A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters Author Cairns, Stephen D. Author Lindner, Alberto text ZooKeys 2011 158 1 88 http://dx.doi.org/10.3897/zookeys.158.1910 journal article http://dx.doi.org/10.3897/zookeys.158.1910 1313-2970-158-1 Stylaster elassotomus Fisher, 1938 Figs 21C25 A-G Stylaster elassotomus Fisher, 1938: 499-500, pl. 41, fig. 3, pl. 42, figs 1-1c, pl. 49, fig. 1.- Boschma 1957 : 7.- Wing and Barnard 2004 : 11 (key), 28.- Heifetz et al. 2005 : 134, 137 (listed).- Stone and Shotwell 2007 : 108 (listed).-Jameison et al. 2007: 224 (listed). Type material. Holotype: 1 dry male colony, and SEM stub 1507, USNM 43268 (Fig. 21C). The pale pink paratype 5 cm in length (USNM 86007) mentioned by Fisher is an unidentified Stylaster having little in common with the holotype. Type locality.Albatross 4781, 52°14'30"N , 174°13'E (off Agattu Island), 882 m. Material examined. Types. Description. Holotype (Fig. 21C) colony bushy, 5.5 cm tall and 4.5 cm wide, attached by a basal branch 6 mm in diameter. Branches do not anastomose and are circular in cross section. Coenosteum reticular-granular in texture, the strips 55-60 µm in width, separated by slits 10-14 µm wide; strips covered with small angular granules. Spionid worm tubes absent. Coenosteum white. Cyclosystems circular to slightly elliptical, 1.0-1.2 mm in diameter, arranged exclusively on branch edges in an alternating fashion, most projecting perpendicular to branch. Gastropores circular and quite large (0.5-0.6 mm in diameter), occupying up to 55% of cyclosystem diameter (Fig. 25F). Gastropore tube cylindrical, curved, and long, such that gastrostyle tip is rarely seen when viewed from above (Fig. 25A). A delicate ring palisade (Fig. 25 C-D ) occurs near gastrostyle tip, composed of slender cylindrical elements up to 60 µm long and 25 µm in diameter. Gastrostyle slender (H:D = 4.4), the illustrated style 0.53 mm in height, occupying lower quarter of gastropore tube (Fig. 25A). Dactylotomes 60-80 µm wide but very short as well as having short internal slits, thus contributing to the large size of the gastropore tube (Fig. 25F); dactylostyles inconspicuous. Range of dactylopores per cyclosystem 11-17 (n = 21, average = 14.40 (σ = 1.36), and mode = 15). Supernumerary dactylopores common (Fig. 25B), 70-100 µm in diameter. Pseudosepta same width as dactylotomes; diastemas rare. Female ampullae unknown. Male ampullae (Fig. 25G) hemispherical, 0.5-0.6 mm in diameter. Remarks . Despite access to a diverse stylasterid collection from the Aleutian Islands, no unequivocal additional specimens could be identified as Stylaster elassotomus , even the paratype of the species not considered to be conspecific. Its distinctive characteristics of having a highly curved gastropore tube, slender ring palisade elements, and a very large gastropore surrounded by very short dactylotomes and pseudosepta distinguish it from all other Alaskan species (see Table 2). Distribution. Known only from type locality. Figure 25. Holotype (male) of Stylaster elassotomus , USNM 43268: A stereo view of curved gastropore tube B cyclosystems and supernumerary dactylopores C poorly preserved gastrostyle and ring palisade D truncated gastrostyle showing ring palisade E coenosteal texture F stereo view of cyclosystem showing shallow dactylotomes G male ampulla.