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.

[2] The potentially oldest known neopterygian is the putative "semionotiform" Acentrophorus varians from the Middle Permian of Russia;[3][4] however, one study incorporating morphological data from fossils and molecular data from nuclear and mitochondrial DNA, places this divergence date at least 284 mya (million years ago), during the Artinskian stage of the Early Permian.

[11][13] However, the diversity of the various groups of neopterygians (or of fishes in general) is unevenly distributed, with teleosts making up the vast majority (96%) of living species.

However, a very important step in the evolution of neopterygians is the acquisition of a better control of the movements of both dorsal and anal fins, resulting in an improvement in their swimming capabilities.

All of these characters represented major improvements, resulting in Neopterygii becoming the dominant group of fishes (and, thus, taxonomically of vertebrates in general) today.