Pillsburiaster aoteanus McKnight, 1973

(Figures 16 A–D)

McKnight, 1973: 180, fig. 5; A.M. Clark, 1993: 276, H.E.S. Clark in Clark and McKnight 2001: 100 (as P. aoteanus) McKnight, 1973: 185, fig. 7; 1993: 169, 185; A.M. Clark 1993: 277 (as P. singletoni)

Distribution. New Zealand area. 120–1573 m.

Material examined. USNM 1100852 Campbell Plateau, New Zealand. 49°13’30”S, 171°30’06E, 260 m. Coll. R/V Kayo Maru, 21 Dec. 1970. (1 dry spec. R=6.3, r=4.0); USNM 1100862 Campbell Plateau, New Zealand. 48°40’ S, 170° 48’30”, 814 m. Coll. NIWA, 20 Jan 1965. (2 dry specs. R=5.1, r=3.7; R=3.2, r=2.3). Description. Body outline pentagonal to weakly pentagonal (R:r=1.3–1.5) (Fig. 16 A). Body flat, thickened.

Abactinal plates irregular to round in outline with larger plates proximally becoming smaller distally, adjacent to contact with superomarginal series, each plate covered by granules. Abactinal granules, coarse, spherical, round to quadrate in outline, 7–25 per plate. Granules crowded proximally becoming more evenly distributed distally (Fig. 16 A, B). Granules size larger proximally but smaller adjacent to contact with superomarginal series becoming denser and nearly identical in size to granules on marginal plate series. Papulae, 4–6 surround each abactinal plate, cover abactinal surface but absent from interradial regions. Fasciolar grooves absent, plates abutting.

Marginal plate series with approximately 1:1 correspondence between superomarginal and inferomarginal series, becoming slightly offset distally as arm becomes upturned (Fig. 16 D). Each plate convex in cross-section, forming distinct border around abactinal, actinal surface. Superomarginal plates wide, number 30 at R=6.3 (22 at R=5.1). Granules 120–180 in number, each with rounded, concave surfaces, evenly covering surface. Larger granules present on lateral surface with smaller granules adjacent to abactinal surface, inferomarginal series. Bald area, wide, raised relative to surface of plate, present on each superomarginal plate. Inferomarginal plates wide, 32 in number at R=6.3 (24 at R=5.1), covered by evenly distributed granules, round.

Granular covering on inferomarginal plates is complete in larger individuals (R>5.0) but a bald patch is present in smaller specimens (R=3.2). No discrete granular series (e.g., peripheral series) present.

Actinal surface each angular to quadrate-triangular to irregular in shape. Actinal plates in five to six distinct chevron series. Actinal plate series arrangement becoming more irregular proximal to inferomarginal plate series (Fig. 16 C). Each plate covered by round granules, 4–50 in number, evenly to widely spaced over actinal plate surface. Granules larger proximally, becoming smaller and denser adjacent to contact with inferomarginal plates.

Adambulacral plates wide, separated from actinal plate series by discrete gap. Furrow spines five to six, (four distally) crowded on plate, each relatively thick, rounded-quadrate to triangular in cross-section, Subambulacral spines granular, thick, blunt, in two to three irregular rows of four each, round in outline. Subambulacral spines approximately half to 40% of length, but similar in thickness to furrow spines, distinctly larger from actinal granulation. Smaller irregularly sized granules present among subambulacral granules. Oral plates with nine to ten furrow spines, with one enlarged spine, triangular in cross-section projecting into mouth. Oral plates on each interradius with prominent gap separated by connective tissue. Each gap on oral plate bordered by 10–11 granular spines. Each half oral plate covered with 10–15 additional granules, rounded to prismatic in shape. A pair of enlarged spines, triangular in outline, present on oral plate surface, in addition to enlarged furrow spines projecting in mouth. Total of approximately 50 total granules, quadrate to angular, on each oral plate pair per interradius (i.e., ~25 per plate). Granules on oral plate distinctly larger, more evenly spaced then those on other actinal intermediate plate. Oral plates separated from actinal plates by discrete bare gap between plates.