Calyssopora clarionensis n. sp.

(Figs 33–35)

Material examined. Holotype: ZIRAS 1/50719, colony attached to nodule particle, YMG R.V. Gelendzhik cruise GLD4–11, Stn 220, 30 April 2012, 12.88593° N, 133.18168° W, 4916 m. Paratype 1: ZIRAS 2/50720, colony attached to nodule particle, YMG R.V. Yuzhmorgeologiya cruise YMG4–13, Stn 291, 27 July 2014, 13.00083° N, 132.49723° W, 4865 m. Paratype 2: ZIRAS 3/50721, colony attached to nodule particle, YMG R.V. Gelendzhik cruise GLD4–09, Stn 186, 1 January 2011, 13.45140° N, 133.53807° W, 4872 m. Paratype 3: ZIRAS 4/50722, detached colony, YMG R.V. Gelendzhik cruise GLD4–12, Stn 246, 3 April 2013, 13.00578° N, 132.95280° W, 4935 m. Additional material: YMG18–01, Stn 24; YMG4–07, Stn 134; GLD4–08, Stns 144, 150; GLD4–11, Stn 209; YMG4–13, Stns 287, 290; YMG4–14, Stns 327, 339. Total specimens examined 13.

Etymology. Pertaining to the Clarion Fracture, which defines the northern margin of the potential mining area.

Description. Colony erect, compact (Fig. 33) relative to other species, with apron-like base, vasiform; column topped by capitulum comprising peripheral autozooidal peristomes surrounding central concavity. Skeletal surface irregularly textured with minute dimples and granules except for base of column. Pores tiny, simple, sparse.

Autozooids in well-developed infertile colonies in single whorl of 6–7 (Fig. 35I –P), with incipient zooid bud developing frontally at lower level between each pair; apertures bilaterally symmetrical, with raised, granular, arcuate lateral rims and concave frontal and abfrontal rims (Figs 33A, 34A–F, M), hence somewhat mitriform in profile. Wall interiors densely covered by prickle-like granules (Fig. 34N, P). Alveoli rare between peristome bases abfrontally. Autozooids in mature brooding colonies with c. 8 peristomes in primary whorl and c. 7 slightly smaller peristomes at lower level (Fig. 34A).

Gonozooid single, developing from female zooid in central concavity of capitulum, ventricose in vicinity of ooeciostome only, occupying part or all of concavity, ooeciostome strongly curved and hood-like (Figs 33A, 34A, B, G, H, J), its surface granular-tubercular, ooeciopore concealed from frontal view. Sparse, relatively large alveoli adjacent to gonozooid within concavity (Fig. 34A, C).

Ancestrular zooid erect, not seen in isolation; earliest growth stage encountered comprising three very similar zooids (Fig. 35A–D) such that it is not clear which is ancestrular; protoecium not obvious. Elongation and outward curving of peristomes resulting in small vasiform colony (Fig. 35F–H) with budding of additional zooids lateroabfrontally between peristomes (Fig. 35M, N).

Measurements (mm). Holotype, ZIRAS 1/50719 (Fig. 33A): Colony height 1.94; capitulum 1.28 × 1.22; base at substratum 0.75 × 0.83; column diameter 0.47–0.76; ZL 0.653–0.882 (0.784 ± 0.088) (n = 8); PeL 0.221–0.303 (0.255 ± 0.026) (n = 8); PeD 0.203–0.233 (0.218 ± 0.011) (n = 8); ApL 0.196–0.228 (0.211 ± 0.011) (n = 8); ApW 0.155–0.192 (0.168 ± 0.013) (n = 8). Gonozooid (n = 1): GZL 0.483; GLW 0.491; OsL 0.348; OsW 0.226; OsH 0.207.

Paratype 2, ZIRAS 3/50721 (Fig. 33C): OpL 0.091 (n = 1); OpW 0.108 (n = 1).

Paratype 3, ZIRAS 4/50722 (Fig. 33D): OpL 0.098 (n = 1); OpW 0.124 (n = 1).

Remarks. Calyssopora clarionensis n. sp. differs most obviously from the type species in having a gonozooid with a curved ooeciostome and prickled zooidal interiors.

Distribution. Recorded from 13 stations within coordinates 12.84500– 14.33668° N, 129.07338– 134.46597° W, at depth range 4690–5222 m.