Belongs within: Neodiapsida.
Contains: Hueneosauria.
The Ichthyosauria are a major clade of marine reptiles known from the Lower Triassic to the lower Upper Cretaceous, members of which evolved a remarkably fish-like body form (Maisch & Matzke 2000).
Characters (from Maisch & Matzke 2000): Premaxillary rostrum elongate; naris displaced posteriorly, close to orbit; upper temporal fenestra with very considerable contribution of supratemporal; ectopterygoid absent; thoracal ribs articulating exclusively with centrum; manus and pes exhibiting hyperphalangy; fibula immobile relative to femur.
<==Ichthyosauria [Eoichthyosauria, Ichthyopterygia] |--Thaisaurus Mazin, Suteethorn et al. 1991MM03 | `--*T. chonglakmanii Mazin, Suteethorn et al. 1991MM00 `--+--Parvinatator Nicholls & Brinkman 1995FF13, MM03 | `--*P. wapitiensis Nicholls & Brickman 1995MM00 `--+--Utatsusaurus Shikama, Kamei & Murata 1978FF13, MM03 | `--*U. hataii Shikama, Kamei & Murata 1978MM00 `--+--+--HueneosauriaFF13 | `--Quasianosteosaurus Maisch & Matzke 2003 [Quasianosteosauridae]MM03 | `--*Q. vikinghoegdai Maisch & Matzke 2003MM03 `--Grippiidae [Grippidia]MM00 |--Chaohusaurus Young & Dong 1972MM03 (see below for synonymy) | `--*C. geishanensis Young & Dong 1972MM00 `--Grippia Wiman 1929FF13, MM03 `--*G. longirostris Wiman 1929MM00 Ichthyosauria incertae sedis: Isfjordosaurus Motani 1999MM03 `--*I. minor (Wiman 1910) [=Pessopteryx minor]MM00 Svalbardosaurus Mazin 1981 (n. d.)MM03 `--S. crassidens Mazin 1981B93 Himalayasaurus Young & Dong 1972 (n. d.)MM00 `--*H. tibetensis Young & Dong 1972 (n. d.)MM00 Tibetosaurus Dong in Young et al. 1982 (n. d.)MM00 `--*T. tingjiensis Dong in Young et al. 1982 (n. d.)MM00 Pessosaurus Wiman 1910 (n. d.)MM00 |--*P. polaris (Hulke 1873) (n. d.)MM00 `--P. suevicus von Huene 1916MM00 Macropterygius von Huene 1922 (n. d.)MM00 `--*M. trigonus (Owen 1840)MM00 Pachygonosaurus von Huene 1916 (n. d.)MM00 `--*P. robustus Maisch & Matzke 1997 (n. d.)MM00 OmphalosauridaeH02 |--Tholodus schmidiH02 `--Omphalosaurus Merriam 1906D07 [incl. Pessopteryx Wiman 1910MM00] |--O. nettarhynchus Mazin & Bucher 1987B93 |--O. nevadanus Merriam 1906MM00 |--O. nisseri (Wiman 1910) (see below for synonymy)MM00 `--O. wolfiD07
Chaohusaurus Young & Dong 1972MM03 [incl. Anhuisaurus Chen 1985 (preoc.)MM00, Chensaurus Mazin, Suteethorn et al. 1991MM00]
Omphalosaurus nisseri (Wiman 1910) [=*Pessopteryx nisseri; incl. P. arctica Wiman 1910, P. pinguis Wiman 1910]MM00
*Type species of generic name indicated
References
[B93] Benton, M. J. 1993. Reptilia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 681–715. Chapman & Hall: London.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[FF13] Fröbisch, N. B., J. Fröbisch, P. M. Sander, L. Schmitz & O. Rieppel. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. Proceedings of the National Academy of Sciences of the USA 110 (4): 1393–1397.
[H02] Haubold, H. 2002. Literaturbericht: Ichthyosaurier und Sauropterygier. Zbl. Geol. Paläont. Teil II 5-6: 367–403.
[MM00] Maisch, M. W., & A. T. Matzke. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298: 1–159.
[MM03] Maisch, M. W., & A. T. Matzke. 2003. Observations on Triassic ichthyosaurs. Part XII. A new Early Triassic ichthyosaur genus from Spitzbergen. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 229 (3): 317–338.