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Actinopterygii

(Class)

Overview

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The Actinopterygii (the plural form of Actinopterygius) constitute the of the ray-finned fishes.

The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).

In terms of numbers, actinopterygians are the dominant class of vertebrates, with nearly 30,000 species, and they are ubiquitous throughout fresh water and marine environments from the deep sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 7.9 mm (0.3 in), to the massive Ocean Sunfish, at 2,300 kg (5,100 lb), and the long-bodied Oarfish, to at least 11 m (36.5 feet).

Fossil Record

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The earliest known fossil Actinopterygiian is Andreolepis hedei, dating back 420 million years (Late Silurian). This microvertebrate has been uncovered in Russia, Sweden, and Estonia[1].

Classification

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Traditionally three grades of actinopterygians have been recognised: the Chondrostei, Holostei, and Teleostei. Some morphological evidence suggests that the second is paraphyletic and should be abandoned; however, recent work based on the analysis of DNA sequence data from the complete mitochondrial genome supports its recognition. Nearly all living bony fishes are teleosts.

A listing of the different groups is given below,down to the level of orders, arranged in what has been suggested to represent the evolutionary sequence down to the level of order based primarily on the long history of morphological studies. This classification, like any other taxonomy based on phylogenetic research is in a state of flux. Many of these ordinal and higher-level groupings have not been supported in both the recent morphological and molecular literature. Examples of demonstrably paraphyletic or unnatural groups include the Paracanthopterygii, Scorpaeniformes, and Perciformes[1]. The listing follows FishBase[2] with notes when this differs from Nelson[3] and ITIS.[4]

Photos

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Taxonomy

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The Class Actinopterygii is further organized into finer groupings including:

Orders

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Acipenseriformes

Acipenseriformes are an of primitive ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families. [more]

Amiiformes

Bowfins are an order (Amiiformes) of primitive . Only one species, the bowfin Amia calva, family Amiidae, exists today, although additional species in six families are known from Jurassic, Cretaceous, and Eocene fossils. These included the huge Leedsichthys, probably the biggest fish that ever existed. The bowfin and the gar are two of the freshwater fishes still extant that existed, almost unchanged from their current form, while the great dinosaurs roamed the earth. [more]

Atheriniformes

Atheriniformes, also known as the silversides, is an of ray-finned fish that includes the Old World silversides and several less-familiar families, including the unusual Phallostethidae. [more]

Aulopiformes

Aulopiformes is an of ray-finned fish consisting of thirteen living families of marine fish. They are grouped together on the strength of common features of pharyngobranchial structure. The common name grinners is sometimes used for this group. [more]

Beloniformes

The Beloniformes are an of five families of freshwater and marine ray-finned fish: the Adrianichthyidae (ricefish and medakas); Belonidae (needlefish); Exocoetidae (flyingfishes); Hemiramphidae (halfbeaks): and the Scomberesocidae (sauries). With the exception of the Adrianichthyidae, these are streamlined, medium-sized fishes that live close to the surface of the water feeding on algae, plankton, or smaller animals including other fishes. Most are marine, though a few needlefish and halfbeaks inhabit brackish and fresh waters. [more]

Beryciformes

Beryciformes is an order of . This is a very poorly understood group of 16 families, 57 genera, and about 219 species. Most believe that it is probably an artificial assemblage of unrelated taxa that are thrown together for convenience only; there are no convincing characters that tie all members together. [more]

Characiformes

The Characiformes are an order of , comprising the characins and their allies. There are a few thousand different species, including the well-known piranha and tetras. [more]

Clupeiformes

Clupeiformes is the order of that includes the herring family, Clupeidae, and the anchovy family, Engraulidae. [more]

Cypriniformes

The Cypriniformes are an of ray-finned fish, including the carps, minnows, loaches and relatives. This order contains 5-6 families, over 320 genera, and more than 3,250 species, with new species being described every few months or so, and new genera being recognized regularly. They are most diverse in southeastern Asia, but are entirely absent from Australia and South America. [more]

Ellimmichthyiformes

[more]

Gadiformes

Gadiformes is an order of , also called the Anacanthini, that includes the cod and its allies. Many major food fish are in this order. [more]

Gasterosteiformes

Gasterosteiformes is an of ray-finned fishes that includes the sticklebacks and relatives. [more]

Gonorhynchiformes

[more]

Ichthyodectiformes

[more]

