopoldino-Carolinae Curios'' '''13''' (1): 331-358.</ref></small>
* ''Brachytaenius'' <small> von Meyer, 1842 <ref name="von Meyer, 1842">Meyer H von 1842. ''Brachytaenius perennis'' aus dem dichten gelben Jurakalk von Aalen in Würtembertg. In: Meyer H von, Althaus GB, Münster G, eds. ''Beiträge zur Petrefacten-kunde''. Bayreuth: 22-23, & plate 7.</ref></small>
* ''Brachytaenius'' <small> von Meyer, 1842 <ref name="von Meyer, 1842">Meyer H von 1842. ''Brachytaenius perennis'' aus dem dichten gelben Jurakalk von Aalen in Würtembertg. In: Meyer H von, Althaus GB, Münster G, eds. ''Beiträge zur Petrefacten-kunde''. Bayreuth: 22-23, & plate 7.</ref></small>
}}
}}


'''''Geosaurus''''' is an extinct [[genus]] of marine [[crocodyliform]] within the [[family (biology)|family]] [[Metriorhynchidae]] that lived during the [[Late Jurassic]] to the [[Early Cretaceous]]. ''Geosaurus'' was a [[carnivore]] 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]], such as [[plesiosaur]]s 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 "Mother of Giants lizard", and is derived from the [[Ancient Greek|Greek]] ''[[Gaia (mythology)|Ge]]''- ("Earth", the mythical mother of the [[Giants (Greek mythology)|Giants]]) and {{lang|grc|[[wikt:σαῦρος|σαῦρος]]}} -''sauros'' ("lizard"). The name ''Geosaurus'' was established by the [[France|French]] [[Natural History|naturalist]] [[Georges Cuvier]] in 1824.<ref name="Cuvier, 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</ref>
'''''Geosaurus''''' is an extinct [[genus]] of marine [[crocodyliform]] within the [[family (biology)|family]] [[Metriorhynchidae]], that lived during the [[Late Jurassic]] and the [[Early Cretaceous]]. ''Geosaurus'' was a [[carnivore]] 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]], such as [[plesiosaur]]s 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 "Mother of Giants lizard", and is derived from the [[Ancient Greek|Greek]] ''[[Gaia (mythology)|Ge]]''- ("Earth", the mythical mother of the [[Giants (Greek mythology)|Giants]]) and {{lang|grc|[[wikt:σαῦρος|σαῦρος]]}} -{{lang|grc-Latn|sauros}} ("lizard"). The name ''Geosaurus'' was established by the [[France|French]] [[Natural History|naturalist]] [[Georges Cuvier]] in 1824.<ref name="Cuvier, 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</ref>

The modern Chinese term for ''Geosaurus'' is [[Dilong]] [[地]]龍 "earth dragon" ([[地]]龙 in simplified Chinese).<ref name="Carr, 1990">Carr M. 1990. [http://sealang.net/sala/archives/pdf4/carr1990chinese.pdf "Chinese Dragon Names"]. ''Linguistics of the Tibeto-Burman Area 13.2'':87-189.</ref> This contrasts to the [[dinosaur]] genus ''[[Dilong (dinosaur)|Dilong]]'' which was named from Chinese ''dilong'' 帝龍 "emperor dragon".


