Stylantheca Fisher, 1931

Cairns, Stephen D. & Lindner, Alberto, 2011, A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters, ZooKeys 158, pp. 1-88 : 54

Genus Stylantheca Fisher, 1931

Diagnosis.

Colonies encrusting, forming thin laminae on rocks and shells, rarely forming short stubby branches. Coenosteum reticulate-granular and of many colors; coenosteal papillae quite common. Gastro- and dactylopores arranged in cyclosystems, often with more than one gastrostyle per cyclosystem; pores of the peripheral type; supernumerary dactylopores rare. Gastropore tube single-chambered, but may be constricted by a ring palisade. Dactylostyles usually robust. Ampullae usually internal.

Discussion.

As summarized by Cairns (1983b), species attributed to this genus have been placed in the genera Allopora , Stylaster , and as a subgenus of Stylaster . Stylantheca papillosa (Dall, 1884) is indeed very similar to Stylaster (Group A, i.e., Allopora ). At present the only characters differentiating Stylantheca from Stylaster (Group A) is its tendency to form encrusting colonies, and its tendency to have more than one gastrostyle per cyclosystem, although there are exceptions to both of those criteria. Deeper water colonies of Stylantheca papillosa often have short stubby branches, and the northern range of Stylantheca papillosa sometimes has only one gastrostyle per cyclosystem (see Remarks of Stylantheca papillosa ). It is likely that Stylantheca belongs to the Stylaster genus, perhaps as a fifth group, i.e., "Group E", of species sensu Cairns (1983b) that would include encrusting species with a tendency to have multiple gastrostyles per cyclosystems. But until more specimens have been collected to study morphological variation, we choose to retain the genus Stylantheca .

Type species.

Stylantheca porphyra Fisher, 1931, by monotypy.

Distribution.

From the Alaska Peninsula to Lower California, 0-27 m.