A class of teleostom fishes commonly known as the ray-finned fishes, which are distinguished by the structure of the paired fins that are supported by dermal rays. The class Actinopterygii comprises the subclasses Cladistia [Polypteriformes (bichirs and reedfishes) and fossil orders], Chondrostei [Acipenseriformes (sturgeons and paddlefishes) and fossil orders], and Neopterygii (the remaining actinopterygian orders) [Fig. 1]; however, it should be noted that some recent taxonomies now place the cladistians within the chondrosteans. The members of the Neopterygii, minus the Holostei [consisting of members of the Lepisosteiformes (gars), Amiiformes (bowfins), and several fossil taxa], comprise the Teleostei. Overall, the members of the Actinopterygii make up about half of all vertebrate species and approximately 96% of all currently existing fishes. Collectively, the class Actinopterygii is considered to be a nonmonophyletic group that is derived from more than one lineage when tetrapods are excluded. The Actinopterygii and the Sarcopterygii, minus the Tetrapoda, comprise the Osteichthyes (the bony fishes). The Actinopterygii includes more than 40 orders, about 430–480 families, more than 4000 genera, and about 27,000 described extant species. Many species are known to science, but are not yet described; furthermore, in regions such as the Amazon and Congo basins, species are probably becoming extinct before they are discovered and described in the scientific literature. See also: Acipenseriformes; Amiiformes; Holostei; Lepisosteiformes; Ostariophysi; Osteichthyes; Polypteriformes; Sarcopterygii; Teleostei; Teleostomi; Tetrapoda

The true eels, a large order of actinopterygian fishes, also known as the Apodes. The order Anguilliformes is related to Saccopharyngiformes (sackpharynx fishes), Elopiformes (tarpons), and Notacanthiformes (spiny eels and halosaurs); all members have a leptocephalous (slender and transparent) larval stage in development. The chief characteristics of the Anguilliformes include the following: an elongate body with numerous vertebrae; a pectoral girdle that, when present, is free from the head; absence of a pelvic girdle and pelvic fins in extant adults; dorsal and anal fins that are confluent with the caudal fin (the caudal fin is absent in some ophichthids); loss of skeletal parts, especially those about the head (for example, the orbitosphenoid, posttemporal, and symplectic bones, as well as the gular plate, are absent); mesocoracoid and postcleithra are absent; swim bladder is present, usually physostomous (that is, having a connection to the esophagus); restricted gill openings; no fin spines; scales are usually absent or, if present, cycloid and embedded in the skin; and 6–49 branchiostegal rays. See also: Actinopterygii; Eel; Elopiformes; Notacanthoidei; Saccopharyngiformes; Swim bladder

An order of teleost fishes, comprising the argentines or herring smelts, in the superorder Protacanthopterygii. Members of the order Argentiniformes are marine, deep-water fishes. They are identifiable by the following combination of characters: a variable body, being elongate and cylindrical in some to short and compressed in others; a greatly reduced jaw mechanism; a greatly reduced dentition; a premaxillary bone that is absent in some species, but lacking teeth if present; a usually toothless maxillary bone; eyes variously directed, with some species having tubular eyes; some species with specialized light organs, which may be associated with tubular eyes; no serial photophores; an adipose fin that can be present or absent; a forked caudal fin; and a physoclistous (not attached to the gut) swim bladder that can be present or absent. In addition, the argentines have a crumenal organ (paired branchial pouches in which food particles are trapped by large interlocking toothed gill rakers). See also: Actinopterygii; Osteichthyes; Photophore gland; Swim bladder; Teleostei

The common name for any of the perciform fishes belonging to a single genus, Sphyraena, in the family Sphyraenidae. Barracudas are characterized by an elongate, slightly compressed body; a long, pointed head; a large horizontal mouth with nonprotractile premaxillae and with the lower jaw projecting beyond the upper jaw; strong, sharp, uneven conical teeth in the jaws as well as in the roof of the mouth (palatine teeth) and usually a large canine tooth near the tip of the lower jaw; two short dorsal fins, with the first located above the pelvic fins and having five strong spines, and the second usually with one spine and nine soft rays, as well as being well removed from the first and a mirror image of the anal fin; short pectoral and pelvic fins; a forked caudal fin; cycloid scales that are smooth to the touch; and coloration that is usually gray to green or bluish above, with silvery reflections, and lighter below, and sometimes with dark vertical bars or chevrons (see illustration).

