Perciformes

Perciformes, also called the Acanthopteri, is an order or superorder of ray-finned fish in the clade Percomorpha. Perciformes means "perch-like". Among the well-known members of this group are perch and darters (Percidae), sea bass and groupers (Serranidae).

Taxonomy
Formerly, this group was thought to be even more diverse than it is thought to be now, containing about 41% of all bony fish (about 10,000 species) and about 160 families, which is the most of any order within the vertebrates. However, many of these other families have since been reclassified within their own orders within the clade Percomorpha, significantly reducing the size of the group. In contrast to this splitting, other groups formerly considered distinct, such as the Scorpaeniformes, are now classified in the Perciformes.

Evolution
The earliest fossil perciform is the extinct serranid Paleoserranus from the Early Paleocene of Mexico, but potential records of "percoids" are known from the Maastrichtian, including Eoserranus, Indiaichthys, and Prolates, although their exact taxonomic identity remains uncertain.

Characteristics
The dorsal and anal fins are divided into anterior spiny and posterior 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 to the touch), although sometimes they are cycloid (smooth to the touch) or otherwise modified.

Taxonomy
Classification of this group is controversial. As traditionally defined before the introduction of cladistics, the Perciformes are almost certainly paraphyletic. Other orders that should possibly be included as suborders are the Scorpaeniformes, Tetraodontiformes, and Pleuronectiformes. Of the presently recognized suborders, several may be paraphyletic, as well. These are grouped by suborder/superfamily, generally following the text Fishes of the World.