Alloceramaster minus, Mah, 2025

Alloceramaster minus View in CoL nov. gen, nov. sp.

Figures 5A–E

Material Examined. Holotype. WAM Z110126 About WAM . Gascoyne Marine Reserve , 164 km NW of Kurabi Point, 20º 50' 3.4332" S, 112º 51' 52.9524" E, 1088 m. Coll. B. Alvarez, K. M. Naughton, K. Moore, C. Unteidt, aboard RV Investigator CSIRO barcode 10052895. 1 wet spec. R = 1.7 r = 0.9 GoogleMaps

Paratype. WAM Z110133 About WAM . Gascoyne Marine Reserve , 164 km NW of Kurabi Point, 20º 50'03.4332" S 112º 51' 52.9524" E, 1088m, Coll. B. Alvarez, K. M. Naughton, K. Moore, C. Unteidt, aboard GoogleMaps RV Investigator CSIRO 10052998, 1 wet spec . R = 0.8 r = 0.6.

Etymology. The species epithet minus refers to the Latin for bare or smooth, alluding to the absence of granules on the superomarginal plate surface.

Diagnosis. Body stout, shape pentagonal to weakly stellate, (R/r = 1.3–1.8), arms short, blunt. Interradial arcs weakly curved to straight. Abactinal surface covered by dense cover of granules. Radial areas with fasciolar grooves, bearing widely spaced rectangular to broadly trapezoidal peripheral granules versus polygonal to round central granules, these differing from those on interradial areas which show identically shaped peripheral and central granules. Superomarginal plates 10 per interradius. Penultimate superomarginals similar in size to adjacent superomarginals. Superomarginal surface with large, bald, smooth surface. Inferomarginal plates similar overall to superomarginal plates, but with a rounded-quadrate bald patch on actinal surface, while remainder of surface covered by 20– 130 granules. Furrow spines 6 to 8, mostly 6 with highest number of spines on proximalmost adambulacral plates. Subambulacral spines 3, blunt, 2 to 3 times the thickness of the furrow spines. Pedicellariae, when present with forceps-like valves present with abundance on abactinal surface.

Comments. Alloceramaster minus n. sp. shares with A. leios n. sp. the presence of a prominent bald patch or surface ( Fig. 5A, C) on the superomarginal plate surfaces and marginal plate number per interradius differ, although both characters may vary based on size. There are an abundance of forceps-like pedicellariae on the abactinal surface of A. minus . This species also displays some resemblance with A. grenadensis in that it has round to polygonal abactinal plates on its papular region with triangular to trapezoidal-shaped peripheral granules.

Occurrence/Distribution. Gascoyne Marine Reserve, Western Australia, Indian Ocean , 1088 m .

Description. Body stout, shape pentagonal to weakly stellate, (R/r=1.3–1.8), arms short, blunt. Interradial arcs weakly curved ( Fig. 5A, D).

Abactinal plates with low tabulate plates over radial regions where papulae are present, abutted abactinal plates centrally and interradially ( Fig. 5B). Non-radial plates hexagonal to irregularly polygonal in shape, covered by granules, round to polygonal, close set, homogeneous in size and shape, but discretely separated into peripheral and central areas. Granules form continuous cover, approximately 5 to 6 counts along a 1.0 mm line, totalling 8 to 30 per plate ( Fig. 5B). Radial plates, approximately 9 plates per arm with more widely spaced peripheral granules, up to 20 granules densely arranged on plate surface on a convex surface. Shallow fasciolar grooves present around these radial tabulate plate regions ( Fig. 5B). Pedicellariae with narrow forcep-like valves, approximately 15–25 per interradius. Madreporite triangular in shape, on raised plate, flanked by three plates, and approximately 18–20 granules.

Marginal plates 10 per interradius, arm tip to arm tip (4 to 5 per arm side), 2 superomarginals abutted in full contact along midline at arm tip ( Fig. 5C). Superomarginal plates round in cross-section with strongly convex surface along abactinal-lateral angle, quadrate in overall shape. Central surface of superomarginal plates with a large, smooth and bare quadrate region ( Fig. 5A, C). Lateral surface of superomarginals covered by small, round granules, 60–70, widely spaced. Inferomarginal plates similar overall to superomarginal plates, but with a rounded-quadrate bald patch on actinal surface, while remainder of surface covered by 20–130 granules, evenly spaced. Some superomarginal plates show signs of damage and double-plate growth. No pedicellariae observed. Terminal plate round, with smooth surface.

Actinal intermediate region with two full series in chevron formation, with irregularly arranged plates adjacent to inferomarginal contact. Individual plates quadrate in shape. All plates covered by granules, 9 to 20, mostly 8–15, round to polygonal ( Fig. 5E). More widely spaced proximally becoming more closely arranged distally adjacent to contact with inferomarginal plates.

Furrow spines 6 to 8, mostly 6 ( Fig. 5E) with highest number of spines on proximalmost adambulacral plates. Spines blunt with rounded tips, in weakly palmate formation. Subambulacral spines 3, 2 distalmost enlarged, proximalmost spine smallest set off from furrow spines by a discrete space. Subambulacral spines thick, approximately 2 to 3 times the thickness of the furrow spines, blunt tips, similar in height, the smallest of these spines approximately 50% of the height of the other subambulacral spines. Remainder of adambulacral plate covered with blunt, thick, granules, approximately half the height of the subambulacral spines, similar in stature to granules on the actinal surface. These granules widely spaced with a single row, composed of four granules at contact with actinal plates. Oral plates with 6 furrow spines, triangular in cross-section with blunt tips and a seventh spine projecting into the mouth from the tip of each oral plate (two in each interradius). Oral plate with 6 to 8 pairs of thick granules ( Fig. 5E), each triangular in cross-section with blunt tips on either side of the diastema between the paired oral plates. A single pedicellariae, forceps-like valves, on one of the proximal adambulacral plates adjacent to the oral region with narrow valves ( Fig. 6E).