Ichthyosaurus communis

''Ichthyosaurus'' (derived from Greek ' () meaning 'fish' and ' () meaning 'lizard') is a genus of ichthyosaurs from the Early Jurassic (Hettangian - Pliensbachian), with possible Late Triassic record, from Europe (Belgium, England, Germany, Switzerland, and Portugal). It is among the best known ichthyosaur genera, as it is the type genus of the order Ichthyosauria.Maisch MW, Matzke AT. 2000. The Ichthyosauria. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' 298: 1-159McGowan 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; MünchenMaisch MW, Reisdorf AG, Schlatter R, Wetzel A. 2008. A large skull of Ichthyosaurus (Reptilia: Ichthyosauria) from the Lower Sinemurian (Lower Jurassic) of Frick (NW Switzerland). ''Swiss Journal of Geosciences'' 101: 617-627.

History of discovery

''Ichthyosaurus'' was the first complete fossil to be discovered in the early 19th century by Mary Anning in England; the holotype of ''I. communis'', no coll. number given, was a fairly complete specimen discovered by Mary and Joseph Anning around 1814 in Lyme Regis but was reported as lost by McGowan (1974) in his review of the latipinnate ichthyosaurs of England. The name ''Ichthyosaurus'' was first used by Charles König 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 De la 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 1811-12. 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.

''I. anningae'', described in 2015 from a fossil found in the early 1980s in Dorset, England, was named after Anning. 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.

Description

''Ichthyosaurus'' was smaller than most of its relatives, with the largest specimen of ''I. somersetensis'' measuring up to in length and in body mass. In comparison, other species were much smaller. ''I. communis'' and ''I. larkini'' measured up to in length and in body mass, while ''I. conybeari'' measured up to in length and in body mass. 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.Böttcher R. 1990. Neue Erkenntnisse über die Fortpflanzungsbiologie der Ichthyosaurier. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' 164: 1-51Martill 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 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.

Classification

This cladogram below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell.

Palaeobiology

''Ichthyosaurus'' ear bones were solid, probably transferring water vibrations to the inner ear. Even so, anatomical features demonstrate that it was a visually-oriented predator; it had huge, sensitive eyes, protected by bony shields. Coprolites of ''Ichthyosaurus'' reveal that its diet consisted of fish and squid.

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). The babies were born tail first to prevent them from drowning in the water.

Cultural significance

Joseph Victor von Scheffels poem ''Der Ichthyosaurus'' describes its extinction in humouristic verses. A monument on Hohentwiel cites it as well. The poem has been translated among others by Charles Godfrey LelandCharles Godfrey Leland, Gaudeamus! Humorous Poems by Joseph Viktor von Scheffel
Ebook-Nr. 35848 on gutenberg.org
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Some of the stanzas:

See also

* List of ichthyosaurs
* Timeline of ichthyosaur research

References

{{Taxonbar, from=Q131565

Ichthyosaurs of Europe
Early Jurassic ichthyosaurs
Early Jurassic reptiles of Europe
Late Triassic ichthyosaurs
Late Triassic reptiles of Europe
Fossil taxa described in 1821
Rhaetian first appearances
Taxa named by Henry De la Beche
Taxa named by William Conybeare
Early Jurassic extinctions
Ichthyosauromorph genera