The Perciformes is the largest and most diverse group of modern bony fish, comprising about 40% of bony fish. The order is difficult to define as the members do not share a single character or a unique combination of characters. Perciform fish share a number of characters and all lack a number of characters. Many species have a generalized perch-like body shape. All have the following characters: dorsal, anal and pelvic fins with fin spines; Pelvic fins with a spine and up to 5 rays, usually positioned forward on the body; 17 or fewer major caudal rays that articulate with up to five boneshipurals; Four gill arches; 7 or fewer branchiostegal rays and lack an adipose fin.
They are also called Percomorpha or Acanthopteri. They belong to the class of striped-finned fish, and comprise more than 10,000 species that are found in almost all aquatic ecosystems. The order contains approximately 160 families, which is the largest part of any order within vertebrates. It is also the most variable size order of vertebrates, ranging from the 7-mm (1/4-in) Schindleria brevipinguis to the marlin in the genus Makaira. They appeared and diversified for the first time in the Upper Cretaceous.
Among the best known members of this group are the cichlids, California lamb heads, blue worms, plungers, snappers, bass, and perch.
The dorsal and anal fins are divided into anterior spinous portions and posterior soft rays, which may be partially or totally separated. Pelvic fins typically have a spine and up to five smooth rays, placed unusually forward under the chin or under the belly. The scales are usually ctenoid, although they are sometimes cycloid or otherwise modified.
The classification is controversial, Perciformes are almost certainly paraphyletic. Other orders that should possibly be included as suborders are Scorpaeniformes, Tetraodontiformes, and Pleuronectiformes. Of the currently recognized suborders, several may be paraphyletic, as well. These are grouped by suborder / superfamily, generally following the text Fish of the World.
