Phylogeny of "Fish"

The term "fish" is often used for any any swimming vertebrate with fins. This includes agnathous lampreys & hagfish, the extinct class Placoderma, and the class Chondricthyes (sharks & rays). As a taxonomic class, Osteichthyes is 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 Actionopterygia is a clade.

Text material © 2002 by Steven M. Carr