Notioceramus neillae Mah 2023, n. sp.

Notioceramus neillae n. sp.

FIGURE 11A–F

Etymology

The species epithet is named for Ms. Kate Neill, echinoderm researcher at the New Zealand Institute of Water and Atmosphere who has been instrumental in repatriation of US Antarctic Research Program specimens to the NMNH.

Diagnosis

Body stellate, arms tapering, triangular (Fig. 11A). Superomarginal plates with bald spot, variably small (<25% of total surface) to near entirety of plate surface (Fig. 11B, C, D). Superomarginal plates form distinct convex curvature onto lateral abactinal surface. Furrow spines two or three (Fig. 11F).

Comments

This is a second deep-water Notioceramus species, which appears to share more characters in common with Notioceramus anomalus. This latter, shallower species displays smooth, spherical granules on the abactinal and marginal plates as well as on the tips of actinal spines; in contrast, arms of Notioceramus neillae n. sp. are less robust and granules only finely spinose. Granules and actinal spination more weakly developed arms compared to either Notioceramus anomalus or Notioceramus abyssalis n. sp.

Occurrence

Weddell Sea, Antarctic Peninsula, 2324–3175 m.

Description

Body stellate (R/r=2.2–2.3), arms tapering, outline triangular, disk thick, strongly arched, Interradial arcs curved (Fig. 10A).

Abactinal plates quadrate to irregular in shape, forming abutted mosaic, each with strongly tumid or convex surface (Fig. 11B). Surface of each plate covered by round granules, 2 to 12, mostly 6 to 10. Two granules counted along a 1.0 mm line. Plates heterogeneous, angular to round. Plates tend to be largest on disk with smallest distally along arms. Carinal series indistinct weakly defined, composed of irregular plates from disk to arm tip. Fasciolar grooves shallow but distinct. Madreporite oblong, round, flanked by two granule-covered plates (Fig. 10A. 1). Papular pores individual, discrete, paired along carinal plates on proximal arm region. No pedicellariae observed.

Marginal plates 34 per interradius (arm tip to arm tip) with superomarginals slightly offset from inferomarginals forming a zigzag pattern at the contact between them. Superomarginals wide, especially interradially, forming distinct concave series onto the lateral edge of the disk’s abactinal surface (Fig. 11A, C). Spherical coarse granules, 10–50, typically numbering about 30–40. As with the abactinal granules, these are approximately 2 along a 1.0 mm line (at R= 3.9 cm). Superomarginals with a variably large bald, convex patch. Interradially bald patch absent from at least one plate but on others, it is small, round and irregularly shaped becoming larger on the arms becoming quadrate in shape, occupying entire central surface of superomarginal plates (Fig. 11C, D). Superomarginal plates, granulate, 20–30 present around plate periphery. Inferomarginal plates interradially wide becoming more quadrate distally (Fig. 11C). Inferomarginals follow convex curvature of superomarginal plate series onto lateral surface. Granules of identical size to those on abactinal and superomarginal surfaces, approximately 40–60, approximately 20–30 forming periphery around edge. Terminal plates large, shield shaped, approximately twice the size of adjacent superomarginals.

Actinal plates in approximately 4 chevron-like series, plates quadrate. Surface of each plate with coarse, evenly spaced granules, 4 to 8 (Fig. 11C). Plates with shallow pronounced fasciolar groove. No pedicellariae observed.

Furrow spines 2 or 3, thick, oval in cross-section, aligned in series.Three furrow spines on proximal adambulacral plates (Fig. 11F). Subambulacral spines at oblique angle to furrow spines, set off from furrow spines by distinct gap, two or three, thick, each quadrate in cross section, becoming more pronounced distally. Oral plates with four furrow spines, one larger spine projecting into mouth (two per interradius), Furrow spines thick and oval in cross-section (identical to other furrow spines) the main oral spine triangular in cross section. Oral plate surface with 5 thick blunt spines, quadrate in cross-section. Fissure between paired oral plates distinct.

Based on notes included with USNM 1664380 this species was “brownish yellow” when collected.

Holotype. USNM 1018751, Southeast of Joinville Island, Antarctic Peninsula, Weddell Sea, −64.092, −52.475, 2324–2342 m. Coll. R/V Eltanin, 16 March 1964. 1 dry spec. R=3.9 r=1.8.

Paratypes. USNM 1664380, South of Coronation Island, South Orkney Islands, Scotia Sea, −62.1883, −42.7217, 1228–1400 m. Coll. R/V Islas Orcadas, 20 Feb. 1976. 2 dry specs. R=3.3 r=1.5, R=3.3 r=1.4.

USNM 1121183, Southern Ocean, Antarctica, −68.092, 173.683, 2608–3175 m. Coll. R/V Eltanin, 12 Jan. 1967. 1 dry spec. R=1.4 r=0.6.