Pillsburiaster indutilus McKnight 2006

Pillsburiaster indutilus McKnight, 2006

McKnight, 2006: 102

Distribution. Christabel Seamount to the south of New Zealand. Also, Gothic Seamount, northeast of the Chatham Islands. 968–1140 m.

Material examined. None.

Description. (from McKnight, 2006). Body pentagonal, R/r=1.57. Interradial arcs weakly curved with arms tapering.

Larger abactinal plates round to ovoid. Secondary plates angular, present proximal on disk and flanking inner end of carinal series. Carinal series ovoid, wider than long. On either side of carinal row are three further regular series of rounded plates; interradial plates more variable in shape, decreasing in size towards contact with superomarginal series. Abactinal plates slightly raised, each with a marginal series of small granules, weakly spaced. Plate surface with granules rounded, deciduous, often slightly flattened and weakly slightly spaced apart. Peripheral granules equal in size to those on the plate center. Many plates with granules lost, leaving distinct depressions. On these plates, small “crystal bodies” are apparent. Carinal plates surface with approximately 20 peripheral and 20 internal granules. Papulae present over radial regions. Pedicellariae, small spatulate, with flattened valves each with a curved tip, present on several plates. Where pedicellariae have been removed, a distinct slit, surrounded by a narrow groove is present.

Superomarginals 14 in each interadial arch, with three pairs of distalmost superomarginals abutting over midline, tumid on abactinal surface, wider then long throughout. Superomarginals with embedded hemispherical granules scattered along surface. Granules absnet from distal plates on abactinal and lateral surfaces. Marginal plates a complete border of small, flattened granules. Inferomarginals wider then long, save for distalmost plates which are longer then wide. Both marginal granules and embedded deciduous granules forming dense cover interradially becoming sparser distally. Terminal plate rounded and conical with a pointed pointed tubercle present. Other marginals with a small pit.

Actinal plates arranged into six chevrons with the innermost extending to proximal end of third inferomarginal from armtip. Actinal plates flat, rectangular, adjacent to adambulacrals but four-sided to round interradially. Actinal plates covered by hemispherical granules, approximately 30 on larger plates. No pedicellariae observed.

Adambulacral plates subrectangular and wider then long. Furrow spines five (rarely six), each with blunt, rounded tip, oval in cross section. Proximal and distal spines are shorter then those medially. Subambulacral spines, blunt, three or sometimes four in three slightly spaced rows. Where four are present, proximalmost is smallest, middle row with three to four shorter spines; outer row with three to five granules. Exceptionally, a pedicellaria is present. Distal plates with a single enlarged, longer and thicker subambulacral spine.

Oral plates triangular, furrow spines nine to 10, more elongate then adambulacral furrow spines, angular in cross-section, blunt. Proximal spine longer then others. Suboral spines five to six, shorter, and angular parallel the furrow series with a further three to four short spines continuing along the margin adjoining the first adambulacral and proximal actinal plate. Short spines or granules, seven to eight, angular, forming a row along median suture. Three to four other granules present between this row and that adjacent to the furrow spines.