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Scyphozoa
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Scyphozoa

Scyphozoa is a class of jellyfish.^[1]

Scyphozoans are members of the phylum Cnidaria and are referred to as the "true jellyfish." Scyphozoans range from the Ediacarian time period through the Recent. In Scyphozoans, the medusa form is dominant life stage, while the polyp form may be a juvenile stage. As medusae, they eat a variety of crustaceans and fish, which they capture using stinging cells called nematocysts. The nematocysts are attached to the tentacles that radiate downward from the edge of the umbrella dome. Scyphozoans display a four-part symmetry and have an internal gelatinous material called mesoglea. Scyphozoans have no durable hard parts, including no head, no skeleton and no specialized organs for respiration or excretion.^[2][3] Marine jellyfish can consist of as much as 99% water and therefore are rarely found in fossil form.

Unlike other Cnidarians, scyphozoans lack a velum, which is a circular membrane umbrella that propels the jellyfish through the water. While scyphozoans lack this specialized locomotive device, they are able to move through the water by contracting and relaxing the muscles of their umbrella.^[4] The periodic contracting and relaxing propels the jellyfish through the water, allowing it to escape predation or catch its prey.

It includes the genus Aurelia.^[5]

[edit] Orders

• Order Coronatae
• Order Semaeostomeae
• Order Rhizostomeae

[edit] References

[edit] External links

• The Classification and Distribution of the Class Scyphozoa

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