Lampridiformes

Lampriformes (also spelt Lampridiformes) are an of ray-finned fish that includes about 50 living species of deep sea fishes, including the opahs, crestfishes, ribbonfishes, and oarfish. These are acanthomorph teleosts which diverged at the end of the Cretaceous or in the succeeding Paleocene period, 60-70 million years ago. Their sister order is the Myctophiformes. [more]

Ophidiiformes

Ophidiiformes is an of ray-finned fish that includes the cusk eels (family Ophidiidae), pearlfishes (family Carapidae), brotulas (family Bythitidae), and others. [more]

Osmeriformes

Osmeriformes is an of ray-finned fish that includes various kinds of smelts, noodlefishes, and the odd-looking barreleyes. The order consists of fourteen families with about 240 species total. [more]

Osteoglossiformes

Osteoglossiformes (Gk. "bony tongues") is a relatively primitive of ray-finned fish that contains two sub-orders the Osteoglossoidei and the Notopteroidei. All of them live in freshwater. [more]

Palaeonisciformes

[more]

Perciformes

The Perciformes, also called the Percomorphi or Acanthopteri, include about 40% of all bony and are the largest order of vertebrates. The name Perciformes means perch-like. They belong to the ray-finned fish and comprise over 7000 different species, with varying shapes and sizes, found in almost all aquatic environments. They are also the most variably sized order of vertebrates, ranging from the 7mm (0.3 in) Schindleria brevipinguis to the 5m (16.5 ft) large Makaira species. They first appeared and diversified in the Late Cretaceous. Perciform fish typically have dorsal and anal fins divided into anterior spiny and posterior soft-rayed portions, which may be partially or completely separated. There are usually pelvic fins with one spine and up to five soft rays, either positioned by the throat or under the belly. Scales are usually ctenoid in form, though sometimes they are cycloid or otherwise modified. Various other, more technical characters define the group. [more]

Pleuronectiformes

The flatfish are an (Pleuronectiformes) of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. The name means "side-swimmers" in Greek. In many species both eyes lie on one side of the head, one or the other migrating through and around the head during development. Some species face their "left" side upward, some face their "right" side upward, and others face either side upward. [more]

Scorpaeniformes

Scorpaeniformes is an order of , but it has also been called the Scleroparei. Species in this order have recently been reclassified into the Perciformes. [more]

Siluriformes

Catfish ( Siluriformes) are a very diverse group of bony fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest, the Mekong giant catfish from Southeast Asia and the longest, the wels catfish of Eurasia, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. There are armour-plated types and also naked types, neither having scales. Despite their common name, not all catfish have prominent barbels; what defines a fish as being in the order Siluriformes are in fact certain features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby. [more]

Stomiiformes

Stomiiformes is an order of deep-sea of very diverse morphology, including dragonfishes, lightfishes, marine hatchetfishes, viperfishes, and loosejaws. The order comprises four families, more than fifty genera and a total of about 320 species. As usual for benthic fishes, there is no common name for all the species comprised in this order. [more]

Tetraodontiformes

The Tetraodontiformes are an of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the Perciformes. The Tetraodontiformes are represented by ten families and approximately 360 species overall; most are marine and dwell in and around tropical coral reefs, but a handful of species are found in freshwater streams and estuaries. They have no close relatives, and descend from a line of coral-dwelling species that emerged around 40 million years ago. [more]

Zeiformes

The Zeiformes are a small of marine ray-finned fishes most notable for the dories, a group of common food fish. The order consists of about 40 species in seven families, mostly deep-sea types. [more]

At least 65 species and subspecies belong to the Order Zeiformes.

More info about the Order Zeiformes may be found here.

Footnotes

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  1. ^ G. D. Johnson and E. O. Wiley (March 2007). "Tree of Life: Percomorpha".
  2. ^ R. Froese and D. Pauly (editors) (February 2006). "FishBase".
  3. ^ Nelson, Joseph, S. (2006). Fishes of the World. John Wiley & Sons, Inc.. ISBN 0471250317. 
  4. ^ Actinopterygii (TSN 161061). Integrated Taxonomic Information System. Retrieved on 3 April 2006.
  5. ^ In Nelson, Polypteriformes is placed in its own subclass Cladistia.
  6. ^ In ITIS, Gobiesociformes is placed as the suborder Gobiesocoidei of the order Perciformes.
  7. ^ In Nelson and ITIS, Syngnathiformes is placed as the suborder Syngnathoidei of the order Gasterosteiformes.

Sources

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Last Revised: November 18, 2008