{{short description|Genus of extinct marine reptile, type genus of Ichthyosauria}} {{Use dmy dates|date=April 2022}} {{Automatic taxobox | fossil_range = Jurassic<br>{{fossil range|199.5|192.9}}<small>Possible Late Triassic (Rhaetian) record, but yet to be confirmed</small><ref name=Lomax2019>{{cite web|last1=Lomax|first1=D.R.|year=2019|title=A revision of Ichthyosaurus (Reptilia, Ichthyosauria)|publisher=Manchester eScholar|location=The University of Manchester|url=https://www.research.manchester.ac.uk/portal/files/127924285/FULL_TEXT.PDF|pages=1–414|s2cid=210305170}}</ref> | image = Ichthyosaurus BW.jpg | image_caption = Life reconstruction of ''Ichthyosaurus communis'' | image2 = Ichthyosaurus communis in London.jpg | image2_caption = Fossil specimen of ''Ichthyosaurus somersetensis'' at Natural History Museum, London (NHMUK PV OR 2013) | taxon = Ichthyosaurus | authority = Beche and Conybeare, 1821 | type_species = {{extinct}}''Ichthyosaurus communis'' | type_species_authority = Beche and Conybeare, 1822 | subdivision_ranks = Other species | subdivision = *{{extinct}}''Ichthyosaurus breviceps'' *{{extinct}}''Ichthyosaurus conybeari'' *{{extinct}}''Ichthyosaurus anningae'' *{{extinct}}''Ichthyosaurus larkini'' *{{extinct}}''Ichthyosaurus somersetensis'' }}
'''''Ichthyosaurus''''' (derived from Greek {{lang|grc|ἰχθύς}} ({{lang|grc-Latn|ichthys}}) meaning 'fish' and {{lang|grc|σαῦρος}} ({{lang|grc-Latn|sauros}}) meaning 'lizard') is an extinct genus of ichthyosaurs from the Early Jurassic (Hettangian - Pliensbachian)<ref>{{cite journal|author-link1=Dean Lomax |author1=Dean R. Lomax |year=2010 |title=An ''Ichthyosaurus'' (Reptilia, Ichthyosauria) with gastric contents from Charmouth, England: First report of the genus from the Pliensbachian |journal=Paludicola |volume=8 |issue=1 |pages=22–36 }}</ref> of Europe (Belgium, England, Germany and Portugal).<ref>{{Cite journal|last1=Sousa|first1=João|last2=Mateus|first2=Octávio|date=2021-09-09|title=The southernmost occurrence of Ichthyosaurus from the Sinemurian of Portugal|url=https://fr.copernicus.org/articles/24/287/2021/|journal=Fossil Record|language=English|volume=24|issue=2|pages=287–294|doi=10.5194/fr-24-287-2021|s2cid=239059696|issn=2193-0066|doi-access=free|bibcode=2021FossR..24..287S |hdl=10362/131844|hdl-access=free}}</ref> Some specimens of the ichthyosaurid ''Protoichthyosaurus'' from England and Switzerland have been erroneously referred to this genus in the past.<ref>{{cite journal|last1=Lomax|first1=D. R.|last2=Porro|first2=L. B.|last3=Larkin|first3=N. R.|year=2019|title=Descriptive anatomy of the largest known specimen of ''Protoichthyosaurus prostaxalis'' (Reptilia: Ichthyosauria) including computed tomography and digital reconstruction of a three-dimensional skull|journal=PeerJ|volume=7|article-number=e6112 |doi=10.7717/peerj.6112|pmid=30643690|pmc=6329338 |doi-access=free }}</ref><ref>{{cite journal|author1=Klug, C.|author2=Sivgin, T.|author3=Miedema, F.|author4=Scheffold, B.|author5=Reisdorf, A.G.|author6=Stössel, I.|author7=Maxwell, E.E.|author8=Scheyer, T.M.|year=2024|title=Swiss ichthyosaurs: a review|journal=Swiss Journal of Palaeontology|volume=143|at=31|doi=10.1186/s13358-024-00327-4|doi-access=free |pmc=11366730}}</ref> It is among the best known ichthyosaur genera, as it is the type genus of the order Ichthyosauria.<ref name="Maisch & Matzke, 2000">Maisch MW, Matzke AT. 2000. The Ichthyosauria. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' '''298''': 1-159</ref><ref name="McGowan & Motani, 2003">McGowan C, Motani R. 2003. Ichthyopterygia. – In: Sues, H.-D. (ed.): ''Handbook of Paleoherpetology, Part 8, Verlag Dr. Friedrich Pfeil'', 175 pp., 101 figs., 19 plts; München</ref>
