Psolus parantarcticus Mackenzie & Whitfield, 2011, sp. nov.

Psolus parantarcticus sp. nov.

Table 1, Figures 4 a–f.

Material examined. Holotype. Australia, Macquarie I., off Nuggets Point, 54°33.4'S 158°56.9'E, 108–135 m, ANARE, MV Nella Dan, Cochrane, T., 8 Dec 1986, NMV F60306.

Paratypes. Type locality and date, NMV F176181 (1), NMV F160012 (4).

Other material. Australia, Macquarie I., 54°S 159°E, USNS Eltanin, 1968, USNM E33625 (1); Australia, Macquarie I., 112–124 m, USNS Eltanin, 1974, USNM E33647 (2).

Description. Psolus species up to 45 mm long, 31 mm wide, 12 mm high (damaged paratype NMV F176181, preserved); oval to round in form with low profile, slightly raised anteriorly; clear demarcation between the body wall scales and oral and anal openings which are both concave when tentacles are retracted; tentacles 10, 8 large, 2 small ventrally; 5 medium-sized oral valves, sometimes composite, with small body wall scales encroaching up to half the length, both scales and valves are granuliform; large, irregular dorso-lateral scales up to 9 mm long with finely granuliform ‘beaded’ surface and typically grey to pale brown colouring with distinct white margins (preserved); 4 to 5 clearly defined rows of significantly smaller scales on the ventral margin, less than 1 mm in length, often conspicuous due to their central darker brown colouring; sole with inner paired to single or zig-zag rows of larger tube feet and a peripheral band of closely placed, smaller tube feet, bare mid-ventrally but tube feet extend variably at oral and anal ends onto the mid-ventral line.

Dorsal and lateral ossicles consist of multi-layered plates only, up to 1.68 mm long. Sole ossicles consist of oval to rounded bowls up to 160 µ m long and 128 µ m wide with heavily knobbed raised margins and rarer central knobs, rounded perforations are typically smaller towards the edges with 2–3 larger central perforations up to 48 µ m wide; knobbed perforated plates up to 160 µ m long and 120 µ m wide sometimes present. Majority of tentacle ossicles are thin, curved, irregular perforated plates with bluntly spinous edges; largest tentacle ossicles are thick and triangular, slightly curved with surface knobs and up to 424 µ m long and 256 µ m wide.

Colour (preserved). Pale to dark brown or grey dorso-lateral scales with distinct white margins.

Distribution. Australia, Macquarie I.; 108– 135 m.

Etymology. From the Latin par (like), with reference to its superficial similarity to P. antarcticus.

Remarks. Psolus parantarcticus sp. nov. was initially assumed to be P. antarcticus, which is also present on Macquarie Island at similar depths. Closer examination of preserved specimens revealed significant differences including encroaching body wall scales on oral valves for P. parantarcticus, along with bowl-like ossicles in the sole and multi-layered ossicles only dorso-laterally. P. parantarcticus is distinguished from other Australian Psolus species by a combination of: close peripheral series of distinctly smaller ventral tube feet; finely granuliform ‘beaded’ body wall scales; bowl-shaped sole ossicles; multi-layered ossicles only dorso-laterally.