Bathyceramaster amamiensis, 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 : 458-460

Bathyceramaster amamiensis n. sp. Mah & Fujita, 2024

FIGURE 3A–G

Etymology

The species epithet is named for the type locality in the Amami Trough.

Nomenclatural note: Toshihiko Fujita provided the specimen for this account and is credited as co-author for this species.

Diagnosis

Body stout, weakly stellate (R/r=1.82–2.2), broad weakly curved to straight interradii. Arms short, upturned. Plates tabulate, short, with surfaces covered by granules, 7–20, each polygonal to round in outline. Superomarginal plates wide to quadrate in shape, 30–34 per interradius, inferomarginals, 34–36, forming rolled or lateral facing margin, with superomarginal series sometimes obscured by overhang caused by abactinal surface. Furrow spines, 5 to 8, thick and blunt, triangular to polygonal or quadrate in cross-section, variably arranged in straight to convex series. Subambulacral spines, 4 to 8 total, in two series, 2 to 4 each row, three to four times as thick as furrow spines, with each row slightly shorter than the furrow spines.

Comments

A species distinguished primarily by abactinal granules of uniform size and shape, 15–20 per plate, with 30–34 marginal plates per interradius lacking pedicellariae on the actinal and adambulacral surface. This species and Bathyceramaster smithi share similar numbers of very similar shaped furrow spines and subambulacral spines as well as a “rolled” marginal edge.

Occurrence

Amami Trough, 946– 957 m.

Description

Body stout, weakly stellate ( R /r=1.82–2.2), broad weakly curved to straight interradii. Arms short, upturned ( Fig. 3A, E ).

Abactinal surface flexible, likely inflated with water in life, forming overhang onto superomarginal surface. Plates tabulate, short, with surfaces covered by granules, 7–20, each polygonal to round in outline ( Fig. 3B ). Disk and proximal plates larger with more discrete polygonal shapes becoming smaller, rounder distally along arms and especially interradially adjacent to superomarginal contact. Plates forming shallow fasciolar groove, especially well developed along radial papular regions on arms but nearly absent interradially adjacent to superomarginals. Plate bases polygonal. Radiating ossicles absent. Peripheral granules, four to ten, about two to three times larger than central granules, one to eight. Granules on each plate variable, with some showing more homogeneity; peripheral and central nearly identical in shape and size versus those which are more heterogenous with quadrate or polygonal peripheral granules surrounding the central granules. Granulated surfaces ranging from flat to convex. Granulation is more discrete and widely spaced on proximal disk and arm regions, becoming more densely packed interradially. Pedicellariae, small (length=~ 0.1 mm), paddle-shaped, most abundant interradially; absent on radial regions. Madreporite convex, polygonal to round in shape, shallow sulci, flanked by six to 12 plates. Granules becoming densely packed, obscuring plate boundaries around madreporite edge in one specimen. Papulae six per plate, one at each angle.

Superomarginal plates wide to quadrate in shape, 30–34 per interradius, inferomarginals, 34–36, forming rolled or lateral facing margin, with superomarginal series sometimes obscured by overhang caused by abactinal surface. Superomarginals distinctly offset with inferomarginals, forming strong zig-zag contact. Granules, 40–80 round to polygonal in shape, densely but evenly covering plate surface ( Fig. 3C ). Granules homogenous with no distinction between peripheral and central series. Fasciolar grooves between marginal plates also absent. Marginal plate granules identical to those on actinal surface. One or two plates per interradius with tiny pedicellariae, identical to those on abactinal surface. Marginal plate surfaces otherwise devoid of pedicellariae. Distalmost superomarginal plates with tumid, smooth bare spot. Terminal plate large, triangular with smooth surface.

Actinal surface large, four to six chevron plate series, but covered by densely arranged granules, round to polygonal, 20–40 per plate which obscure boundaries between plates ( Fig. 3D, E, F ). No distinctions between granules on peripheral and central regions. Granules become more densely arranged distally, adjacent to the inferomarginals. Pedicellariae, identical to those on abactinal, marginal surfaces, present on distal regions adjacent to inferomarginals ( Fig. 3F ).

Furrow spines, 5 to 8, thick and blunt, triangular to polygonal or quadrate in cross-section, variably arranged in straight to convex series ( Fig. 3F ). Furrow spines separated by discrete space from adjacent subambulacrals series. Subambulacral spines in two series, two to four each row, three to four times as thick as furrow spines, with each row slightly shorter than the furrow spines. Final row of subambulacrals, most similar to, nearly identical with granules on actinal surface. This distalmost row of subambulacral granules slightly more widely spaced relative to actinal granules.

Oral plates with nine to 13 furrow spines, blunt with rounded tip, similar in morphology to other furrow spines ( Fig. 3D ). Triangular to quadrate in cross-section. One spine similar to other furrow spines directed into mouth. Oral plate surface with eight thick spines (~twice width of subambulacrals), widely spaced, adjacent to subambulacrals. Remainder of oral plate covered by eight to ten paired thickened spines along boundary along contact between two halves of oral plate. Spines on oral plates widely spaced forming discretely different surface texture from actinal surface granulation.

Specimens Examined

Holotype. NSMT E-13674A CM0201 Amami Trough , 946–957 m. Coll. KT-93-0-9, St. AM-1, Coll. June 21, 1993, ORE beam Trawl 1 wet spec. R=5.3, r=2.4 .

Paratypes. NMST 13674B . CM0201 Amami Trough , 946–957 m. Coll. KT-93-0-9, St. AM-1, Coll. June 21, 1993, ORE beam Trawl, 2 wet specs. R=5.1, r=2.6; R=5.1, r=2.8. NMNS 13678 Sulu Sea, 1712–1840 m, Coll. KH-72-1, st. 14, May 27 1972 (1 wet spec. R =2.8, r=1.3 .

Figures

FIGURE 3. Bathyceramaster amamiensis Mah & Fujita n. sp. NMST E 13674A. A. Abactinal. B. Closeup abactinal plates. C. Abactinal-lateral view showing superomarginal and inferomarginal plates. D. Closeup oral view. E. Actinal. F. Closeup of adambulacral region, showing furrow and subambulacral spines. Scale bar=10.0 mm, A, E; Scale bar=3.0 mm: C, D; Scale Bar=2.0 mm: B,F.