Psolidium poriferum , syn. nov.

Psolidium poriferum (Studer) syn. nov.

Figures 2d; 7 c-f

Cuvieria porifera Studer, 1876: 452–53.— Studer, 1879: 123.

Psolusporiferus.— Bell,1882:644.— Lampert,1889:854.— Studer, 1889: 163.

Psolus poriferus (Cuvieria).— Théel, 1886: 130.— Lampert, 1885: 122.

Psolus incertus Théel, 1886: 86–87, pl. 8 fig. 4, pl. 6 fig. 5.— Studer, 1889: 163. (new synonymy).

Theelia incerta.— Ludwig, 1892: 350.

Theelia (? Psolidium) incerta.— Ludwig, 1894: 136.— Ludwig, 1898: 52.

Theelia porifera (part).— Ludwig, 1898: 52.— Pawson, 1969: 38.

Psolidium incertum.— Pawson, 1969: 38, map 3.— Pawson, 1971: 34, 37.— Guille, 1982: 70.— Massin, 1992: 317, 320–21, figs 8–9.— Branch, Jangoux, Alvá, Massin and Stampanato, 1993: 56, 61–65.— Thandar, 1999: 368.— Thandar, 2006: 38.

Psolidium poriferum.— Pawson, 1971: 34, 37.— O’Loughlin and Maric, 2008: 3

Material examined. Psolidium poriferum (Studer, 1876) holotype: Kerguelen, Royal Sound, Gazelle, 119 m, ZMB 2259.

Psolidium incertum (Théel, 1886) syntypes (3; very poor condition): Kerguelen, Royal Sound, Challenger stn 149c, BM(NH) [18]86.10.2.89 (1); Heard I., stn 150, BM(NH) [18]86.2.88 (1); stn 151, BM(NH) [18]86.10.2.90 (1).

Other material: Indian Ocean, McDonald Is, 210–234 m, USNM 1081576 (2 specimens); S of Kerguelen I., BANZARE stn 47, 150 m, SAM K2344 (23); Heard I., ANARE Aurora Australis AA 90, 200 m, SAM K2189 (1); 260–380 m, K2190 (1); 260 m, K2191 (1); 266–380 m, K2205 (1); ANARE Aurora Australis AA 92, 185–204 m, NMV F66849 (1); 229 m, F66850 (1); Heard I., F/ V Southern Champion, cr SC26, Apr / May 2003, Western Plateau, 264–406 m, TMAG H3303 (1), H3306 (2), H3308 (2), H3317 (1), H3320 (4); Aurora Bank, 222–292 m, H3304 (4), H3305 (3), H3307 (4), H3309 (2), H3313 (2), H3314 (2), H3315 (1), H3318 (3), H3321 (6), H3322 (1); Coral Bank, 293–297 m, H3310 (3), H3311 (4); Shell Bank, 259–329 m, H3312 (1), H3316 (3), H3319 (2).

Eastern Antarctica, MacRobertson Land, BANZARE stn 107, 66°45’S 62°03’E, 177 m, SAM K2343 (1).

Diagnosis. Psolidium species up to 33 mm long; body form elongate, narrow, high; dorsal and lateral scales conspicuous, thin, smooth, up to 1.8 mm wide; dorsal and lateral tube feet inconspicuous.

Sole: outer peripheral single series of smaller tube feet; inner peripheral single series of larger tube feet; lacking mid-ventral (sole) radial series of tube feet.

Dorsal ossicles: multi-layered perforated plates (scales), single-layered marginally, frequently with well developed radiating-to-margin linear rounded thickenings between series of perforations, reticulate thickenings towards centre of plates, multi-layered centrally; up to 3 tube foot canals per plate.

Sole ossicles: throughout most of sole rare, small, smooth, thin, irregularly shaped rods and perforated plates, 0–10 perforations, bluntly spinous around margin, sometimes surface knobs, up to 220 μ m long; sometimes as regular 4-holed plates with marginal knobs, sometimes surface knobs, up to 160 μ m long; near margin of sole and peripheral tube feet some thicker, irregular perforated rod-plates, surface with linear thickenings and large knobs, rod-plates up to 370 μ m long, intergrading with oval to elongate perforated plates with secondary layering, up to 400 μ m long.

Tentacles: largest tentacle trunk ossicles irregular round to triangular to oval, thick perforated plates, irregular large perforations, some small plates with secondary layering, plates up to 650 μ m long; some plates with irregular linear thickenings between perforations (suggesting rod origin), some rod-plates up to 800 μ m long.

Colour (preserved). Body off-white; scales not haloed.

Distribution. Marion, Prince Edward, Kerguelen, Heard and McDonald Is, 100–600 m (Massin, 1992), 150–406 m (this work); Eastern Antarctica, MacRobertson Land, 177 m.

Remarks. Pawson (1971) indicated that the evidence was “quite strong” for a synonymy of P. incertum with P. poriferum, and O’Loughlin and Maric (2008, this volume) inferred this synonymy. Both species were described from the same type locality. Based on an examination of the type materials and the literature, Psolidium incertum (Théel, 1886) is synonymised here with Psolidium poriferum (Studer, 1876). Psolidium poriferum occurs abundantly on the Sub-Antarctic Islands of the Indian Ocean, with the exception of a single BANZARE specimen found on the MacRobertson Shelf on the Antarctic coast. Psolidium poriferum (Studer) is distinguished diagnostically by the frequent occurrence on the scales of well developed radiating-to-margin linear rounded thickenings between series of perforations.