==History of discovery== [[File:First complete ichthyosaur skeleton.jpg|thumb|left|Cast of the first known complete ''Ichthyosaurus'' specimen (originally referred to as ''Proteosaurus''), which was destroyed during World War 2]] ''Ichthyosaurus'' was the first complete fossil to be discovered in the early 19th century by Mary Anning in England;<ref>Essesials of Anthropology 6th addition</ref>{{incomplete citation|date=April 2026}} the holotype of ''I. communis'', no coll. number given,<ref name="ML18">{{cite journal |last1=Massare |first1=Judy A. |last2=Lomax |first2=Dean R. |title=A taxonomic reassessment of ''Ichthyosaurus communis'' and ''I. intermedius'' and a revised diagnosis for the genus |journal=Journal of Systematic Palaeontology |volume=16 |issue=3 |date=2018-02-19 |issn=1477-2019 |doi=10.1080/14772019.2017.1291116 |pages=263–277 |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2017.1291116 |access-date=2026-04-14}}</ref> was a fairly complete specimen discovered by Mary and Joseph Anning around 1814 in Lyme Regis<ref name="Home 1814">{{cite book |last=Home |first=Evard |author-link=Sir Everard Home|title=Some account of the fossil remains of an animal more nearly allied to fishes than any of the other classes of animals |year=1814 |via=Wellcome Collection |url=https://wellcomecollection.org/works/aahagru2 |oclc=969520454}}</ref> but was reported as lost by McGowan (1974) in his review of the latipinnate ichthyosaurs of England.<ref name="McGowan 1974">{{cite book |last=McGowan |first=Christopher |title=A revision of the Longipinnate Ichthyosaurs of the Lower Jurassic of England: with descriptions of two new species (Reptilia: Ichthyosauria) |publisher=Royal Ontario Museum |publication-place=Toronto |date=1974 |isbn=978-0-88854-151-2 |url=https://archive.org/details/revisionoflongip00mcgo/page/n1/mode/2up |via=Internet Archive |oclc=1126140010}}</ref> The name ''Ichthyosaurus'' was first used by Charles Konig in 1818, but it was not used in a formal scientific description, with the earliest described ichthyosaur being ''Proteosaurus'' by James Everard Home in 1819 for a skeleton which is now attributed to ''Temnodontosaurus platyodon.'' Henry Beche and William Conybeare in 1821 considered ''Ichthyosaurus'' to have taxonomic priority over ''Proteosaurus'' and named the species ''I. communis'' based on BMNH 2149 (now NHMUK PV R1158), a now partially lost specimen now assigned to ''Temnodontosaurus'' that was discovered and collected between 1811 and 1812.<ref name="De La Beche & Conybeare 1821">{{cite book |last1=De La Beche |first1=Henry T. |author1-link=Henry De la Beche |last2=Conybeare |first2=William Daniel |author2-link=William Conybeare (geologist) |title=Notice of a discovery of a new fossil animal, forming a link between the ''ichthyosaurus'' and crocodile |publisher=W. Phillips |publication-place=London |year=1821 |url=https://catalog.hathitrust.org/Record/012306790 |via=HathiTrust |oclc=882415891}}</ref><ref name=Conybeare1822>{{cite journal |last=Conybeare |first=William D. |author-link=William Conybeare (geologist) |title=IX.—Additional Notices on the Fossil Genera Ichthyosaurus and Plesiosaurus. |journal=Transactions of the Geological Society of London |volume=1 |issue=1 |date=1822 |issn=2042-5295 |doi=10.1144/transgslb.1.1.103 |pages=103–123 |url=https://www.lyellcollection.org/doi/10.1144/transgslb.1.1.103 |oclc=4648411970|url-access=subscription }}</ref> One specimen that Home had assigned to ''Proteosaurus'' was the first complete ichthyosaur skeleton known, but it was destroyed during World War 2. Two casts were rediscovered in 2022, showing that the specimen belonged to ''Ichthyosaurus'', but of uncertain species.