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Containing group: Zoantharia

Characteristics

Anthozoa (Dodecacorallia), the proximal end of which is either rounded, physa-like or forms a more or less well-developed, flat pedal disc, without or with basilar muscles. Column smooth or provided with verrucae, tenaculi, vesicles, marginal spherules or pseudospherules or other specialisations [sic] of variable structure, often divisible into different regions, sometimes with spirocysts and with nematocyst batteries, rarely with ectodermal muscles. Margin indistinct or distinct, sometimes separated from the tentacles by a more or less developed fosse. Tentacles retractile or not, usually arranged hexamerously in alternating cycles but sometimes in radial series at least in the case of those communicating with the endocoels, usually simple, more rarely knobbed at the apex or branched or provided with papillae, exceptionally absent. Sphincter absent or present, endodermal to mesogloeal. Oral disc usually circular, but, sometimes drawn out into lobes of varying appearance. Actinopharynx shorter or longer usually with siphonoglyphs, typically two in number but varying from one to several. Siphonoglyphs usually connected with directive mesenteries, but very exceptionally the single siphonoglyph is more or less wholly separated from the actinopharynx. Pairs of mesenteries usually arranged in cycles, usually 6 + 6 + 12 etc. , a variable number of pairs perfect. From the stage with 6 pairs or later the subsequent mesenteries grow either (a) from the pedal disc upwards, or (b) from the oral disc downward, or (c) from the limbus and margin about simultaneously. Retractors of mesenteries of variable appearance from diffuse to circumscribed. Parietobasilar muscles more or less strong, in elongate individuals usually forming a well differentiated parietal muscle together with the parietal part of the longitudinal mesenterial muscles. Basilar muscles present or absent. Ciliated tracts of the filaments as a rule present. Acontia present or absent. Gonads situated at the same level as the filaments; their distribution variable, occasionally present only on the mesenteries of the last cycle, which sometimes lack filaments. Cnidom: spirocysts, atrichs, holotrichs, microbasic b- and p-mastigophors, microbasic and macrobasic amastigophors (these types never simultaneously present in any single individual).

Other Names for Actiniaria

• Sea Anemones

References

Carlgren, O. 1949. A Survey of the Ptychodactiaria, Corallimorpharia and Actiniaria. Kungl. Svenska Vetenskapsakadamiens Handlingar, series 4, volume 1, number 1.