Anthozoa

Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

Anthozoa is one of the three subphyla of Cnidaria, along with Medusozoa and Endocnidozoa. It includes sessile marine invertebrates and invertebrates of brackish water, such as sea anemones, stony corals, soft corals and sea pens. Almost all adult anthozoans are attached to the seabed, while their larvae exist as zooplankton. The basic unit of the adult is the polyp, an individual animal consisting of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new po

thumb|Aspidiscus cristatus from the Cenomanian (Upper [[Cretaceous) of southern Israel; oral view.]] thumb|Aspidiscus cristatus from the Cenomanian (Upper Cretaceous) of southern Israel; aboral view.

Octocorallia, along with Hexacorallia, is one of the two extant classes of Anthozoa. It comprises over 3,000 species of marine and brackish animals consisting of colonial polyps with eight-fold symmetry, commonly referred to informally as "soft corals". It was previously known by the now-unaccepted scientific names Alcyonacea and Gorgonacea, both deprecated , and by the also deprecated name of Alcyonaria, in earlier times.

order of cnidarians

Marine invertebrates

Reef building corals

Ceriantipatharia (rare synonym: Hexacorallia Goette, 1902 [non Haeckel, 1866]) is a taxon (usually a subclass) of Anthozoans used in some systems. It consists of the two taxa (usually orders) Ceriantharia (tube anemones) and Antipatharia (black corals).