Pennatulacea

Article By:

Williams, Gary C. Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, California.

Last reviewed:August 2019

DOI:https://doi.org/10.1036/1097-8542.496200

An order of the cnidarian subclass Octocorallia (class Anthozoa), which includes the sea pens, sea pansies, and veretillids, as well as a few species commonly called sea whips or sea feathers. The sea pens, sea pansies, and veretillids are illustrated in Fig. 1a, b, and c, respectively. The German equivalent for sea pens is die Seefedern. Some of the first-described pennatulaceans were called sea pens or sea feathers because of their resemblance to quill pens (pinnate or penniform in appearance); this was the derivation of the group name Pennatulacea (from the Latin penn or pinna for feather, pen, or wing). However, only a few taxa are feather-shaped; many others are sausage-shaped, flattened and foliate, narrow and whiplike, or even shaped like palm trees (Fig. 2). Pennatulaceans are benthic marine animals, as are all corals. However, they are unusual among corals in that the vast majority of species can anchor in soft sediments, such as mud, sand, fine rubble, or abyssal ooze, on the sea bottom, ranging from intertidal flats to the deep sea. A coral is defined here as an animal in the phylum Cnidaria (Coelenterata) that has some form of hard skeleton, which is composed of either calcium carbonate or a tough proteinaceous hornlike material (or a combination of both). Pennatulaceans are a highly specialized group of octocorals and differ markedly from soft corals and sea fans with regard to their colonial structure and habitat utilization. Morphologically, they are highly diverse (Figs. 1 and 2), with perhaps 300 or more valid species in 35 genera of 14 families. See also: Anthozoa; Cnidaria; Octocorallia (Alcyonaria)

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