Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs," although the term is also used for wider clades that the order resides in.
Ichthyopterygia was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitive early and middle Triassic ancestors.
Shonisaurus is a genus of very large ichthyosaurs. At least 37 incomplete fossil specimens of the marine reptile have been found in the Luning Formation of Nevada, USA. This formation dates to the late Carnian age of the late Triassic period, about 237–227 million years ago.
Cymbospondylus is an extinct genus of large ichthyosaurs, of which it is among the oldest representatives, that lived during the Anisian stage of the Middle Triassic in what are now North America and Europe. The first known fossils of this taxon are a set of more or less complete vertebrae which were discovered in the 19th century in various mountain ranges of Nevada, in the United States, before being named and described by Joseph Leidy in 1868. It is in the beginning of the 20th century that more complete fossils were discovered through several expeditions launched by the University of California, and described in more detail by John Campbell Merriam in 1908, thus visualizing the overall anatomy of the animal. While many species have been assigned to the genus, only five are recognized as valid, the others being considered synonymous, doubtful or belonging to other genera. Cymbospondylus was formerly classified as a representative of the Shastasauridae, but more recent studies consider it to be more basal, view as the type genus of the Cymbospondylidae.
Mixosaurus is an extinct genus of Middle Triassic ichthyosaur. Its fossils have been found near the Italy–Switzerland border and in South China.
Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period. It was nearly 2.5–3 metres (8.2–9.8 ft) long with a slender body. The first specimen was found in Utatsu-cho, Miyagi Prefecture, Japan. It is the only described species in the genus Utatsusaurus and the only member of the family Utatsusauridae. The name Utatsusaurus was given after the city. The fossils have been found from the Early Triassic Osawa Formation of Miyagi Prefecture, Japan and British Columbia, Canada.
Shastasauridae is an extinct family of Triassic ichthyosaurs that includes the genera Shastasaurus, Shonisaurus and Himalayasaurus. Many other Triassic ichthyosaurs have been assigned to Shastasauridae in the past, but recent phylogenetic analyses suggest that these species form an evolutionary grade of early ichthyosaurs rather than a true clade or evolutionary grouping that can be called Shastasauridae.
Chaohusaurus is an extinct genus of basal ichthyopterygian, depending on definition possibly ichthyosaur, from the Early Triassic of Chaohu and Yuanan, China.
Grippia is a genus of early ichthyopterygian, an extinct group of reptiles that resembled dolphins. Its only species is Grippia longirostris. It was a relatively small ichthyopterygian, measuring around 1–1.5 metres (3.3–4.9 ft) long. Fossil remains from Svalbard from the specimen SVT 203 were originally assigned to G. longirostris but are now thought to have belonged to a non-ichthyopterygian diapsid related to Helveticosaurus.
Callawayia is an extinct genus of ichthyosaur. It contains the species Callawayia neoscapularis.
Hudsonelpidia is an extinct genus of small parvipelvian ichthyosaur known from British Columbia of Canada.
Thaisaurus is an extinct genus of ichthyopterygian marine reptile that lived during the Spathian. Fossils have been found in Thailand.
Toretocnemus is an extinct genus of ichthyosaur. Its remains have been found in California, United States, in Triassic layers of the Carnian Hosselkus Limestone.
Wimanius is a genus of ichthyosaur from the Middle Triassic of Switzerland, containing a single species, Wimanius odontopalatus. It was described by Michael Maisch and Andreas Matzke in 1998 based on an incomplete skull from Monte San Giorgio, a mountain on the Swiss-Italian border. Wimanius possesses teeth on its palate, though whether they were located on the palatine or pterygoid is disputed. Other features of Wimanius include a large orbit and jugals with two rami of similar lengths. Different phylogenetic placements of Wimanius have been recovered by different studies, including it being a mixosaurid relative or a merriamosaur, and a monotypic family, Wimaniidae has been named for it. However, its validity has also been questioned, and synonymy with various other genera has been proposed.
Mixosauridae was an early group of ichthyosaurs, living between 247.2 and 235 million years ago, during the Triassic period. Fossils of mixosaurs have been found all over the world: China, Timor, Indonesia, Italy, Germany, Spitsbergen, Switzerland, Svalbard, Canada, Alaska, and Nevada.
Thunnosauria is an extinct clade of parvipelvian ichthyosaurs from the Early Jurassic to the early Late Cretaceous (Hettangian–Cenomanian) of Asia, Australia, Europe, North America, and South America. Named by Ryosuke Motani in 1999, it contains the basal taxa Ichthyosaurus and Stenopterygius and the family Ophthalmosauridae. In thunnosaurs, the fore fin is at least twice as long as the hind fin.
Macgowania is an extinct genus of parvipelvian ichthyosaur known from British Columbia of Canada.
Parvipelvia is an extinct clade of euichthyosaur ichthyosaurs that existed from the Late Triassic to the early Late Cretaceous of Asia, Australia, Europe, North America and South America. Named by Ryosuke Motani, in 1999, it contains the basal taxa like Macgowania and Hudsonelpidia. Maisch and Matzke (2000) found in their analysis seven synapomorphies that support Parvipelvia. They also found 10 synapomorphies that support the existence of post-Triassic clade of ichthyosaurs, for which the name Neoichthyosauria was found to be available. Parvipelvians were the only ichthyosaurs to survive the Triassic-Jurassic extinction event.
Thalattoarchon is an extinct genus of large predatory ichthyosaurs that lived during the Anisian stage of the Middle Triassic in what is now North America. The only known species is T. saurophagis, described in 2013 from a single specimen discovered in the Favret Formation, Nevada. The generic name, meaning "ruler of the seas", refers to its status as an apex predator, while the specific epithet, meaning "lizard eater", alludes to its carnivorous diet. The classification of this genus within the ichthyosaurs is much debated, being either classified within the clade Merriamosauria or in the more basal family Cymbospondylidae.
