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Echinodermata

(Phylum)

Overview

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A phylum of marine coelomate animals that are bilaterally symmetrical as larvae but show pentamerous symmetry as adults and have a calcareous endoskeleton and a water vascular system. It includes the classes Crinoidea (sea lilies and feather stars), Asteroidea (starfish), Ophiuroidea (brittle stars), Echinoidea (sea urchins) and Holothuroidea (sea cucumbers).

Echinoderms are among the most distinctive of all animal phyla. They have a calcitic skeleton composed of many ossicles; a water vascular system; mutable collagenous tissue, and pentaradial body organization in adults.

The approximately 7,000 species of extant echinoderms fall into five well-defined clades: Crinoidea (sea lilies and feather stars), Ophiuroidea (basket stars and brittle stars), Asteroidea (starfishes), Echinoidea (sea urchins, sand dollars, and sea biscuits), and Holothuroidea (sea cucumbers).

Photos

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Taxonomy

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The Phylum Echinodermata is further organized into finer groupings including:

Classes

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Asteroidea

Starfish or sea stars are echinoderms belonging to the class Asteroidea. The names "starfish" and "sea star" essentially refer to members of the class Asteroidea. However, common usage frequently finds "starfish" and "sea star" also applied to ophiuroids which are correctly referred to as "brittle stars" or "basket stars". [more]

Blastoidea

Blastoids (Class Blastoidea) are an extinct type of stemmed echinoderm. Often called sea buds, blastoid fossils look like small hickory nuts. They originated, along with many other echinoderm classes, in the Ordovician period and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks. [more]

Crinoidea

Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters.[] Sea lilies refer to the crinoids which, in their adult form, are attached to the sea bottom by a stalk. Feather stars or comatulids refer to the unstalked forms. [more]

Cystoidea

The Cystoidea or cystoids, are extinct echinoderms that lived attached to the sea floor by stalks, and are distinguished from other echinoderms by triangular pore openings. [more]

Echinodermata

Echinoderms (Phylum Echinodermata) are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. Aside from the hard-to-classify Arkarua, the first definitive members of the phylum appeared near the start of the Cambrian period. [more]

Echinoidea

Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from 3 to 10 centimetres (1.2 to 3.9 in) across. Common colors include black and dull shades of green, olive, brown, purple, and red. They move slowly, feeding mostly on algae. Sea otters, wolf eels, triggerfish, and other predators feed on them. Their "roe" (actually the gonads) is a delicacy in many cuisines. [more]

Edrioasteroidea

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Holothuroidea

Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian species and genera, many of which are targeted for human consumption. The harvested product is variously referred to as trepang, b?che-de-mer or balate. [more]

Homoiostella

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Homostelea

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Ophiuroidea

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Somasteroidea

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Stelleroidea

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Stylophora

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At least 23 species and subspecies belong to the Class Stylophora.

More info about the Class Stylophora may be found here.

Sources

Last Revised: October 03, 2013
2013/10/03 15:44:45