== Description ==
== Description ==
[[File:Geosaurus giganteus.png|thumb|left|Size of ''G. giganteus'']]
[[File:Geosaurus giganteus.png|thumb|left|Size of ''G. giganteus'']]
''Geosaurus'' was a large, marine reptile of the group [[Crurotarsi]], the line leading to modern [[crocodilia]]ns. Specifically, it was a "marine crocodile", or [[thalattosuchia]]n. ''Geosaurus'' was similar in appearance to the related ''[[Dakosaurus]]'' with a relatively short skull and curved teeth designed for slashing, which it likely used to attack large prey.
''Geosaurus'' was a large marine reptile of the group [[Crurotarsi]], the line leading to modern [[crocodilia]]ns. It was about {{cvt|2.5|-|3|m|ft}} long.<ref>{{cite journal|year=2011|last1=Young|first1=M.T.|last2=Bell|first2=M.A.|last3=de Andrade|first3=M.B.|last4=Brusatte|first4=S.L.|title=Body size estimation and evolution in metriorhynchid crocodylomorphs: implications for species diversification and niche partitioning|journal=Zoological Journal of the Linnean Society|volume=163|issue=4|pages=1199–1216|doi=10.1111/j.1096-3642.2011.00734.x|doi-access=free}}</ref> Specifically, it was a "marine crocodile", or [[thalattosuchia]]n. ''Geosaurus'' was similar in appearance to the related ''[[Dakosaurus]]'' with a relatively short skull and curved teeth designed for slashing, which it likely used to attack large prey.
[[File:Geosaurus giganteus holotype.jpg|thumb|left|[[Holotype]] skull of ''G. giganteus''.]]

Many early depictions of ''Geosaurus'' were based on a nearly complete specimen described by [[Eberhard Fraas]], 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]]) period.<ref name="Fraas, 1901">Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' '''57''': 409-418.</ref> ''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 re-description of ''Geosaurus'' published in 2009 showed that these long-snouted form actually represent individuals of ''[[Cricosaurus]]''.<ref name="Young&Andrade2009">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.</ref>
Many early depictions of ''Geosaurus'' were based on a nearly complete specimen described by [[Eberhard Fraas]], 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]]) period.<ref name="Fraas, 1901">Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' '''57''': 409-418.</ref> ''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]]''.<ref name="Young&Andrade2009">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.</ref>


== Classification and species ==
== Classification and species ==
Genera considered junior synonyms of ''Geosaurus'' include ''[[Brachytaenius]]'' and ''Halilimnosaurus ''.<ref name="Steel, 1973">Steel R. 1973. ''Crocodylia. Handbuch der Paläoherpetologie, Teil 16''. Stuttgart: Gustav Fischer Verlag, 116 pp.</ref> Numerous species had been assigned to this genus since the 19th Century. However, [[phylogenetic]] analyses begun in 2005 did not support the [[monophyly]] of ''Geosaurus''.<ref name="Young, 2007">Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). ''Journal of Vertebrate Paleontology'' '''27''' (3): 170A.</ref><ref name="Mueller-Töwe, 2005">Mueller-Töwe IJ. 2005. Phylogenetic relationships of the Thalattosuchia. ''Zitteliana'' '''A45''': 211–213.</ref> Although some traditional species, such as ''G. suevicus'' and ''G. araucanensis'' formed a [[monophyly|natural group]],<ref name="Gasparini''et al.'', 2006">Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. ''Science'' '''311''': 70-73.</ref> ''[[Enaliosuchus]]'' is also within that group.<ref name="Young, 2007"/><ref name="Wilkinson et al., 2008">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.</ref> 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''.<ref name="Young&Andrade2009"/>
Genera considered junior synonyms of ''Geosaurus'' include ''Brachytaenius'' and ''Halilimnosaurus ''.<ref name="Steel, 1973">Steel R. 1973. ''Crocodylia. Handbuch der Paläoherpetologie, Teil 16''. Stuttgart: Gustav Fischer Verlag, 116 pp.</ref> Numerous species had been assigned to this genus since the 19th Century. However, [[phylogenetic]] analyses begun in 2005 did not support the [[monophyly]] of ''Geosaurus''.<ref name="Young, 2007">Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). ''Journal of Vertebrate Paleontology'' '''27''' (3): 170A.</ref><ref name="Mueller-Töwe, 2005">Mueller-Töwe IJ. 2005. Phylogenetic relationships of the Thalattosuchia. ''Zitteliana'' '''A45''': 211–213.</ref> Although some traditional species, such as ''G. suevicus'' and ''G. araucanensis'' formed a [[monophyly|natural group]],<ref name="Gasparini''et al.'', 2006">Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. ''Science'' '''311''': 70-73.</ref> ''[[Enaliosuchus]]'' is also within that group.<ref name="Young, 2007"/><ref name="Wilkinson et al., 2008">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.</ref> 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''.<ref name="Young&Andrade2009"/>