<ref name="Proteosaurus">{{cite journal |last1=Lomax |first1=Dean R. |last2=Massare |first2=Judy A. |title=Rediscovery of two casts of the historically important ' Proteo-saurus ', the first complete ichthyosaur skeleton |journal=Royal Society Open Science |date=2022 |volume=9 |issue=11 |doi=10.1098/rsos.220966 |doi-access=free|pmid=36405641 |pmc=9626254 |bibcode=2022RSOS....920966L }}</ref> During the 19th century, almost all fossil ichthyosaurs were attributed to ''Ichthyosaurus'', resulting in the genus having over 50 species by 1900. These species were subsequently moved to separate genera or synonymised with other species.<ref name="Lomax2015" />
''I. anningae'', described in 2015 from a fossil found in the early 1980s in Dorset, England, was named after Anning.<ref name="Gill">{{cite web|url=https://www.bbc.co.uk/news/science-environment-31521719|title=BBC News - Forgotten fossil found to be new species of ichthyosaur|last=Gill|first=Victoria|date=19 February 2015|work=BBC Online|access-date=22 February 2015}}</ref><ref name="DonnyC">{{cite web|url=http://www.doncaster.gov.uk/db/enews/article.asp?Archive=&CatID=31&Art=6211|title=New species discovered in Doncaster|date=19 February 2015|access-date=22 February 2015|archive-url=https://web.archive.org/web/20150222185509/http://www.doncaster.gov.uk/db/enews/article.asp?Archive=&CatID=31&Art=6211|archive-date=22 February 2015}}</ref><ref name="Lomax2015">{{cite journal|last1=Lomax |first1=Dean R. |last2=Massare |first2=Judy A. |year=2015|title=A new species of Ichthyosaurusfrom the Lower Jurassic of West Dorset, England, U.K.|journal=Journal of Vertebrate Paleontology|volume=35 |issue=2 |article-number=e903260|issn=0272-4634|doi=10.1080/02724634.2014.903260|bibcode=2015JVPal..35E3260L |s2cid=85745787 |url=http://zoobank.org/urn:lsid:zoobank.org:pub:A5778FB5-A116-480A-93CA-AFC932ACAB55}}</ref> The fossil was acquired by Doncaster Museum and Art Gallery, where it was misidentified as a plaster cast. In 2008, Dean Lomax, from the University of Manchester, recognised it as genuine and worked with Judy Massare, of the State University of New York, to establish it as a new species.<ref name="Gill" />
==Description== thumb|right|Size comparison ''Ichthyosaurus'' was smaller than most of its relatives, with the largest specimen of ''I. somersetensis'' measuring up to {{cvt|3|-|3.3|m|ft}} in length.<ref name="bigsp">{{cite journal | last1 = Lomax | first1 = D.R. | last2 = Sachs | first2 = S. | title = On the largest ''Ichthyosaurus'': A new specimen of ''Ichthyosaurus somersetensis'' containing an embryo. | journal = Acta Palaeontologica Polonica | doi = 10.4202/app.00376.2017 | url = http://app.pan.pl/article/item/app003762017.html | date = 2017| volume = 62 | doi-access = free }}</ref> In comparison, other species were much smaller, with the ''I. communis'' reaching up to {{convert|2|m|ft}} in length, ''I. larkini'' probably up to {{convert|2.5|m|ft}}, ''I. anningae'' up to {{convert|1.8|m|ft}}, ''I. breviceps'' up to {{convert|1.9|m|ft}}, and ''I. conybeari'' up to {{convert|1.5|m|ft}}.<ref name=Lomax2019/><ref name=ML18/> Many ''Ichthyosaurus'' fossils are well-preserved and fully articulated. Some fossils still had baby specimens inside them, indicating that ''Ichthyosaurus'' was viviparous. Similar finds in the related ''Stenopterygius'' also show this.<ref name="Böttcher, 1990">Böttcher R. 1990. Neue Erkenntnisse über die Fortpflanzungsbiologie der Ichthyosaurier. