Actinopterygii, members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of skin supported by radially extended thin bony spines called lepidotrichia, as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii. Resembling folding fans, the actinopterygian fins can easily change shape and wetted area, providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the articulation between these fins and the internal skeleton.
The Amiiformes order of fish has only two extant species, the bowfins: Amia calva and Amia ocellicauda, the latter recognized as a separate species in 2022. These Amiiformes are found in the freshwater systems of North America, in the United States and parts of southern Canada. They live in freshwater streams, rivers, and swamps. The order first appeared in the Triassic, and the extinct members include both marine and freshwater species, many of which are morphologically disparate from bowfins, such as the caturids.
Chondrostei is a group of non-neopterygian ray-finned fish. While the term originally referred to the paraphyletic grouping of all non-neopterygian ray-finned fish, it was redefined by Patterson in 1982 to be a clade comprising the Acipenseriformes and their extinct relatives.
Neopterygii is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast majority of extant fishes, and over half of all living vertebrate species. While living holosteans include only freshwater taxa, teleosts are diverse in both freshwater and marine environments. Many new species of teleosts are scientifically described each year.
Dapedium is an extinct genus of primitive marine neopterygian ray-finned fish. The first-described finding was an example of D. politum, found in the Lower Lias of Lyme Regis, on the Jurassic Coast of England. Dapedium lived in the Late Triassic to the Middle Jurassic period, from the late Norian to the early Aalenian.
Saurichthys is an extinct genus of predatory ray-finned fish from the Triassic Period. It is the type genus of the family Saurichthyidae, and the most speciose and longest lasting genus in the family. This family also includes the Permian Eosaurichthys (China) and the Jurassic Saurorhynchus from Europe and North America, though it may be more appropriate to treat these as subgenera of Saurichthys, due to the genus Saurichthys otherwise being paraphyletic.
Birgeria is a genus of carnivorous marine ray-finned fish from the Triassic period. Birgeria had a global distribution, with fossil known from Madagascar, Spitsbergen, Germany, Switzerland, Italy, Slovenia, China, Russia, Canada and Nevada, United States. The oldest fossils are from Griesbachian aged beds of the Wordie Creek Formation of East Greenland. Birgeria existed throughout the entire Triassic period, from the very beginning just after the Permian-Triassic mass extinction, up to the very end with its extinction during the Triassic-Jurassic mass extinction.
Pycnodontiformes is an extinct order of primarily marine bony fish. The group first appeared during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America.
Daedalichthys is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Early Triassic epoch. It contains a single species, D. formosa from the Olenekian-aged Cynognathus Assemblage Zone of South Africa. It was previously classified in Dictyopyge.
Brookvalia is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Middle Triassic epoch.
Ctenognathichthys is an extinct genus of prehistoric marine ray-finned fish that lived during the Middle Triassic epoch of Europe, in the former Tethys Ocean.
Acentrophorus is an extinct genus of prehistoric freshwater and marine ray-finned fish from the Roadian to the Wuchiapingian of England, Germany (Kupferschiefer), Italy and Russia. There may also be a Triassic occurrence in Australia.
Dipteronotus is an extinct genus of stem-neopterygian ray-finned fish that existed during the Middle and Late Triassic epochs in what is now Europe and Morocco. As a typical feature, it had several ridge scales in front of its dorsal fin that created a spine-like structure.
Saurichthyiformes is an extinct order of ray-finned fish which existed in Asia, Africa, Australia, Europe and North America, during the late Permian to early Middle Jurassic. Saurichthyiiformes comprise two families, Saurichthyidae and Yelangichthyidae. Yelangichthyidae is monotypic, containing only the genus Yelangichthys. The gar or needlefish-like Saurichthyidae is primarily known from the genus Saurichthys. Additionally, the subgenera SaurorhynchusCostasaurichthys, Eosaurichthys, Lepidosaurichthys, and Sinosaurichthys are frequently used to group species, and are sometimes considered separate genera. Species are known from both marine end freshwater deposits. They had their highest diversity during the Early and Middle Triassic. Their phylogenetic position is uncertain, while they have often been considered members of Chondrostei, and thus related to living sturgeons and paddlefish, phylogenetic analysis of well-preserved remains has considered this relationship equivocal. They may actually belong to the stem-group of Actinopterygii, and thus not closely related to any living group of ray-finned fish.
Ptycholepiformes are an extinct order of prehistoric ray-finned fish that existed during the Triassic period and the Early Jurassic epoch. The order includes the genera Acrorhabdus, Ardoreosomus, Boreosomus, Chungkingichthys, Ptycholepis, and Yuchoulepis. Although several families have been proposed, some studies place all these genera in the same family, Ptycholepididae.
Dorsetichthys is an extinct genus of stem-teleost ray-finned fish from the Early Jurassic period of Europe.
Ginglymodi is a clade of ray-finned fish containing modern-day gars (Lepisosteidae) & their extinct relatives in the order Lepisosteiformes, the extinct orders Semionotiformes and Kyphosichthyiformes, and various other extinct taxa. Ginglymodi is one of the two major subgroups of the infraclass Holostei, the other one being Halecomorphi, which contains the bowfin and eyespot bowfin and their fossil relatives.
Dapediidae is an extinct family of neopterygian ray-finned fish that lived from the Middle Triassic to Late Jurassic. It is the only family of the order Dapediiformes. Its members were historically placed within the ginglymodian family Semionotidae, but were moved to their own family in 1966.
Marcopoloichthys is an extinct genus of marine teleosteomorph ray-finned fish known from the Middle and Late Triassic of the former Tethys Ocean. It is the only genus in the family Marcopoloichthyidae. It was originally described based on specimens from both Italy and China, hence the name Marcopoloichthys, which references the medieval Venetian merchant Marco Polo, who traveled from Italy to China.
Redfieldius is an extinct genus of freshwater ray-finned fish that inhabited eastern North America during the Early Jurassic period. It contains a single species, R. gracilis, known from the Hettangian to the Sinemurian of the northeastern United States. It is the type genus and was the last surviving member of the order Redfieldiiformes, which was widespread and diverse throughout the preceding Triassic period. It is notable for representing possibly the first fossil bony fish collected from North America, with a specimen from Middletown collected in 1816 by Benjamin Silliman.