The species included below follow this revised classification, presented by Young and Andrade in 2009.<ref name="Young&Andrade2009"/>
The species included below follow this revised classification, presented by Young and Andrade in 2009.<ref name="Young&Andrade2009"/>


===Valid species===
=== Valid species ===
* The [[type species]] ''Geosaurus giganteus'', meaning "giant Earth lizard", is known from Western Europe (Germany) of the Late Jurassic (Early [[Tithonian]]). It was originally named ''Lacerta gigantea'' by [[Samuel Thomas von Sömmerring|von Sömmerring]].<ref name="Soemmerring, 1816">Sömmerring ST von. 1816. Ueber die ''Lacerta gigantea'' der Vorwelt. ''Denkschriften der Königlichen Akademie der Wisseschaften zu Münch'' '''6''': 37-59.</ref>
* The [[type species]] ''Geosaurus giganteus'', meaning "giant Earth lizard", is known from Western Europe (Germany) of the Late Jurassic (Early [[Tithonian]]). It was originally named ''Lacerta gigantea'' by [[Samuel Thomas von Sömmerring|von Sömmerring]].<ref name="Soemmerring, 1816">Sömmerring ST von. 1816. Ueber die ''Lacerta gigantea'' der Vorwelt. ''Denkschriften der Königlichen Akademie der Wisseschaften zu Münch'' '''6''': 37-59.</ref>
* ''Geosaurus grandis'', first described by Wagner in 1858, was formerly considered a species of ''[[Cricosaurus]]''. It is known from a complete skull.
* ''Geosaurus grandis'', first described by Wagner in 1858, was formerly considered a species of ''[[Cricosaurus]]''. It is known from a complete skull.
* ''Geosaurus lapparenti'' is known from south-east France and dates to the early Cretaceous period ([[Valanginian]]). It was named in honour of [[France|French]] palaeontologist [[Albert-Félix de Lapparent]], and is based upon isolated skull and post-cranial bones (eck and tail vertebrae and a partial pelvic girdle) from the Early Cretaceous (Valanginian) of France.<ref name="Deblemas & Strannoloubsky, 1957">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.</ref> It was originally classified as a species of ''[[Dakosaurus]]''.
* ''Geosaurus lapparenti'' is known from south-east France and dates to the early Cretaceous period ([[Valanginian]]). It was named in honour of [[France|French]] 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.<ref name="Deblemas & Strannoloubsky, 1957">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.</ref> It was originally classified as a species of ''[[Dakosaurus]]''.


A new, previously unknown large species of ''Geosaurus'' known only from a single tooth from the Nusplingen Plattenkalk of [[Germany]].<ref name=Aetal10/>
A large species of ''Geosaurus'' is known only from a single tooth from the [[Nusplingen Plattenkalk]] of [[Germany]].<ref name=Aetal10/>


[[Cladogram]] after Cau & Fanti (2010).<ref name="cau2010">{{cite journal|authors=Andrea Cau; Federico Fanti |year=2010 |title=The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy: ''Neptunidraco ammoniticus'' gen. et sp. nov. |journal=Gondwana Research |volume=19 |doi=10.1016/j.gr.2010.07.007}}</ref>
[[Cladogram]] after Cau & Fanti (2010).<ref name="cau2010">{{cite journal|author1=Andrea Cau |author2=Federico Fanti |year=2010 |title=The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy: ''Neptunidraco ammoniticus'' gen. et sp. nov. |journal=Gondwana Research |volume=19 |issue=2 |pages=550–565 |doi=10.1016/j.gr.2010.07.007}}</ref>


{{clade| style=font-size:90%;line-height:85%
{{clade| style=font-size:90%;line-height:85%
|label1='''Geosaurus'''&nbsp;
|label1='''''Geosaurus'''''&nbsp;
|1={{clade
|1={{clade
|1=''G. lapparenti''
|1=''G. lapparenti''
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}} }} }}
}} }} }}


