Ceramaster pointsurae, Mah, Christopher L., 2016

Mah, Christopher L., 2016, Deep-sea (> 1000 m) Goniasteridae (Valvatida; Asteroidea) from the North Pacific, including an overview of Sibogaster, Bathyceramaster n. gen. and three new species, Zootaxa 4175 (2), pp. 101-141 : 114-116

Ceramaster pointsurae n. sp.

Figure 4 A–D

Etymology. This species is named in honor of the Moss Landing Marine Laboratories research vessel R/V Point Sur which was retired from service in 2014.

Taxonomic comments. This species shows affinities between both Ceramaster and the newly established Bathyceramaster n. gen. described herein. The prominent superomarginal frame with the abactinal-facing is argued as the primary synapomorphy for this species’ placement within Ceramaster rather than Bathyceramaster which shows a more flush and lateral-facing marginal series. However, because of the likely problematic nature of Ceramaster as outlined here and in Mah (2011) assignment of this species to Ceramaster should be considered a hypothesis for future testing.

Morphological characters which set this species apart from the others include a more strongly stellate shape (R/r=1.6–2.0 at R=1.8), spiny to granulose accessories present on each weakly tabulate abactinal plate, the large smooth, bald surface present on each superomarginal and inferomarginal plate, shape of the superomarginal plates, and the joined penultimate superomarginals abutting over the midline of the arm. Nearly all of the other known North Pacific Ceramaster species possess abactinal granules which are primarily angular in outline, a more strongly pentagonal body shape (1.3–1.6 at R=1.5 and greater), with pedicellariae present or absent on the marginal plates (always absent in Ceramaster n. sp.). Other potentially variable characters include the much smaller size in all known specimens of Ceramaster n. sp. and the much deeper known bathymetric occurrence (1730–1975 m) versus the other species which occur in a much shallower bathymetric range (intertidal- 1811 m).

A deep-water Ceramaster species from this region and in proximity to the other North Pacific shallow water Ceramaster species suggests a parallel relationship to Hippasteria tiburoni with regard to the shallow-water species of Hippasteria in the North Pacific (Mah et al. 2014).

In situ observations. All individuals of Ceramaster pointsurae n. sp. were observed in situ sitting on rocky substrate, composed primarily of basalt. Disks were not inflated.

Description. Body stout, stellate (R/r=1.6–2.0). Interradial arcs weakly rounded ( Fig. 4 A).

Surface sunken below plane of superomarginal series. Abactinal plates round to polygonal in outline, covered by seven-30 (mostly 10–25) granules. Six to 20 rectangular-oblong granules form discrete periphery surrounding one to eight round central granules on radial plates. ( Fig. 4 B). Interradial plates with more rounded peripheral granules forming denser aggregations adjacent to the contact with the inferomarginals. Fasciolar grooves and papular pores well-developed over radial region ( Fig. 4 A,B). Enlarged primary plates, about twice the size of others, present on disk in each interradius, especially on smallest individual (R=0.9). Abactinal plates extend only approximately halfway up arms, terminating just before the superomarginals abut over midradius. Madreporite pentagonal, flanked by four or five plates. Pedicellariae on abactinal surface not observed.

Marginal plates wide, forming a thickened frame around body. Superomarginals and inferomarginals number 10–16 (armtip to armtip) with 1:1 correspondence interradially becoming more offset distally. Both series of marginals with large, discrete smooth, round to more quadrate, bald patches ( Fig. 4 A,B). Bald patches smaller interradially (covering only about 75% of plate surface) becoming larger and covering more of the plate surface distally, becoming almost completely smooth and bald adjacent to the terminal plate. Surface becomes more strongly convex distally, especially adjacent to the terminal ( Fig. 4 B). Granules, 20–60 covering remainder of plate round to polygonal, densely packed becoming fewer distally as bald patch becomes larger. Peripheral granules, approximately 10–15 per side, about 40–60 total per plate. Distalmost two pairs of superomarginal plates abut over midradius with third pair, partially in contact in the largest specimen. Shallow fasciolar groove present between marginal plates.

Actinal surface flat composed of two to four series of polygonal to irregular=shaped plates in a chevron-like pattern. Surface covered by round to angular granules which obscure boundaries between plates ( Fig. 4 C). Furrow spines slender, three to four, mostly four arranged in straight to palmate pattern ( Fig. 4 D). Two thick but pointed subambulacral spines, approximately twice as thick as a single furrow spine, set off from furrow spines by discrete space. A second row of subambulacral spines sits adjacent to the first series, less than half the height but closely resembles angular granules on actinal surface. Oral furrow spines, six to seven with one spine, paired with another spine on the paired oral plate, directed into the mouth. Oral plate surface with eight to 12 spines with six paired spines on border in contact with the adjacent, paired oral plate.

Color in life of this species was off-white.

Material. Holotype: USNM 1407942 President Jackson Seamount B, North Pacific , 42.83314, -128.16122, 1975.7 m . Coll. D. Clague, MBARI D81-A10. 1 wet spec. R=1.8, r=1.0, Paratypes: USNM 1407943 President Jackson Seamount C, North Pacific , 42.740027, -128.09826, 1742.1m . Coll. D. Clague, MBARI, D82-A3. 1 wet spec. R=1.0, r=0.6; USNM 1407944 President Jackson Seamount C, North Pacific , 42.739989, -128.09716, 1730.1 m . Coll. D. Clague, MBARI, D82-A6, 1 wet spec. R=1.2, r=0.6.

Figures

FIGURE 4. Ceramaster pointsurae n. sp. Holotype. USNM 1407942. Scale bar = 3.0 mm. A. Abactinal surface. B. Closeup of abactinal surface superomarginal plates. C. Actinal surface. D. Closeup of actinal surface, adambulacral furrows.