Alcyonacea

Alcyonacea (synonyms: Alcyonaria, Alcyonarida), in English soft corals or alcyonacians, is a former order (or suborder) of Octocorallia. Since a 2022 revision of Octocorallia, the content of Alcyonacea has been included in the order Malacalcyonacea and, to a lesser extent, in the order Scleralcyonacea, these two new orders now making up the order Octocorallia.

Definition of the order

There are three basic ways of delimiting the order Alcyonacea:

It some systems it corresponds to what is called suborder Alcyoniina in other systems (see the system stated below in this article for Alcyoniina).

In other systems, it includes not only the Alcyoniina, but also the taxa Stolonifera, Telestacea (included in Stolonifera by some authors) and Protoalcyonaria, which are classified as separate orders by other authors.

In the broadest sense, it includes not only the Alcyoniina, Stolonifera, Telestacea and Protoalcyonaria, but also the taxa (suborders) Scleraxonia, Holaxonia and Calcaxonia (former name: "restricted Holaxonia"), which, in other systems (and in all systems before 1981), were together classified as the separate order Gorgonacea (synonyms: Gorgonarida, Gorgonaria), in English called gorgonians or sea fans (and sea whips). This definition of Alcyonacea is also used in the following text of this article.

The following text should be considered a historical, outdated way of treating the taxonomy of Anthozoa and Octocorallia.

Introduction

Alcyonacea are sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Whilst not in a strict taxonomic sense, Alcyonacea are commonly known as soft corals. The term "soft coral" generally applies to organisms in the two orders Pennatulacea and Alcyonacea with their polyps embedded within a fleshy mass of coenenchymal tissue.