===Reclassified species===
=== 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]] manner or with the wrong genera. Specifically, they found that several species formerly classified as ''Geosaurus'', including ''G. suevicus'', ''G. saltillense'',<ref name="Buchy ''et al.'', 2006">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.</ref> ''G. vignaudi'',<ref name="Frey ''et al.'', 2002">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.</ref> and ''G. araucanensis''<ref name="Gaparini & Dellapé, 1976">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.</ref> were actually examples of the related ''[[Cricosaurus]]''.<ref name="Young&Andrade2009"/> ''[[Rhacheosaurus|Rhacheosaurus gracilis]]'', another long-snouted species, was also at one time considered a species of ''Geosaurus'' (as ''G. gracilis'').<ref name="Young&Andrade2009"/><ref name="von Meyer, 1831">Meyer H von 1831. Neue fossile Reptilien aus der Ordung der Saurier. ''Nova Acta Academiae Leopoldino-Carolinae Curios'' '''15''' (2): 173-184.</ref>
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]] manner or with the wrong genera. Specifically, they found that several species formerly classified as ''Geosaurus'', including ''G. suevicus'', ''G. saltillense'',<ref name="Buchy ''et al.'', 2006">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.</ref> ''G. vignaudi'',<ref name="Frey ''et al.'', 2002">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.</ref> and ''G. araucanensis''<ref name="Gaparini & Dellapé, 1976">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.</ref> were actually examples of the related ''[[Cricosaurus]]''.<ref name="Young&Andrade2009"/> ''[[Rhacheosaurus|Rhacheosaurus gracilis]]'', another long-snouted species, was also at one time considered a species of ''Geosaurus'' (as ''G. gracilis'').<ref name="Young&Andrade2009"/><ref name="von Meyer, 1831">Meyer H von 1831. Neue fossile Reptilien aus der Ordung der Saurier. ''Nova Acta Academiae Leopoldino-Carolinae Curios'' '''15''' (2): 173-184.</ref>


''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]], UK. It was assigned to its own genus, ''[[Torvoneustes]]'' by Andrade ''et al.'', 2010.<ref name=Aetal10>{{cite journal |last=Andrade |first=M.B.D. |author2=Young, M.T. |author3=Desojo, J.B. |author4= Brusatte, S.L. |year=2010 |title=The evolution of extreme hypercarnivory in Metriorhynchidae (Mesoeucrocodylia: Thalattosuchia) based on evidence from microscopic denticle morphology |journal=Journal of Vertebrate Paleontology |volume=30 |issue=5 |pages=1451–1465 |doi=10.1080/02724634.2010.501442}}</ref>
''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]], UK. It was assigned to its own genus, ''[[Torvoneustes]]'' by Andrade ''et al.'', 2010.<ref name=Aetal10>{{cite journal |last=Andrade |first=M.B.D. |author2=Young, M.T. |author3=Desojo, J.B. |author4= Brusatte, S.L. |year=2010 |title=The evolution of extreme hypercarnivory in Metriorhynchidae (Mesoeucrocodylia: Thalattosuchia) based on evidence from microscopic denticle morphology |journal=Journal of Vertebrate Paleontology |volume=30 |issue=5 |pages=1451–1465 |doi=10.1080/02724634.2010.501442|bibcode=2010JVPal..30.1451D |s2cid=83985855 |hdl=11336/69039 |hdl-access=free }}</ref>


An unnamed specimen classified as ''Geosaurus'' was found in [[Oxfordian stage|Oxfordian]] age rocks of Cuba,<ref name="Gasparini & Iturralde-Vinet, 2001">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.</ref> though further study has shown this species to be more closely related to ''Cricosaurus'' as well.<ref name="Young&Andrade2009"/>
An unnamed specimen classified as ''Geosaurus'' was found in the [[Oxfordian stage|Oxfordian]] [[Jagua Formation]] of Cuba,<ref name="Gasparini & Iturralde-Vinet, 2001">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.</ref> though further study has shown this species to be more closely related to ''Cricosaurus'' as well.<ref name="Young&Andrade2009"/>


