Scleractinia

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Scleractinia (Madreporaria; stony corals; subclass Zoantharia) Order of solitary or, more commonly, colonial corals, which always possess an external calcareous skeleton consisting essentially of radial partitions (septa, see SEPTUM). Septa develop following the pattern of the radial infoldings in the body wall (mesenteries) in cycles of 6, 12, 24, 48, etc. The order first appeared in the Middle Triassic.

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