Chordate Zoology - textbook - Y. V. Tsaryk - 2013

Chapter 4. DIVISION GNATHOSTOMATA, or ECTOBRANCHIATA, GNATHOSTOMATA, seu ECTОBRANCHIATA. SUPERCLASS FISH, PISCES

4.2. CLASS BONY FISHES, OSTEICHTHYES

4.2.3. Systematics of the Class of Bony Fishes and Characteristics of Representatives of Individual Orders

4.2.3.3. Group Teleostei (Teleost Fishes)

As previously mentioned, the remaining ray-finned Fishes are divided into 8-10 superorders. Formerly, they constituted the group of teleost fishes, Teleostei, but today this group is not assigned a specific taxonomic rank on the grounds that the superorders within this group may have descended from different ancestors—bony ganoids. The characteristics of teleosts include: bony scales (some extinct species also possessed ganoid scales); significant Ossification of the neurocranium (the supraoccipital bone is present); a reduced number of bones in the lower jaw (usually three); well-developed bony rays supporting the membranous edge of the operculum; a homocercal caudal fin; the conus arteriosus is shortened and functionally replaced by the bulbus arteriosus; there is no spiral valve in the intestine; and a swim bladder with smooth inner walls, connected by a duct to the dorsal surface of the initial part of the Esophagus (this connection may disappear during ontogeny, and in some species, the swim bladder is secondarily reduced).

Teleost fishes first appeared in the Middle Triassic, and since the Cenozoic era, they have spread globally, giving rise to an extraordinary diversity of forms (representing more than 90% of currently living fish species).