Perciformes

The Perciformes also called the Percomorphi or Acanthopteri is the largest order of vertebrates. They have about 40% of all bony fish.Long, John A. 1995. The rise of fishes: 500 million years of evolution. Johns Hopkins University Press, Baltimore.p151  

Perciformes means perch-like. They belong to the class of ray-finned fish and have over 7,000 species in almost all aquatic environments.

They have the widest range of sizes of any order of vertebrates, ranging from the 7 mm Schindleria brevipinguis to the 5 metre Makaira species. They first appeared and diversified in the Upper Cretaceous.

Some well-known members of this group are angelfish, barracuda, bass, blenny, cichlids, damselfish, filefish, goby, grouper, remora, swordfish, mackerel, pufferfish, tilefish, tuna, whiting, and of course perch.

Characteristics

The dorsal and anal fins are divided into front spiny and back soft-rayed portions, which may be partially or completely separated. 

The pelvic fins usually have one spine and up to five soft rays, positioned unusually far forward under the chin or under the belly. Scales are usually ctenoid (rough-edged). 

Taxonomy
They are grouped as in the text Fishes of the World. The order is probably polyphyletic, and changes may occur in this and other teleost orders.

Recent morphological and DNA sequence analysis has shown that several of the higher-level groupings of teleosts are evolutionary grades rather than clades. Examples of demonstrably paraphyletic groups include the Perciformes.G.D. Johnson and E.O. Wiley 2006. Tree of life: Percomorpha

 References