Evolution & Phylogeny of "Fish"

The term "fish" is often used for any any swimming vertebrate with fins. Broadly, this includes jawless (agnathous) lampreys & hagfish, the extinct class Placoderma, and the class Chondricthyes (sharks & rays). As a taxonomic class, Osteichthyes was used for bony fish, including the "ray-finned" Actinopterygia that include more than 99% of modern fish diversity, as well as "fleshy-finned" lungfish & coelacanths, whose anatomy more closely resembles that of their terrestrial descendants (Tetrapoda). Exclusion of tetrapods makes Osteichthyes a grade classification: note that Actinopterygia is a clade.