Stylaster repandus Cairns & Lindner 2011

375-475 m

Colonies firmly attached to a hard substrate by a robust basal stem and encrusting base, the base being 9 cm in diameter and the basal stem 5 cm in diameter in the case of the holotype. Immediately above basal stem the colony divides into two or three lamellae (Fig. 27C), each lamella (or sheet) of coenosteum increasing its surface area by folding its surfaces into a complex three-dimensional structure similar to that of Cyclohelia. Short (up to 15 mm) cylindrical branches project from plane of colony, but always in response to housing a parasitic spionid worm tube. Holotype (Fig. 27A–B) 23 cm tall and 19 cm in width. Coenosteal lamellae thin at edge, only 2.0–2.5 mm thick, and thus easily damaged during collection; basal lamellae up to 10 mm in thickness. All colonies examined heavily infested with spionid worm tubes. Coenosteum reticulate-granular in texture, the strips being about 30 µm wide, bordered by slits about 9–19 µm thick; granules spinose. Coenosteum covered uniformly with small papillae (Fig. 28B). Coenosteum light orange, but central core a light shade of pink. Cyclosystems equally common on both faces of lamellae, and even occur on lamellar edges, often arranged in transverse rows of up to 15 cyclosystems that parallel lamellar edge; diameter of cyclosystems 1.0–1.15 mm. Gastropore tube funnel-shaped near branch surface, and straight but constricted, the upper diameter being about 0.34 mm in diameter, the constriction corresponding to a diffuse ring palisade, the blunt elements being up to 60 µm tall and 40 µm in diameter. Gastrostyles lanceolate, pointed, and bear longitudinal, spinose ridges. Illustrated style (Fig. 28D) 0.53 mm in height and 0.26 mm in basal diameter. Cyclosystems almost flush with coenosteum, the dactylopore slits raised only slightly above coenosteum; dactylotomes 0.15-0.17 mm in width. Based on 74 cyclosystems the range of dactylopores per cyclosystem is 1-11 (average = 3.94 (σ = 2.05), and mode = 4). In many cyclosystems there is an adcauline diastema (Fig. 28E), often produced by the infilling of 1–3 adcauline dactylopores, these dactylopores becoming obsolete. Dactylostyles robust, composed of an almost unilinear arrangement of cylindrical, blunt to clavate elements up to 60 µm tall and 13–15 µm in diameter (Fig. 28D, H, J–K). Female ampullae (Fig. 28L–M) low swellings on coenosteum 0.9–1.1 mm in diameter (internal diameter 0.7–0.8 mm), each with a peripheral efferent pore 0.3–0.4 mm in diameter that faces upward. Male ampullae (Fig. 28I) densely arranged, superficially visible only as inconspicuous mounds 0.5–0.6 mm in diameter (internal diameter 0.4–0.5 mm), often with an irregularly shaped apical efferent pore about 60 µm in diameter.

Known only from three localities in the vicinity of Amukta Island, Aleutian Islands; 375–475 m.