Additionally, ''Geosaurus'' fossils have been reported from the [[Vaca Muerta]] of [[Argentina]].<ref name=FWGeosaurus>[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36592 ''Geosaurus''] at [[Fossilworks]].org</ref>
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==Palaeobiology==
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=== Niche partitioning ===
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Several species of metriorhynchids are known from the Mörnsheim Formation ([[Solnhofen limestone]], early Tithonian) of [[Bavaria]], Germany. Alongside ''[[Dakosaurus|Dakosaurus maximus]]'', three species of ''Geosaurus'' are known, including ''G. giganteus'', ''G. suevicus'' and ''G. gracilis''. It has been hypothesised that [[niche differentiation|niche partitioning]] enabled several species of crocodyliforms to co-exist. The top predators of this Formation appear to be ''Dakosaurus'' and ''G. giganteus'', which were large, short-snouted species with serrated teeth. The long-snouted ''G. suevicus'' and ''G. gracilis'' would have feed mostly on fish, although the more lightly built ''G. gracilis'' may have specialised towards feeding on small prey. In addition to four species of metriorhynchids, a moderate-sized species of ''[[Steneosaurus]]'' was also contemporaneous.<ref name="Andrade & Young, 2008">Andrade MB, Young MT. 2008. [http://www.svpca.org/general/pages/abstractPage.php?i=1378&r=talksAndPosters.php&y=2008 High diversity of thalattosuchian crocodylians and the niche partition in the Solnhofen Sea]. The 56th Symposium of Vertebrate Palaeontology and Comparative Anatomy</ref>


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== Palaeobiology ==
From the slightly older [[Nusplingen]] Plattenkalk (late Kimmeridgian) of southern Germany, both ''G. suevicus'' and ''Dakosaurus maximus'' are contemporaneous. As with Solnhofen, ''G. suevicus'' feed upon fish, while ''Dakosaurus'' was the top predator.<ref name="Dietl et al., 2000">Dietl G, Dietl O, Schweigert G, Hugger R. 2000. ''Der Nusplinger Plattenkalk (Weißer Jura zeta)'' - Grabungskampagne 1999.</ref>
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=== Niche partitioning ===
[[File:Geosaurus grandis holotype.jpg|thumb|left|Holotype skull of ''G. grandis'' from the [[Daiting]] locality.]]
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Several species of metriorhynchids are known from the Mörnsheim Formation ([[Solnhofen limestone]], early Tithonian) of [[Bavaria]], Germany: ''Geosaurus giganteus'', ''[[Dakosaurus maximus]]'', ''[[Cricosaurus suevicus]]'' and ''[[Rhacheosaurus gracilis]]''. It has been hypothesised that [[niche differentiation|niche partitioning]] 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]]'' was also contemporaneous.<ref name="Andrade & Young, 2008">Andrade MB, Young MT. 2008. [http://www.svpca.org/general/pages/abstractPage.php?i=1378&r=talksAndPosters.php&y=2008 High diversity of thalattosuchian crocodylians and the niche partition in the Solnhofen Sea] {{webarchive|url=https://web.archive.org/web/20110603232400/http://www.svpca.org/general/pages/abstractPage.php?i=1378&r=talksAndPosters.php&y=2008 |date=2011-06-03 }}. The 56th Symposium of Vertebrate Palaeontology and Comparative Anatomy</ref>


==See also==
== See also ==
{{portal|Paleontology}}
{{Portal|Paleontology}}
*[[List of marine reptiles]]
* [[List of marine reptiles]]


