neoteleost

Neoteleostei is a clade of ray-finned fishes that forms one of the major lineages within the Teleostei, the largest group of living vertebrates. The name, meaning "new true teleosts," contrasts with earlier-diverging euteleost lineages. In contemporary classifications, Neoteleostei is part of Euteleostei and comprises the majority of extant teleost diversity, including many orders and families that dominate modern freshwater and marine ecosystems. The group is defined more by molecular phylogenies than by a single, universal morphological synapomorphy; as a result, its exact composition has fluctuated with new data, but consensus supports a monophyletic crown group.

Fossil records show Neoteleostei first appearing in the Early Cretaceous, with substantial diversification through the Late Cretaceous and Cenozoic. Today, neoteleosts occupy almost every aquatic habitat, from open oceans to rivers, and include many economically important species. The clade is important for studies of vertebrate evolution because its members display a wide range of body plans, reproductive strategies, and feeding ecologies that illuminate patterns of adaptation in teleosts.

Taxonomic placement remains an area of active research; while broad consensus identifies Neoteleostei as a major crown group within Teleostei, the internal branching order is still refined as new molecular and morphological data become available. Overall, Neoteleostei represents the most species-rich and ecologically diverse portion of the teleost fishes, reflecting extensive evolutionary success since the Early Cretaceous.