A common name applying to a large group of fishes, mostly in the order Perciformes, generally having the following characteristics: body about 2.5–3 times longer than its depth; two dorsal fins, with the first composed of stiff spines; pectoral fins on the sides of the body just behind the head; pelvic fins that are thoracic in position, with one spine and five rays; ctenoid scales; a relatively large mouth; and a predatory lifestyle. However, because bass is not a taxonomic unit, the term cannot be precisely described or defined. In the western North Atlantic, eastern North Pacific, and freshwaters of Central and North America alone, the word bass appears in the vernacular of 53 species and six hybrids in 17 genera and six families. A generally accepted limited taxonomy of the basses is listed below. (The initial A indicates a North Atlantic range; P indicates a North Pacific range; and F indicates freshwaters of Central America and North America.) Fishes called basslets (primarily of the family Grammatidae) are not included. See also: Perciformes

An elasmobranch subdivision of cartilaginous fishes known collectively as the rays, skates, or batoids. Batoidea is one of the two subdivisions of the subclass Elasmobranchii (class Chondrichthyes) and consists of 4 extant orders, 17–20 families, and more than 600 species. The other subdivision, Selachii, includes the sharks. Some investigators group the modern sharks and several families of fossil sharks plus the modern rays in a superorder, Euselachii, supposedly a monophyletic unit. Others group all recent sharks and rays in two separate subdivisions, Selachii and Batoidea, respectively, as presented herein.

An order of somewhat intermediate position among actinopterygian (ray-finned) fishes. Members of the order Beryciformes share the following features with the perciform fishes: fin spines, ctenoid scales, an upper jaw bordered by the premaxillae, a ductless swim bladder, and the absence of a mesocoracoid. An orbitosphenoid bone is present, as is typical of many lower teleosts. The pelvic fins are thoracic or subabdominal in position, and each has a spine and 3 to 13 rays (usually there are more than 5); the pelvic girdle is most often attached to the cleithra; and there are 18 or 19 principal caudal rays. See also: Actinopterygii; Osteichthyes; Perciformes; Scale (zoology); Swim bladder; Teleostei

The common name for a number of freshwater cypriniform fishes of the family Cyprinidae. The carp originated in China, where for centuries it was raised for food. It was imported into the United States from Europe, where it also has been raised for years as a source of food. See also: Aquaculture; Cypriniformes; Fisheries ecology; Teleostei

The only extant order of the chondrichthyan subclass Holocephali, comprising the ratfishes. Members of the order Chimaeriformes (chimaeriforms or ratfishes; Fig. 1) are the closest living relatives of members of the subclass Elasmobranchii (sharks and rays). They are a distinctive group of marine fishes that mostly inhabit the deeper parts of the world's oceans, especially in the Atlantic and Pacific. Some species move to coastal waters during the winter months, and a few species may be restricted to these environments. Modern ratfishes are divided into three families (Callorhinchidae, Chimaeridae, and Rhinochimaeridae), which are distinguished by the shape of the snout. See also: Chondrichthyes; Elasmobranchii

A class of vertebrates comprising the cartilaginous, jawed fishes. Members of the Chondrichthyes (chondrichthyans, or the cartilaginous fishes) are characterized by well-developed jaws and bony teeth; pectoral and pelvic girdles, with each supporting paired fins; a cartilaginous skeleton that lacks true bone; toothlike scales of ectodermal and mesodermal origin; paired nostrils with blind olfactory sacs (not opening into the mouth); a vertebral column having either a straight or heterocercal posterior end; the absence of a swim bladder; a cranium without sutures; and internal fertilization. Traditionally, the class Chondrichthyes includes the subclasses Holocephali (chimaeras) and Elasmobranchii [sharks (see illustration), rays, and skates]. A group of Devonian armored fishes, the Placodermi, has been regarded as ancestral to the Chondrichthyes, but this derivation is not certain. Another group of primitive jawed fishes called acanthodians, considered by many as ancestral to the higher bony fishes, exhibit certain primitive elasmobranch-like features. In any case, it is probable that the elasmobranchs and chimaeras arose independently of each other during the Silurian or Early Devonian. Because even calcified cartilage is rarely preserved, the fossil record of the Chondrichthyes is represented mainly by teeth and spines, with only occasional associated skeletons. See also: Acanthodii; Cartilage; Gnathostomata; Placodermi; Vertebrata