==References==
== References ==
{{reflist|2}}
{{Reflist}}


{{Thalattosuchia}}
{{Thalattosuchia}}
{{Taxonbar|from=Q1901163}}


[[Category:Marine crocodylomorphs]]
[[Category:Prehistoric pseudosuchian genera]]
[[Category:Jurassic crocodylomorpha]]
[[Category:Prehistoric marine crocodylomorphs]]
[[Category:Cretaceous crocodylomorpha]]
[[Category:Late Jurassic crocodylomorphs of Europe]]
[[Category:Early Cretaceous crocodylomorphs of Europe]]
[[Category:Jurassic France]]
[[Category:Fossils of France]]
[[Category:Jurassic Germany]]
[[Category:Fossils of Germany]]
[[Category:Solnhofen fauna]]
[[Category:Solnhofen fauna]]
[[Category:Prehistoric reptiles of North America]]
[[Category:Jurassic United Kingdom]]
[[Category:Prehistoric reptiles of Europe]]
[[Category:Fossils of England]]
[[Category:Prehistoric reptiles of South America]]
[[Category:Mesozoic reptiles of North America]]
[[Category:Jurassic Cuba]]
[[Category:Fossils of Cuba]]
[[Category:Mesozoic reptiles of South America]]
[[Category:Jurassic Argentina]]
[[Category:Cretaceous Argentina]]
[[Category:Fossils of Argentina]]
[[Category:Fossil taxa described in 1824]]
[[Category:Taxa named by Georges Cuvier]]

Latest revision as of 07:18, 18 November 2024

Geosaurus
Temporal range: Late Jurassic to Early Cretaceous (Tithonian to Valanginian), 150–136 Ma
Skull of G. giganteus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Crocodyliformes
Suborder: †Thalattosuchia
Family: †Metriorhynchidae
Subtribe: †Geosaurina
Genus: †Geosaurus
Cuvier, 1824
Type species
†Geosaurus giganteus
Species
  • †G. giganteus (Sömmerring, 1816)
  • †G. grandis (Wagner, 1858)
  • †G. lapparenti (Debelmas & Strannoloubsky, 1957)
Synonyms
  • Halilimnosaurus Ritgen, 1826 [1]
  • Brachytaenius von Meyer, 1842 [2]

Geosaurus is an extinct genus of marine crocodyliform within the family Metriorhynchidae, that lived during the Late Jurassic and the Early Cretaceous. Geosaurus was a carnivore 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, 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 "Mother of Giants lizard", and is derived from the Greek Ge- ("Earth", the mythical mother of the Giants) and σαῦρος -sauros ("lizard"). The name Geosaurus was established by the French naturalist Georges Cuvier in 1824.[3]

Description

[edit]
Size of G. giganteus

Geosaurus was a large marine reptile of the group Crurotarsi, the line leading to modern crocodilians. It was about 2.5–3 m (8.2–9.8 ft) long.[4] Specifically, it was a "marine crocodile", or thalattosuchian. Geosaurus was similar in appearance to the related Dakosaurus with a relatively short skull and curved teeth designed for slashing, which it likely used to attack large prey.

Holotype skull of G. giganteus.

Many early depictions of Geosaurus were based on a nearly complete specimen described by Eberhard Fraas, 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) period.[5] 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.[6]

Classification and species

[edit]

Genera considered junior synonyms of Geosaurus include Brachytaenius and Halilimnosaurus .[7] Numerous species had been assigned to this genus since the 19th Century. However, phylogenetic analyses begun in 2005 did not support the monophyly of Geosaurus.[8][9] Although some traditional species, such as G. suevicus and G. araucanensis formed a natural group,[10] Enaliosuchus is also within that group.[8][11] 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.[6]

The species included below follow this revised classification, presented by Young and Andrade in 2009.[6]

Valid species

[edit]
  • The type species Geosaurus giganteus, meaning "giant Earth lizard", is known from Western Europe (Germany) of the Late Jurassic (Early Tithonian). It was originally named Lacerta gigantea by von Sömmerring.[12]
  • Geosaurus grandis, first described by Wagner in 1858, was formerly considered a species of Cricosaurus. It is known from a complete skull.
  • Geosaurus lapparenti is known from south-east France and dates to the early Cretaceous period (Valanginian). It was named in honour of French 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.[13] It was originally classified as a species of Dakosaurus.

