Teleostei

(vertebrate zoology) An infraclass of the subclass Actinopterygii, or rayfin fishes; distinguished by paired bracing bones in the supporting skeleton of the caudal fin, a homocercal caudal fin, thin cycloid scales, and a swim bladder with a hydrostatic function.

The largest, youngest (first appearing in the Upper Triassic), and most successful group of the actinopterygians (rayfin fishes), and a sister group of the Amiidae (bow fins). The 23,600 species of teleosts make up more than half of all recognized species of living vertebrates, and over 96% of all living fish species. There are 494 families, of which 69 are extinct leaving 425 extant families, 43% of which have no fossil record. See also Actinopterygii; Amiiformes.

Much of the evidence for teleost monophyly and relationships comes from the caudal skeleton and concomitant acquisition of a homocercal tail (upper and lower lobes symmetrical). Other characters of the teleosts include the mobile premaxilla bone, the extension of the posterior myodome (the eye muscle canal) into the basioccipital bone, and the development of the swim bladder. See also Swim bladder.

The Osteoglossomorpha, Elopomorpha, and Clupeomorpha are now generally regarded as successive clades (groups) above the level of the fossil, paraphyletic pholidophorids. The Clupeomorpha is considered to be the sister group of the Ostariophysi.

Clupeomorpha and Ostariophysi

The Clupeomorpha includes almost 80 genera and some 360 Recent species in three main families: Engraulidae (anchovies), Dussumieridae (round herrings), Clupeidae (herrings), as well as Pristigasteridae. The Ostariophysi make up nearly 75% of the fresh-water fishes of the world (over 6000 species) and include the Cypriniformes (carps, loaches, and relatives), Siluriformes (catfishes), Gymnotiformes (knife fishes, electric eel), and Chanos. The Clupeomorpha plus Ostariophysi are the sister group of the Euteleostei. See also Cypriniformes; Osteoglossiformes; Pholidophoriformes.

Euteleostei

The Euteleostei are by far the largest teleost taxon with more than 22,000 species arranged in some 340 families. They comprise two major lineages, the Protacanthopterygii and the Neognathi.

The Protacanthopterygii (often regarded as lower euteleosteans) include four groups: the salmonoids (salmon and allies; 66 species) and the osmeroids (smelts, salangrids, Lepidogalaxius; 72 species), which together are the sister group of the alepocephaloids (slickheads; 60+ species) plus the argentinoids (argentines or herring smelts; 60+ species). The Neognathi, on the other hand, are made up of the esocoids (pike and mudminnows; 10+ species) plus the sister group Neoteleostei. See also Salmoniformes.

The Neoteleostei, with more than 15,319 species, comprise four main clades, the Stomiiformes, Aulopiformes, Myctophiformes, and Acanthomorpha (paracanthopterygians plus acanthopterygians). The acanthopterygians are the largest subgroup of the Euteleostei, distributed among 12 orders and 218 families. The Perciformes form the largest of these orders with 9293 species. See also Perciformes.