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Elasmobranchii

(Subclass)

Overview

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Elasmobranchii is the of cartilaginous fish that includes skates, rays (batoidea), and sharks (selachii).

Summary

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Elasmobranchii is one of the two subclasses of cartilaginous fishes in the class Chondrichthyes, the other being Holocephali (chimaeras). For features that distinguish Elasmobranchii from Holocephali, see those articles. This classification includes great white sharks and the extinct megalodon.

Members of the elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placid scales. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The eyes have a tapetum lucidum. The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm. These fishes are widely distributed in tropical and temperate waters.[1]

Photos

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Taxonomy

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The Subclass Elasmobranchii is a member of the Class Chondrichthyes. Here is the complete "parentage" of Elasmobranchii:

The Subclass Elasmobranchii is further organized into finer groupings including:

Orders

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Carcharhiniformes

The ground sharks, order Carcharhiniformes, are the largest order of ; they are also called whaler sharks. With over 270 species, carcharhiniforms include a number of common types, such as the blue shark, catsharks, swellsharks, and sandbar shark. [more]

Cladoselachida

[more]

Echinorhiniformes

[more]

Heterodontiformes

The bullhead sharks are a small (Heterodontiformes) of very basal (primitive) modern sharks (Neoselachii). There are nine living species in a single genus, Heterodontus, in the family Heterodontidae. All are relatively small (50 to 150 cm)(20 to 59 inches) bottom feeders in tropical and subtropical waters. [more]

Hexanchiformes

Hexanchiformes is the consisting of the most primitive types of sharks, and numbering just five extant species. Fossil sharks that were apparently very similar to modern sevengill species are known from Jurassic specimens.(Allen, 45) [more]

Hybodontiformes

[more]

Lamniformes

Lamniformes is an of sharks, also known as mackerel sharks (which may also be used to refer to the sub-group of Lamniformes, Lamnidae). It includes some of the most familiar species of sharks, such as the great white shark, and some extremely rare types, such as the megamouth shark. [more]

Orectolobiformes

The order Orectolobiformes, also collectively known as the carpet sharks because many members have carpet-like patterned markings, includes a number of familiar types of , such as the nurse sharks and whale shark, as well as some unusual species, such as the blind shark. The order is small, with only 39 species in seven genera. [more]

Pristiformes

Sawfishes are a family of marine animals related to and rays. Their most striking appearance is a long, toothy snout. They are members of the sole family Pristidae within the order Pristiformes, from the Greek pristes meaning "a sawyer" or "a saw". [more]

Pristiophoriformes

The sawsharks or saw sharks are an order (Pristiophoriformes) of bearing long blade-like snouts edged with teeth, which they use to slash and disable their prey. There are five described (and four undescribed) species known, in a single family Pristiophoridae of two genera. Most occur in waters from South Africa to Australia and Japan, at depths of 40 m and below; in 1960 the Bahamas sawshark was discovered in the deeper waters (640 m to 915 m) of the northwestern Caribbean. [more]

Rajiformes

Rajiformes is the order of true rays and , flat-bodied cartilaginous fishes related to sharks. [more]

Squaliformes

Squaliformes is an of sharks that includes about 80 species in seven families. [more]

Squatinactida

[more]

Squatiniformes

The angel sharks are an unusual genus of with flattened bodies and broad pectoral fins that give them a strong resemblance to skates and rays. The 16-odd known species are in the genus Squatina, the only genus in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate and tropical seas. [more]

Symmoriida

[more]

Torpediniformes

The electric rays are a group of , flattened cartilaginous fish with enlarged pectoral fins, that comprise the order Torpediniformes. They are known for being capable of producing an electric discharge, ranging from as little as 8 volts up to 220 volts depending on species, used to stun prey and for defense. There are 69 species in four families. [more]

At least 83 species and subspecies belong to the Order Torpediniformes.

More info about the Order Torpediniformes may be found here.

References

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  1. ^ Bigelow, Henry B.; Schroeder, William C. (1948). Fishes of the Western North Atlantic. Sears Foundation for Marine Research, Yale University, pp. 64-65. ISBN B000J0D9X6. 

Sources

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Last Revised: November 18, 2008