Notioceramus abyssalis, Mah, 2023

Mah, Christopher L., 2023, New Genera, Species, and observations on the biology of Antarctic Valvatida (Asteroidea), Zootaxa 5310 (1), pp. 1-88 : 34-37

Notioceramus abyssalis n. sp.

FIGURE 10A–F

Notioceramus anomalus Mah 2011: 32 (part).

Etymology

The species epithet abyssalis is from the Latin for the abyss alluding to this species occurrence at great depth.

Diagnosis

Stellate species (R/r=2.0–2.6) interradial arcs weakly curved to straight. Arms tapering, elongate. Abactinal granules (3 counted along a 1.0 mm line at R=4.0) surface finely spinose (appearing “fuzzy”), forming continuous cover with plate boundaries remaining visible (versus those species with granular cover obscuring plate boundaries) ( Fig. 10A, B, C ). Marginal plates, 34–44, covered by spinose granules, 10–30, identical to those on abactinal surface. Actinal intermediate surface covered by cylindrical spines with blunt spinose tips. Furrow spines 3, subambulacral spines 2, one short and one large ( Fig 10D, F ).

Comments

Notioceramus abyssalis n. sp. is one of two Notioceramus species collected from a substantially deeper depth (2782–3876 m versus 73–1120 m) than Notioceramus anomalus as outlined by Fisher (1940) and A.M. Clark (1962). Depth occurrence is comparable to if not potentially deeper than that of Notioceramus neillae n. sp.

As compared with Notioceramus anomalus , granules of Notioceramus abyssalis are much and are much more densely packed (three granules along a 1.0 mm line at R=4.0 cm) compared with the N. anomalus as outlined by Fisher (1940) which shows only a single coarse granule present on a 1.0 mm line (at R=4.0 cm). Furrow spine number in this species is greater (n=3) versus two in N. anomalus . Notioceramus neillae n. sp. also displays pointed spines on its actinal plate surface whereas spines of N. anomalus are thick, blunt granules.

Occurrence

Off South Georgia Island, South Orkney Islands, Scotia Sea, South of Burdwood Bank, Elephant Island. 2782– 3876 m.

Description

Body stellate (R/r=2.0–2.63), arms tapering, weakly elongate, termini upturned. Interradial arcs weakly curved to straight. Disk strongly arched ( Fig 10A, B, C ).

Abactinal surface composed of plates, abutted, flat, polygonal in outline forming relatively thin surface. Abactinal plates extend along surface to arm tip, series reducing to two or three near arm tip. Granules present as dense covering over plate surfaces obscuring boundaries between plates ( Fig. 10B ); granular cover extending without interruption onto superomarginal plates ( Fig. 10C ). Individual granules with finely spinose surface, yielding a “fuzzy” appearance. Approximately three granules present along a 1.0 mm line, homogeneous in size, approximately 10–40 per plate. Madreporite polygonal in shape, convex sulci well-developed ( Fig. 10A . 1 ). No pedicellariae observed.

Superomarginals, inferomarginals, approximately 34–44 from armtip to armtip (at R=1.9 to 3.8, respectively). Each marginal plate quadrate in shape, wider distally, but more nearly equidimensional proximally ( Fig. 10C ). Each plate covered by coarse granules, 10–30 (most with about 20), slightly coarser than those on abactinal surface. Only about two granules along a 1.0 mm line. Granular cover is continuous on most plates and obscures boundaries around marginal plates. Some individuals (e.g., USNM E35072) display superomarginals with the central region, weakly convex, smooth and devoid of granules, a bald surface. Terminal plate large, round.

Actinal surface composed of approximately three chevron series, largest adjacent to adambulacral plate series, becoming more irregular and incomplete adjacent to inferomarginal contact. Surface with one to six, mostly four to six, widely spaced blunt pointed spines ( Fig. 10D, E ). Plates with approximately one to two larger spines surrounded by widely spaced three to six shorter spines.

Furrow spines, cylindrical in shape, mostly three, blunt tipped, round in cross-section spines similar to those on actinal plate surface. Subambulacral spines in three irregular series, proximalmost with two spines, one identical with short actinal spines and one large, blunt spine, approximately twice as thick and twice as long as each furrow spine ( Fig. 10D, F ). Further subambulacral spines, three short and blunt on actinal/adambulacral contract. Oral plates with five furrow spines similar in size, thickness to other furrow spines. Each plate covered with two to four thick, short, blunt spinelets.

Material Examined

Holotype. USNM 1081973 , South of South Georgia Island, Scotia Sea. −58.075, −37.783, 3166–3255 m. Coll. R/V Eltanin, 30 Aug. 1963. 1 dry spec. R=4.3 r=2.2.

