Pillsburiaster hyugaensis Mah & Fujita, 2024

Mah, Christopher L., 2024, New genera and species of deep-sea Goniasteridae (Asteroidea) from the North Pacific, Zootaxa 5543 (4), pp. 451-500 : 476-479

Pillsburiaster hyugaensis Mah & Fujita n. sp.

FIGURE 8A–F

Etymology

This species is named for the type collection locality, the Hyuga Basin. Nomenclatural note: Toshihiko Fujita provided the specimen for study and is co-author of this species.

Diagnosis

Body weakly pentagonal, R/r=1.67, interradial arcs curved to straight. Abactinal plates convex, covered with large, coarse, round granules (two to three granules per 1.0 mm), two to ten. Superomarginals 28 from armtip to armtip, both marginal plate surfaces completely covered by coarse granules, approximately 2 to 3 granules per 1.0 mm count, 200–300 total granules per surface. Actinal plates covered by 20 to 80 coarse, round granules with approximately five to 40 forming the perimeter of each plate. Furrow spines 7 to 10, each similar or identical in size and shape, in a straight to curved arrangement. Subambulacrals with blunt tips, round to triangular in cross section, in three ordered to irregularly ordered rows.

Comments

This species is distinguished from other Pillsburiaster species in showing 7 to 10 furrow spines. All other known species possess seven or fewer furrow spines. Most possess five to seven with some species, such as the Pacific P. ernesti or the South Atlantic P. calvus with four to five or two to three furrow spines per plate, respectively. This species also varies from other known species in that it lacks a bare convex patch on the superomarginal surface, which is completely covered by granules.

Although this species occurs within the known depth range for Pillsburiaster (339–2149 meters) the specimen was collected from relatively shallow water relative to other known species. This also represents the northernmost known occurrence of Pillsburiaster w ith most other species occurring at or south of the equator ( Clark & Downey 1992; A.M. Clark 1993).

Description

Body weakly pentagonal in shape ( R /r=1.67). Interradial arcs curved to straight ( Fig. 8A, E ).

Abactinal surface level with superomarginals (dry specimen). Abactinal plates convex, covered with large, coarse, round granules (two to three granules per 1.0 mm), two to ten ( Fig. 8B, C, D ). Individual plates abutting one another. Each plate surrounded by two to four large, prominent papular pores distributed over radial and interradial regions. Papulae absent distally along edge of superomarginals. Carinal plates indistinct. Abactinal plate size relatively uniform, weakly developed fascioles present. Plate size smaller adjacent to the superomarginal contact. Madreporite with deep sulci flanked by 10 plates. Abactinal plates largest towards disk center becoming smaller towards disk edge adjacent to superomarginals.

Superomarginals 28from armtip to armtip with1:1 correspondence to inferomarginals( Fig.8D ).Superomarginals with rounded edge with weakly quadrate outline. Both superomarginals and inferomarginals with largest plates proximally (i.e., interradially) becoming smaller distally. Superomarginal plate surface completely covered by coarse, round granules (two granules per 1.0 mm) similar in overall appearance to those on abactinal plates ( Fig. 8B, D ). No bare areas. Granules distribution dense but evenly spaced. Approximately 200–300 granules cover each superomarginal and inferomarginal plate surface, with approximately ten granules per side (~40 per plate). Contact between abactinal superomarginal facing and disk is concave. Superomarginal–inferomarginals with shallow fasciolar groove between them. Inferomarginal contact with superomarginals becomes more zig-zag in pattern among distal superomarginal/ inferomarginal plate pairs but more straight and 1:1 interradially. Contact between inferomarginals and actinal intermediate region, is straight to weakly convex. Terminals horseshoe shaped, larger than both adjacent abutting superomarginals.

Actinal intermediate area with approximately eight to 10 weakly developed chevrons ( Fig. 8E ). Plate series and individual plate shape well-developed and shape homogeneous adjacent to furrow spines becoming more irregular in both shape and order farther from the furrow. Actinal plate shapes vary, ranging from quadrate, hexagonal to irregularly polygonal. Those plates at center of intermediate area smallest and most irregular. Each actinal plate covered by 20 to 80 coarse, round granules with approximately five to 40 forming the perimeter of each plate. Granules identical in size and overall appearance to those on the abactinal surface.

Furrow spines 7 to 10, each similar or identical in size and shape, in a straight to curved arrangement ( Fig. 8F ). Each spine blunt, oval to quadrate in cross-section. Proximalmost spines approximately half the length of the other furrow spines and slightly set apart from other furrow spines. Subambulacral spines with blunt tips, round to triangular in cross section, in three ordered to irregularly ordered rows. First row of subambulacral spines, four to eight, adjacent to furrow but set off by discrete space, only about 50% of height of other furrow spines. Second and third subambulacral rows low, closer in elevation to granules present on actinal intermediate region but approximately twice as thick, arranged in regular and irregular rows.

Oral region with furrow spines six (distally) to nine (proximally), and large oral spine, triangular in cross-section projecting into mouth ( Fig. 8E ). These spines consistent in appearance with those mentioned above for furrow spines.

No pedicellariae observed on abactinal, marginal or actinal surfaces.

Material Examined

Holotype. NSMT E-11392 (CLM 1159) Hygua Basin , 32º35.6’N,132º13.9’E to 32º34.6’N, 132º12.0’E, 790–808 m, Coll. R/V Tansei-Maru. KT-99-18, St. BT-1, 16 Dec. 1999. 1 dry spec. R=9.2, r= 5.5 cm .

Figures

FIGURE 8. Pillsburiaster hyugaensis Mah & Fujita n. sp. NSMT E-11392. Holotype, A. Abactinal B. Abactinal-lateral view. C. Abactinal Closeup showing coarse granules. D.Abactinal-lateral view showing surface superomarginal plates. E. Actinal. F. Adambulacral plates showing furrow and subambulacral spination. Scale bar=20 mm, A, E; Scale bar=3.0: B, D; Scale bar=2.0 mm: C, F.