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Octocorallia
	Dendronephtya klunzingeri
Scientific classification
Kingdom:	Animalia;
Phylum:	Cnidaria;
Class:	Anthozoa;
Subclass:	Octocorallia; Haeckel, 1866

Octocorallia (also known as Alcyonaria) is a subclass of Anthozoa comprising ~3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians (sea fans and sea whips) within three orders: Alcyonacea, Helioporacea, and Pennatulacea^[1]. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries. As with all Cnidarians these organisms have a complex life cycle including a motile phase when they are considered plankton and later characteristic sessile phase.

[edit] Phylogeny

Octocorallia is considered to be monophyletic, that is all contained species are descended from a common ancestor, but the relationships between subdivisions are not well known. The sea pens (Pennatulacea) and blue coral (Helioporacea) continue to be assigned separate orders, whereas the current order Alcyonacea was historically represented by four orders: Alcyonacea, Gorgonacea, Stolonifera, Telestacea.

The current phylogeny is shown below^[1], where Calcaxonia and Holaxonia are groups of gorgonians and the four remaining divisions of Alcyonacea are merely distinguished for convenience.