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 perches and darters, and also sea basses and groupers. This order contains many familiar freshwater temperate and tropical marine fish groups, but also extremophiles that have successfully colonized both the North and South Poles, as well as the deepest depths of the ocean.

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 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 stem group-perciform Paleoserranus from the Early Paleocene of Mexico, but potential records of "percoids" are known from the Maastrichtian, including Eoserranus and Prolates, although their exact taxonomic identity remains uncertain. The earliest crown-group perciform fossils are known from the Early Eocene, including the scorpaenoid Eosynanceja and platycephalid otoliths from New Zealand.

Classification

Classification of this group has long been controversial, with various families being placed in and out of Perciformes depending on the study. Only in recent decades, with the advent of molecular phylogenetics, has the classification of the family been largely resolved. Based on these studies, many suborders formerly placed within the Perciformes are better placed elsewhere in the Percomorpha, but former members of the Scorpaeniformes, Gasterosteiformes, and some members of the Trachiniformes are now considered true perciforms.

Present classification

The following classification is based on Eschmeyer's Catalog of Fishes:
The following fossil families may also belong to Perciformes sensu stricto, although this is uncertain:
  • ?Family †Callipterygidae Jordan, 1905
  • ?Family †Eocottidae Bannikov, 2004
  • ?Family †Robertanniidae Bannikov, 2011
  • Family †Trispinachidae Nazarkin, 2002

    Past classifications

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.

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, although sometimes they are cycloid or otherwise modified.