Alyonushka filia Grischenko & Gordon & Melnik 2018, n. sp.

Alyonushka filia n. sp.

(Figs 21–23, 52)

Material examined. Holotype: ZIRAS 1/50710, colony attached to particle of nodule, YMG R.V. Gelendzhik cruise GLD4–08, Stn 164, 4 August 2009, 13.26703° N, 133.84563° W, 4922 m. Paratype: NIWA 127724, colony attached to particle of nodule, YMG R.V. Yuzhmorgeologiya cruise YMG4–07, Stn 123, 31 July 2007, 13.29668° N, 134.17724° W, 4774 m. Additional material: YMG4–04, Stn 48; GLD4–08, Stn 156; GLD4–09, Stns 173, 180, 195; GLD4–11, Stns 222, 224, 227; GLD4–12, Stns 235, 236; YMG4–13, Stns 294, 299, 319; YMG4–14, Stns 351, 357, 363, 365. Total specimens examined 19.

Etymology. Latin, filia, daughter, linking with the genus name; used as a noun in apposition.

Description. Colony erect, pedunculate and subcalyciform, with outwardly flaring capitulum of relatively long autozooidal peristomes in mature colonies (Fig. 21A, B), up to maximum of c. 27 long and short peristomes in single irregular whorl; lower parts of some peristomes fused with shorter neighbors in slightly more abfrontal position. Calyx center in immature colonies bowl-like with a few relatively large peripheral alveoli. Column narrowest in middle, widening evenly to moderately broad base. Entire external skeletal surface of colony minutely and excessively prickled (Fig. 22F–J, L). Skeletal microstructure of generally irregular angular imbricated crystallites (Fig. 22E). Proximal half of column may become thickened by development of layers of overlapping flattened, cushion-like alveoli/kenozooid-like chambers.

Autozooidal peristomes with staggered barbed ridges (Figs 21, 22A–D). Pores simple, small, sparse (Fig. 22D). Apertures rounded, the rims bearing up to 10 evenly spaced projections of peristomial ridges (Fig. 22A, C–E, I, K). Interior of peristomes with simple scattered spinules (Fig. 22K); these longer and more acicular in openings of developing zooids (Fig. 22F).

Gonozooids 1–2 per mature colony (Figs 21A–C, 22A), occupying calyx center, large, convex; surface highly irregular owing to rims of adjacent alveoli bearing irregularly oriented thorn-like processes (Figs 21C, 22B), all minutely prickled (Fig. 22G). Incubation-chamber floor continuous (Figs 21E, 52C). Ooeciostome(s) relatively broad and low, ooeciopore subrounded, very little elevated, thin-walled; inner face with sparse granulation (Fig. 22J, L). CT scans show narrow shelf within ooeciostome at inner entrance to gonozooid (Fig. 52C).

Ancestrula not seen in isolation, but erect judging from smallest (four-zooid) colony stages seen (Fig. 23A–J); CT scans confirm protoecial dome with erect peristome arising from its center, with first daughter zooid also produced from dome adjacent to it (Fig. 52D, E). Low trabeculae form in center of developing colony to support continuing elevation and expansion, with extrazooidal alveolar spaces between trabeculae and kenozooid-like chambers supporting stem.

Measurements (mm). Holotype, ZIRAS 1/50710 (Fig. 21A, B): Colony height 3.20; capitulum 2.44 × 1.86; attachment base 1.15 × 1.03; stalk height 1.71, thickness 0.45 × 0.41 to 0.80 × 0.77; ZL 0.932–1.238 (1.062 ± 0.102); PeL 0.593–1.055 (0.812 ± 0.138); PeD 0.151–0.173 (0.160 ± 0.007); ApL 0.130–0.154 (0.143 ± 0.009); ApW 0.103–0.125 (0.116 ± 0.007). Gonozooid 1 (n = 1): GZL 0.695; GZW 0.410; OsL 0.123; OsW 0.101. Gonozooid 2 (n = 1): GZL 0.780; GZW 0.558; OsL 0.130; OsW 0.116.

Non-type specimen GLD4–09, Stn 173 (Fig. 23A, B): AnPeD 0.123 (n = 1).

Remarks. Alyonushka filia n. gen., n. sp. is distinguished from the following two new species by its much longer, barbed, peristomes and spinose apertures, as well as the chaotic thorny surface of its gonozooid(s).

Distribution. Recorded from 19 stations within coordinates 12.55585– 14.57215° N, 130.83310– 134.17724° W, at depth range 4774–5275 m.