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' '''164''': 1-51</ref><ref name="Martill, 1993">Martill D.M. 1993. Soupy Substrates: A Medium for the Exceptional Preservation of Ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany. ''Kaupia - Darmstädter Beiträge zur Naturgeschichte'' '''2''': 77-97</ref> Jurassic ichthyosaurs had a fleshy dorsal fin on their back as well as a large caudal fin. ''Icthyosaurus'' is distinguished from other ichthyosaurs by having a wide forefin with 5 or more digits with an anterior digital bifurcation, but the morphology of the humerus and coracoids are also distinct from that of other Lower Jurassic ichthyosaurs, as is the arrangement of the dermal bones, though the suture lines used to diagnose these are not always visible.<ref name="Lomax2015" />
== Classification == thumb|right|Skeleton of ''Ichthyosaurus breviceps'' *{{extinct}}''Ichthyosaurus communis'' (Beche and Conybeare, 1822) *{{extinct}}''Ichthyosaurus breviceps'' (Owen, 1881) *{{extinct}}''Ichthyosaurus conybeari'' (Lydekker, 1888) *{{extinct}}''Ichthyosaurus anningae'' (Lomax and Massare, 2015) *{{extinct}}''Ichthyosaurus larkini'' (Lomax and Massare, 2017)<ref name=PPIchthyosaurus>{{cite journal |author1=Dean R. Lomax |author2=Judy A. Massare |year=2017 |title=Two new species of ''Ichthyosaurus'' from the lowermost Jurassic (Hettangian) of Somerset, England |journal=Papers in Palaeontology |volume=3 |issue=1 |pages= 1–20|doi=10.1002/spp2.1065 |bibcode=2017PPal....3....1L |s2cid=89567182 }}</ref> *{{extinct}}''Ichthyosaurus somersetensis'' (Lomax and Massare, 2017)<ref name=PPIchthyosaurus />
===Cladogram=== This cladogram follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell.<ref name="DM10">{{cite journal|last1=Druckenmiller|first1=P. M.|last2=Maxwell|first2=E. E.|year=2010|title=A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada|journal=Canadian Journal of Earth Sciences|volume=47|issue=8|pages=1037–1053|doi=10.1139/E10-028|bibcode=2010CaJES..47.1037D}}</ref>
{{clade| style=font-size:85%;line-height:85% |label1=Thunnosauria |1={{clade |1='''''Ichthyosaurus'' ''' |2={{clade |1=''Stenopterygius'' |2={{clade |1=''Baptanodon'' |label2=Ophthalmosauridae |2={{clade |1={{clade |1=''Aegirosaurus'' |2=''Ophthalmosaurus'' <small>(type species)</small> }} |2={{clade |1=''Mollesaurus'' |2={{clade |1=''Athabascasaurus'' |2={{clade |1=''Brachypterygius'' |2={{clade |1=''Arthropterygius'' |2=''Caypullisaurus'' |3=''"Platypterygius" hercynicus'' |4=''"Platypterygius" australis'' (=''Longirostria'')<ref name=Platypterygius>Arkhangel'sky, M. S., 1998, On the Ichthyosaurian Genus Platypterygius: Palaeontological Journal, v. 32, n. 6, p. 611-615.</ref> |5=''Platypterygius'' <small>(type species)</small> |6={{clade |1=''Maiaspondylus'' |2=''"Platypterygius" americanus'' (=''Tenuirostria'')<ref name=Platypterygius/> }} }} }} }} }} }} }} }} }} }}
==Palaeobiology== thumb|Restoration of three ''Ichthyosaurus anningae'' ''Ichthyosaurus'' is suggested to have been a ram feeder, with the morphology of its hyobranchial apparatus suggesting that it was incapable of suction feeding,<ref>{{Cite journal |last1=Motani |first1=Ryosuke |last2=Ji |first2=Cheng |last3=Tomita |first3=Taketeru |last4=Kelley |first4=Neil |last5=Maxwell |first5=Erin |last6=Jiang |first6=Da-yong |last7=Sander |first7=Paul Martin |date=2013-12-11 |editor-last=Dodson |editor-first=Peter |title=Absence of Suction Feeding Ichthyosaurs and Its Implications for Triassic Mesopelagic Paleoecology |journal=PLOS ONE |language=en |volume=8 |issue=12 |article-number=e66075 |doi=10.1371/journal.pone.0066075 |doi-access=free |issn=1932-6203 |pmc=3859474 |pmid=24348983|bibcode=2013PLoSO...866075M }}</ref> using the jaws and teeth alone to capture prey. ''Ichthyosaurus'' is thought to have been a pursuit predator that was capable of sustained swift swimming via thunniform locomotion.