Polyps of some anthozoan species are gonochoric, those of some species are hermaphroditic, and those of still others change sex during their lifetime. The actinopharynx of each polyp has a single siphonoglyph. Alcyonarians of most species form colonies and skeletons. Despite the name of the subclass, almost no members have six tentacles. Depending on the taxon, one or more than one tentacle may arise from each intermesenterial space.
Black corals are the only exclusively colonial zoantharians.
Discussion of Phylogenetic Relationships Class Anthozoa is traditionally considered to have two or three subclasses. 1994, Bridge et al. 1995, Chen et al. The phylogenetic relationships of anthozoan subgroups are currently the subject of much debate. In the above Discussion of Phylogenetic Relationships, Daphne Fautin and Sandra Romano have given a summary of the most important issues. Many open questions remain, and there is some controversy about the conclusions that can be drawn from the data collected to date.