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.
Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.
Cypriniformes is an order of ray-finned fish, which includes many families and genera of cyprinid fish, such as barbs, gobies, loaches, botias, and minnows. Cypriniformes is an "order-within-an-order", placed under the superorder Ostariophysi—which is also made up of cyprinid, ostariophysin fishes. The order contains 11–12 families, over 400 genera, and more than 4,250 named species; new species are regularly described, and new genera are recognized frequently. Cyprinids are most diverse in South and Southeast Asia, but are entirely absent from Australia and South America. At 112 years old, the longest-lived cypriniform fish documented is the bigmouth buffalo.
The Gonorynchiformes are an order of ray-finned fish that includes the important food source, the milkfish, and a number of lesser-known types, both marine and freshwater.
Euteleostomi is a successful clade that includes more than 90% of the living species of vertebrates. Both its major subgroups are successful today: Actinopterygii includes most extant bony fish species, and Sarcopterygii includes the tetrapods.
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.
Ostariophysi is the second-largest superorder of fish. Members of this superorder are called ostariophysians. This diverse group contains 10,758 species, about 28% of known fish species in the world and 68% of freshwater species, and are present on all continents except Antarctica. They have a number of common characteristics such as an alarm substance and a Weberian apparatus. Members of this group include fish important to people for food, sport, the aquarium industry, and research.
The Weberian apparatus is an anatomical structure that connects the swim bladder to the auditory system in fishes belonging to the superorder Ostariophysi. When it is fully developed in adult fish, the elements of the apparatus are sometimes collectively referred to as the Weberian ossicles or Weber's ossicles. The presence of the structure is one of the most important and phylogenetically significant distinguishing characteristics of the Ostariophysi. The structure itself consists of a set of minute bones that originate from the first few vertebrae to develop in an embryonic ostariophysan. These bones grow to physically connect the auditory system, specifically the inner ear, to the swim bladder. The structure acts as an amplifier of sound waves that would otherwise be only slightly perceivable by the inner ear structure alone.
The superorder Elopomorpha contains a variety of types of fishes that range from typical silvery-colored species, such as the tarpons and ladyfishes of the Elopiformes and the bonefishes of the Albuliformes, to the long and slender, smooth-bodied eels of the Anguilliformes. The one characteristic uniting this group of fishes is they all have leptocephalus larvae, which are unique to the Elopomorpha. No other fishes have this type of larvae.
Clupeomorpha is a superorder of ray-finned fish which belongs to the clade Otocephala.
Protacanthopterygii is a superorder of ray-finned fish. They inhabit both marine and freshwater habitats. They appear to have evolved in the Cretaceous or perhaps late Jurassic, originating probably roughly 150 million years ago; fossils of them and the closely related Otocephala are known from throughout the Cretaceous.
Acanthomorpha is an extraordinarily diverse taxon of teleost fishes with spiny fin rays. The clade contains about one-third of the world's modern species of vertebrates: over 14,000 species.
Dastilbe is an extinct genus of prehistoric marine & freshwater ray-finned fish from the Early Cretaceous of Brazil. It was a relative of modern milkfish.
Stenopterygii are a superorder of ray-finned fish in the infraclass Teleostei. Their validity is somewhat doubtful, as the group was established to separate, out of a large group of closely related Teleostei, a mere two rather peculiarly autapomorphic orders at best. In some treatments, it is even monotypic.
The Argentiniformes is an order of marine ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the slickheads and allies being the Alepocephaloidei. These suborders were treated as superfamilies Argentinoidea and Alepocephaloidea, respectively, when the present group was still included in the Osmeriformes.
Alepocephaliformes is an order of marine deep-sea teleost fishes. It was previously classified as the suborder Alepocephaloidei of the order Argentiniformes.
The Trachichthyiformes are an order of ray-finned fishes in the superorder Acanthopterygii.
Tselfatiiformes is an extinct order of bony fishes from the infraclass Teleostei. The order represents the most important radiation of marine teleosts during the Cretaceous period. Fossils of tselfatiiforms are known from Europe, North America, central and northern South America, the Middle East and North Africa.
Teleosteomorpha is a clade of ray-finned fishes containing all teleost fish and their closest extinct relatives. Also in this group are two diverse Mesozoic fish orders, the Aspidorhynchiformes and the Pachycormiformes. Several other non-teleostomorph teleosteans existed throughout the Mesozoic, although not as dominant as the two main clades in the group.
