Alyonushka hystricosa n. sp.

(Figs 2L, 24, 25)

Material examined. Holotype: ZIRAS 1/50711, colony attached to particle of nodule, YMG R.V. Gelendzhik cruise GLD4–09, Stn 199, 7 January 2011, 13.09042° N, 133.55185° W, 4758 m. One specimen only.

Etymology. Latin, hystricosus, prickly, thorny, alluding to the minutely prickled colony surface.

Description. Sole colony erect, pedunculate and subcalyciform, with outwardly flaring capitulum of relatively short autozooidal peristomes (Fig. 24), up to 10 in single irregular whorl. Column narrowest below middle, widening to slightly bulbous base thickened by development of layers of overlapping flattened alveoli/kenozooidlike chambers (Fig. 25D). Entire external skeletal surface of colony densely covered by minutely branched tiny prickles except for distal half of peristomes.

Surface of autozooidal peristomes irregularly granular-tubercular, tubercles tending to be slightly elongated and in partly linear series down sides of peristome (Fig. 25C). Aperture subcircular to suboval, rim thin, generally facing obliquely outwards. Interior of peristomes smooth or lightly textured, lacking spinulation (Fig. 25B, C, F).

Gonozooid occupying calyx center (Fig. 24A–C), large, slightly convex, its surface prickled, centrally imperforate, surrounded by irregular alveoli around periphery (Fig. 24A). Ooeciostome (Figs 24A–C, 25A, B, E), very short, subcircular, with thin prickled rim, inner surface with low irregularities (Fig. 25A). Ooeciopore smaller than autozooidal apertures.

Ancestrula and very early colony stages not seen.

Measurements (mm). Holotype, ZIRAS 1/50711 (Figs 24, 25): Colony height 2.08; capitulum 1.31 × 1.08; base diameter at substratum 0.69; minimum column diameter 0.43; ZL 0.403–0.618 (0.513 ± 0.068) (n = 9); PeL 0.213–0.303 (0.264 ± 0.026) (n = 9); PeD 0.128–0.153 (0.143 ± 0.010) (n = 9); ApL 0.154–0.175 (0.165 ± 0.008) (n = 9); ApW 0.106–0.128 (0.118 ± 0.007) (n = 9); OpD 0.087 (n = 1).

Remarks. Alyonushka hystricosa n. sp. is most readily distinguished from the type species and Alyonushka echinata n. sp. (below) by the smooth, non-spinulose inner surface of zooidal peristomes, as well as the surface appearance of the gonozooid.

Distribution. Recorded from a single station with coordinates 13.09042° N, 133.55185° W, at 4758 m depth.