Paratypes. USNM E35072 , Off South Georgia Island.−56.25, −38.567, 3520– 3136 m. Coll. R/V Eltanin, 1 Mar. 1966. 1 dry spec. R=2.9 r=1.1.

USNM E53633 , South of Burdwood Bank, Scotia Sea , −55.025, −58.817, 2782–2891 m. Coll. R/V Eltanin, 4 Dec. 1962. 1 dry spec. R=2.7 r=1.4.

USNM E53634 , SE of Burdwood Bank , Scotia Sea. −55.12, −55.83, 2873–2891 m. Coll. R/V Eltanin, 22 Dec. 1962. 1 dry spec. R=2.6 r=1.1.

USNM 1082951 , Scotia Sea. 58°06’S, −58.133, −44.858, 2800 m. Coll. R/V Eltanin, 15 Feb. 1963. 1 dry spec. R=3.3 r=1.6.

USNM 1084426 , South of South Georgia Island, −56.875, −37.542, 3138–3144 m. Coll. R/V. Eltanin, 28 Aug. 1963. R=2.5 r=1.2.

USNM 1018753 , South Georgia Island, Scotia Sea, −55.025, −38.167, 2196–2379 m. Coll. R/V Eltanin, 25 Aug. 1963. 1 dry spec. R=4.3 r=1.7.

USNM 1082949 , South Georgia Island, Scotia Sea , South Atlantic Ocean . −55.092, −39.842, 2886–3040 m. Coll. R/V Eltanin, 8 Feb. 1966. 21 dry specs. R=3.6 r=1.8, R=3.6 r=1.8, R=4.0 r=2.0, R=3.8 r=2.0, R=3.5 r=1.7, R=3.6 r=1.5, R=3.6 r=1.8, R=4.2 r=1.8, R=3.9 r=1.9. R=3.9 r=1.9, R=2.0 r=0.9, R=2.0 r=0.9, R=4.0 r=2.0, R=3.5 r=1.9, R=4.2 r=2.2, R=4.2 r=1.9, R=3.2 r=1.4, R=3.6 r=1.8, R=3.6 r=1.8, R=3.6 r=1.6, R=3.7 r=2.2.

USNM 1086348 , SW of South Georgia Island, Scotia Sea , South Atlantic Ocean . −55.108, −44.367, 3623–3714 m. Coll. R/V Eltanin, 12 Feb. 1963. 3 dry specs. R=3.4 r=1.5, R=3.7 r=1.5, R=2.7 r=1.3.

USNM 1091144 , East of South Georgia Island, Scotia Sea , South Atlantic Ocean , −56.033, −33.967, 3138– 3239 m. Coll. R/V Eltanin, 8 Sept. 1963. 2 dry specs. R=~3.8 r=1.7 arm tips broken, R=3.3 r=1.3.

USNM 1091172 , South Orkney Islands, Scotia Sea. −59.975, −49.233, 3819–3876 m. Coll. R/V Eltanin, 7 March 1963. 1 dry spec. R=3.1 r=1.3.

USNM 1121093 , SW of South Georgia Island, Scotia Sea , −62.692, −56.183, 3486 m. Coll. R/V Eltanin, 13 Feb. 1963. 2 dry specs. R=2.0 r=0.9, R=1.5 r=0.6.

CASIZ 162494 , Elephant Island. −60.655278, −53.783333, 2896 m. Coll. R. Mooi & S. Lockhart aboard PFS Polarstern, 2 Feb. 2002. 1 wet spec. R=3.6 r=1.7. 1 wet spec. R=3.0 r=0.9.

NHM- (number not provided), South Sandwich Island , Scotia Sea. Coll. British Antarctic Survey , 30 Jan. 2010, station JC42-F-0381. 1 wet spec.

Figures

FIGURE 1. Astrotholus antarcticus (Fisher 1940) CASIZ 175766. A. Abactinal. B. Closeup of abactinal surface showing plates and granules. C. USNM 1573471, Distal armtip abactinal-lateral view showing superomarginal plates. D. Oral view, close showing oral plates/spines, furrow spines, accessories. E. Oral view showing general morphology. Astrotholus antarcticus (Fisher, 1940). F. Actinal-lateral view showing actinal plates, spinelets, inferomarginal plates.

FIGURE 10. Notioceramus abyssalis n. sp. USNM 1081973. Holotype. A. Abactinal surface. A.1. Madreporite. B. Closeup showing granules. C. Abactinal-lateral view showing marginal plates and granular cover. D. Oral view closeup showing mouth, general details. E. Actinal view. F. Closeup of actinal intermediate surface.