<ref>{{Cite journal |last1=Dick |first1=Daniel G. |last2=Maxwell |first2=Erin E. |date=July 2015 |title=The evolution and extinction of the ichthyosaurs from the perspective of quantitative ecospace modelling |journal=Biology Letters |language=en |volume=11 |issue=7 |article-number=20150339 |doi=10.1098/rsbl.2015.0339 |issn=1744-9561 |pmc=4528449 |pmid=26156130}}</ref> Stomach contents of ''Ichthyosaurus anningae'' indicate that it fed on cephalopods (likely belemnites) and fish.<ref>D.R. Lomax [https://paludicolavertpaleo.files.wordpress.com/2018/05/8-1-lomax-2010.pdf An ''Ichthyosaurus'' (Reptilia: Ichthyosauria) with gastric contents from Charmouth, England: first report of the genus from the Pliensbachian] Paludicola, 8 (2010), pp. 23-36</ref> Like other ichthyosaurs, it likely relied on its sense of sight, possibly in combination with olfaction.<ref>{{Cite journal |last1=Müller |first1=Johannes |last2=Bickelmann |first2=Constanze |last3=Sobral |first3=Gabriela |date=2018-05-30 |title=The Evolution and Fossil History of Sensory Perception in Amniote Vertebrates |url=https://www.annualreviews.org/doi/10.1146/annurev-earth-082517-010120 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=46 |issue=1 |pages=495–519 |doi=10.1146/annurev-earth-082517-010120 |bibcode=2018AREPS..46..495M |issn=0084-6597|url-access=subscription }}</ref>
It was initially believed that ''Ichthyosaurus'' laid eggs on land, but fossil evidence shows that in fact the females gave birth to live young. As such, they were well-adapted to life as fully pelagic organisms (i.e. they never came onto land). Three pregnant females are known, all of the subspecies ''I. somersetensis.'' Although none of the fetuses show a clear birth orientation it is likely they exited tail-first, a common feature in highly aquatic vertebrates.<ref name="Böttcher, 1990"/>
== Cultural significance == [[File:View of a dinosaur in the Dinosaur Trail in Crystal Palace Park ^19 - geograph.org.uk - 4491074.jpg|thumb|right|Historically important sculpture of ''Ichthyosaurus communis'' (left) in Crystal Palace Park]] Joseph Scheffels's poem ''Der Ichthyosaurus'' describes its extinction in humouristic verses. A monument on Hohentwiel cites it as well.<ref>[http://www.siecke.com/R_SIECKE_katalog_innen_opt.pdf Werkkatalog Sieckes] (PDF; 7,7 MB)</ref> The poem has been translated among others by Charles Leland.<ref>Charles Godfrey Leland, Gaudeamus! Humorous Poems by Joseph Viktor von Scheffel, [http://www.gutenberg.org/ebooks/35848?msg=welcome_stranger#bibrec Ebook-Nr. 35848 on gutenberg.org]</ref> Some of the stanzas: {{Quote box2 |width=320px |border=1px |align=center |bgcolor=#ffe4b5 |fontsize=100% |halign=center |quote=<poem> The rushes are strangely rustling, The ocean uncannily gleams, As with tears in his eyes down gushing, An Ichthyosaurus swims.
He bewails the frightful corruption Of his age, for an awful tone Has lately been noticed by many In the Lias formation shown. </poem>}} {{Clear}}
==See also== * List of ichthyosaurs * Timeline of ichthyosaur research
==References== {{Reflist}}
{{Ichthyosauria|Parvipelvia}} {{Taxonbar|from=Q131565}}
Category:Ichthyosaurs of Europe Category:Early Jurassic ichthyosaurs Category:Early Jurassic reptiles of Europe Category:Late Triassic ichthyosaurs Category:Late Triassic reptiles of Europe Category:Fossil taxa described in 1821 Category:Rhaetian first appearances Category:Taxa named by Henry De la Beche Category:Taxa named by William Conybeare Category:Early Jurassic genus first appearances Category:Early Jurassic genus extinctions Category:Ichthyosauromorph genera