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Class of cnidarians with 6-fold symmetry From Wikipedia, the free encyclopedia
Hexacorallia is a class of Anthozoa comprising approximately 4,300 species of aquatic organisms formed of polyps, generally with 6-fold symmetry. It includes all of the stony corals, most of which are colonial and reef-forming, as well as all sea anemones, and zoanthids, arranged within five extant orders.[2] The hexacorallia are distinguished from another class of Anthozoa, Octocorallia, in having six or fewer axes of symmetry in their body structure; the tentacles are simple and unbranched and normally number more than eight.[3] These organisms are formed of individual soft polyps which in some species live in colonies and can secrete a calcite skeleton. As with all Cnidarians, these organisms have a complex life cycle including a motile planktonic phase and a later characteristic sessile phase. Hexacorallia also include the significant extinct order of rugose corals.
Hexacorallia Temporal range: | |
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A stony coral, Acropora latistella | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Cnidaria |
Subphylum: | Anthozoa |
Class: | Hexacorallia Haeckel, 1896 |
Orders | |
Hexacorallia is considered to be monophyletic, that is all contained species are descended from a common ancestor, however it has been suggested that many of the current orders are not. Historically, Antipatharia was considered to be in a separate class called Ceriantipatharia, though more recent genetic studies place it in Hexacorallia.[2]
The class includes important coral reef builders such as the stony corals, sea anemones, and zoanthids. The recognized orders are shown below:[4]
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