A large species of Geosaurus is known only from a single tooth from the Nusplingen Plattenkalk of Germany.[14]

Cladogram after Cau & Fanti (2010).[15]

Geosaurus 

G. lapparenti

G. grandis

G. giganteus

Reclassified species

[edit]

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 manner or with the wrong genera. Specifically, they found that several species formerly classified as Geosaurus, including G. suevicus, G. saltillense,[16] G. vignaudi,[17] and G. araucanensis[18] were actually examples of the related Cricosaurus.[6] Rhacheosaurus gracilis, another long-snouted species, was also at one time considered a species of Geosaurus (as G. gracilis).[6][19]

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, UK. It was assigned to its own genus, Torvoneustes by Andrade et al., 2010.[14]

An unnamed specimen classified as Geosaurus was found in the Oxfordian Jagua Formation of Cuba,[20] though further study has shown this species to be more closely related to Cricosaurus as well.[6]

Additionally, Geosaurus fossils have been reported from the Vaca Muerta of Argentina.[21]

Palaeobiology

[edit]

Niche partitioning

[edit]
Holotype skull of G. grandis from the Daiting locality.

Several species of metriorhynchids are known from the Mörnsheim Formation (Solnhofen limestone, early Tithonian) of Bavaria, Germany: Geosaurus giganteus, Dakosaurus maximus, Cricosaurus suevicus and Rhacheosaurus gracilis. It has been hypothesised that niche partitioning 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 was also contemporaneous.[22]

See also

[edit]

References

[edit]
  1. ^ Ritgen CH. 1826. Becken der krokodilartigen Salzumpf-eideche. Nova Acta Academiae Leopoldino-Carolinae Curios 13 (1): 331-358.
  2. ^ Meyer H von 1842. Brachytaenius perennis aus dem dichten gelben Jurakalk von Aalen in Würtembertg. In: Meyer H von, Althaus GB, Münster G, eds. Beiträge zur Petrefacten-kunde. Bayreuth: 22-23, & plate 7.
  3. ^ 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
  4. ^ Young, M.T.; Bell, M.A.; de Andrade, M.B.; Brusatte, S.L. (2011). "Body size estimation and evolution in metriorhynchid crocodylomorphs: implications for species diversification and niche partitioning". Zoological Journal of the Linnean Society. 163 (4): 1199–1216. doi:10.1111/j.1096-3642.2011.00734.x.
  5. ^ Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg 57: 409-418.
  6. ^ a b c d e f 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.
  7. ^ Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag, 116 pp.
  8. ^ a b Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). Journal of Vertebrate Paleontology 27 (3): 170A.
  9. ^ Mueller-Töwe IJ. 2005. Phylogenetic relationships of the Thalattosuchia. Zitteliana A45: 211–213.
  10. ^ Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. Science 311: 70-73.
  11. ^ 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.
  12. ^ Sömmerring ST von. 1816. Ueber die Lacerta gigantea der Vorwelt. Denkschriften der Königlichen Akademie der Wisseschaften zu Münch 6: 37-59.
  13. ^ 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.
  14. ^ a b Andrade, M.B.D.; Young, M.T.; Desojo, J.B.; Brusatte, S.L. (2010). "The evolution of extreme hypercarnivory in Metriorhynchidae (Mesoeucrocodylia: Thalattosuchia) based on evidence from microscopic denticle morphology". Journal of Vertebrate Paleontology. 30 (5): 1451–1465. Bibcode:2010JVPal..30.1451D. doi:10.1080/02724634.2010.501442. hdl:11336/69039. S2CID 83985855.
  15. ^ Andrea Cau; Federico Fanti (2010). "The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy: Neptunidraco ammoniticus gen. et sp. nov". Gondwana Research. 19 (2): 550–565. doi:10.1016/j.gr.2010.07.007.
  16. ^ 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.
  17. ^ 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.
  18. ^ 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.
  19. ^ Meyer H von 1831. Neue fossile Reptilien aus der Ordung der Saurier. Nova Acta Academiae Leopoldino-Carolinae Curios 15 (2): 173-184.
  20. ^ 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.
  21. ^ Geosaurus at Fossilworks.org
  22. ^ Andrade MB, Young MT. 2008. High diversity of thalattosuchian crocodylians and the niche partition in the Solnhofen Sea Archived 2011-06-03 at the Wayback Machine. The 56th Symposium of Vertebrate Palaeontology and Comparative Anatomy
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