A stony coral, Acropora latistella

Hexacorallia is a subclass of Anthozoa comprising approximately 4,300 species of water-based organisms formed of colonial polyps generally with 6-fold symmetry. This includes all of the stony corals, which are vital for coral reef formation, as well as all sea anemones, tube anemones, and zoanthids within six extant orders.[1] They are distinguished from the other subclass of Anthozoa, Octocorallia, in having six or fewer lines of symmetry in their body structure and only single rows of tentacles. These organisms are formed of individual soft polyps which in some live in colonies and can secrete a calcite skeleton. 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. It also includes the significant extinct orders of the rugose corals and tabulate corals


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 Ceriantharia and Antipatharia were considered to be a separate subclass called Ceriantipatharia, though more recent genetic studies place them in Hexacorallia with Ceriantharia as the oldest, or basal, group.[1]

The subclass includes important coral reef builders the stony corals (Scleractinia), sea anemones (Actiniaria) and related tube-dwelling anemones (Ceriantharia), and zoanthids (Zoantharia). Antipatharia contains the black corals and Corallimorpharia are similar to anemones. The extant orders are shown below:[1]








A number of extinct orders of corals have been classified as their calcium skeleton forms a prolific fossil record. These are generally thought to be close to the ancestors of modern Scleractinians and existed during the Paleozoic Era 541-242 million years ago:[2][3]

  • Numidiaphyllida †
  • Kilbuchophyllida †
  • Heterocorallia †
  • Rugosa
  • Heliolitida †
  • Tabulata
  • Cothoniida †
  • Tabuloconida †

Hexacorallia or Zoantharia

The terms Hexacorallia and Zoantharia have been used synonymously to avoid confusion with some of the extinct species not showing sixfold symmetry. For example, Rugosa † is also called Tetracorallia, for its fourfold symmetry. Therefore, Hexacorallia might appear misleading, and Zoantharia is sometime preferred in paleontological contexts. However, with Zoantharia being the name used since 1899[4] until recent days [5][6] for the hexacorallian order Zoantharia, the use of the term Hexacorallia is strongly recommended[by whom?] in order to avoid confusions.


External links

  • Tree of Life Zoantharia
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.