See text for orders.
The Actinopterygii are the ray-finned fish. They are the dominant group of vertebrates, with over 27,000 species ubiquitous throughout fresh water and marine environments.
Traditionally three grades of Actinopterygii have been recognized: the Chondrostei, Holostei, and Teleostei. The second is paraphyletic and tends to be abandoned, however, while the first is now restricted to those forms closer to extant Chondrostei than to the other groups. Nearly all fish alive today are teleosts.
A listing of the different groups is given below, down to the level of orders, arranged in what is believed to represent the evolutionary sequence down to the level of superorder. The listing follows FishBase with notes when this differs from Nelson and ITIS.
- Subclass Chondrostei
- Order Lepisosteiformes, the gars
- Order Amiiformes, the bowfins
- Superorder Osteoglossomorpha
- Order Elopiformes, including the
ladyfishes and tarpon
Order Albuliformes, the bonefishes
Order Notacanthiformes, including the halosaurs and spiny eels
Order Anguilliformes, the true eels and gulpers
Order Saccopharyngiformes, including the gulper eel
- Order Elopiformes, including the ladyfishes and tarpon
- Order Clupeiformes, including herrings and anchovies
- Order Gonorynchiformes, including the
Order Cypriniformes, including barbs, carp, danios, goldfishes, loaches, minnows, rasboras
Order Characiformes, including characins, pencilfishes, hatchetfishes, piranhas, tetras.
Order Gymnotiformes, including electric eels and knifefishes
Order Siluriformes, the catfishes
- Order Gonorynchiformes, including the milkfishes
- Order Salmoniformes, including salmon
Order Esociformes the pike
Order Osmeriformes, including the smelts and galaxiids
- Order Salmoniformes, including salmon and trout
- Order Ateleopodiformes, the jellynose
Order Stomiiformes, including the bristlemouths and marine hatchetfishes
- Order Ateleopodiformes, the jellynose fish
- Order Aulopiformes, including the Bombay duck and lancetfishes
- Order Myctophiformes, including the lanternfishes
- Order Lampriformes, including the oarfish, opah and ribbonfishes
- Order Polymixiiformes, the beardfishes
- Order Percopsiformes, including the
cavefishes and trout-perches
Order Batrachoidiformes, the toadfishes
Order Lophiiformes, including the anglerfishes
Order Gadiformes, including cods
Order Ophidiiformes, including the pearlfishes
- Order Percopsiformes, including the cavefishes and trout-perches
- Order Mugiliformes, the mullets
Order Atheriniformes, including silversides and rainbowfishes
Order Beloniformes, including the flyingfishes
Order Cetomimiformes, the whalefishes
Order Cyprinodontiformes, including livebearers, killifishes
Order Stephanoberyciformes, including the ridgeheads
Order Beryciformes, including the fangtooths and pineconefishes
Order Zeiformes, including the dories
Order Gobiesociformes, the clingfishes
Order Gasterosteiformes including sticklebacks, pipefishes, seahorses
Order Syngnathiformes, including the seahorses and pipefishes 
Order Synbranchiformes, including the swamp eels
Order Tetraodontiformes, including the filefishes and pufferfish
Order Pleuronectiformes, the flatfishes
Order Scorpaeniformes, including scorpionfishes and the weaver fish
Order Perciformes 40% of all fish including anabantids, bass, cichlids, gobies, gouramis, mackerel, perches, scats, whiting, wrasses
- Order Mugiliformes, the mullets
- Infraclass Holostei
- ^ R. Froese and D. Pauly (editors) (February 2006). FishBase.
- ^ Joseph S. Nelson. Fishes of the World. John Wiley & Sons. ISBN 0-471-54713-1.
- ^ Actinopterygii (TSN 161061). Integrated Taxonomic Information System. Accessed on 3 April 2006.
- ^ In ITIS, Gobiesociformes is placed as the suborder Gobiesocoidei of the order Perciformes.
- ^ In ITIS, Syngnathiformes is placed as the suborder Syngnathoidei of the order Gasterosteiformes.