Calliaster thompsonae H.E.S. Clark & McKnight 2001

Mah, Christopher L., 2018, New genera, species and occurrence records of Goniasteridae (Asteroidea; Echinodermata) from the Indian Ocean, Zootaxa 4539 (1), pp. 1-116 : 26-28

Calliaster thompsonae H.E.S. Clark & McKnight 2001

Figure 8 A–E

Clark, H.E.S. & McKnight 2001: 25

Diagnosis. Species with triangular tapering arms, abutted superomarginal plates present along the arm ( Fig. 8A ), wide superomarginal plates ( Fig. 8C ), large conical spines present on the abactinal and marginal plates ( Fig. 8A, C ), adambulacral plates rectangular, weakly convex actinal plates and six to seven furrow spines ( Fig. 8E ).

Comments. This specimen represents a significant range extension for this species, which has previously only been documented from the Bay of Plenty in New Zealand (no depth noted). This first Indian Ocean occurrence differs in that the abactinal plates are more convex, abactinal spines are more conical (vs. more cylindrical in the New Zealand specimen), a greater number of superomarginals abut over the arm radius beginning at the base of each arm (rather than midway along the arm distance), each superomarginal plate shows a strong convex curvature with a more pronounced smooth, bare surface, and there are only one or two spines present on each superomarginal plate, rather than the two to three spines present in the New Zealand holotype (R= 8.3 cm). Pedicellariae were also not observed on this specimen whereas small spatulate pedicellariae were observed on the New Zealand holotype .

This species bears immediate similarities with the South African Calliaster acanthodes H.L. Clark in that the abactinal surface displays a similar abactinal surface covered by prominent, conical spines. However, this species possesses abactinal plates extending to the arm tip with spineless abactinal arm plates. Marginal plates in Calliaster acanthodes are more quadrate in shape (i.e. closer length and width) and are directed laterally rather than producing a prominent abactinal facing. Actinal granulation in Calliaster acanthodes is well-developed, whereas the actinal surface in C. thompsonae is devoid of all surficial granulation, including granules.

Occurrence. Bay of Plenty, New Zealand to Northeast coast of Somalia, 75–175 m.

Description. Body stout, stellate (R/r=2.6) in outline, arms elongate, disk arched, interradial arcs broadly curved.

Abactinal plates abutted, plate surfaces flat to weakly convex. Individual plates round to polygonal in outline, mostly homogenous in size, shape. Minority of plates small (about 25% of the size of a majority sized plate). Abactinal plates restricted to disk only, none beyond basal arm region. Carinal plates ranging from round (proximally) to oval (distally) in shape. Fasciolar grooves present, developed channels present around plates, six papulae present around each plate, present only over radial regions. Abactinal plates each plate with a single, prominent, sharp, conical spine ( Figs. 8A, B ) with only a minority of plates (two to five per interradius) lacking spines. These spines, ranging in length from 1.0 to 3.0 mm project well above the abactinal surface ( Fig. 8B ). Those plates lacking spines located around the periphery of the abactinal plate field, adjacent to superomarginal contact. Primary circlet plates along each radial series each with enlarged sharp, conical spine approximately twice as thick and about 25% longer than other abactinal spines. Granules, eight to 50, mostly 10–40, bead-like in shape, widely spaced around periphery of each plate ( Fig. 8B ). Madreporite convex, with well-developed sulci, flanked by three abactinal plates. No pedicellariae.

Superomarginal and inferomarginal plates eighteen per interradius (arm tip to arm tip) ( Fig. 8A ), these series are slightly offset, forming zig-zag contact between them. Length of each plate with approximately 20–25 beadlike, widely spaced granules, approximately 30–50 along each width. Superomarginals six, very wide (4x the length), forming prominent distinct abactinal facing border in each interradius, arms with six plates abutted over midline on arm ( Fig. 8A, C ). Abutted superomarginals show mostly 1:1 correspondence, but one arm with slightly offset plates showing zig-zag contact along the arm mid-radius. Superomarginal surface strongly convex with smooth surface bearing no surficial accessories (no granules, etc.). Interradial superomarginals with two prominent, conical spines directed away from one another ( Fig. 8B, C ), with one directed laterally and another directed abactinally. Remainder of superomarginal plates each with a single prominent conical spine, in lateral directed series. The holotype with distalmost six plates missing spines showing only remaining convex spine base. One arm damaged with strongly convex, truncated superomarginal plates. Distalmost superomarginals becoming more quadrate with more acutely convex surface. Inferomarginal plates mostly with a single lateral series of conical, pointed spines. One to three inferomarginal plates exceptionally with two spines. No other surficial accessories. Surface smooth and bare. Inferomarginals present interradially wide (about 4x the length) becoming more elongate along arms (about 3– 4x the width). Terminal plate rhombic in shape but with broadly rounded edges, two short blunt spines. No pedicellariae on marginal surfaces.

Actinal surface, plates restricted to disk, composed of two full series in chevron-like series ( Fig. 8D ) with approximately three to five irregularly shaped plates becoming more jumbled in series distally. Individual plate surface flat to weakly convex, quadrate to irregularly polygonal in outline. Most plates with a large, prominent cylindrical blunt spine, one per plate, each spine approximately 1–2.0 mm in length ( Fig. 8D ). Actinal plate surface smooth and bare, no surficial accessories (no granules, pedicellariae, etc.). Peripheral granules, five to 20, bead-like in shape, widely spaced around actinal plate periphery. Actinal plates adjacent to inferomarginals smallest and most irregular in shape, with a minority lacking spines.

Furrow spines six or seven in weakly convex to straight fan ( Fig. 8E ). Two enlarged subambulacral spines in transverse series, comparable in size with other actinal spines, approximately 5x the width and thickness of a furrow spine. Adambulacral plate surface otherwise bare with no surficial accessories ( Fig. 8E ). Adambulacral plate surface flattened to weakly convex. Oral plates with six to eight furrow spines, one enlarged blunt spine per plate projecting into mouth, two prominent subambulacral oral spines identical to those on adambulacral plates. Two paired series of six to eight angular granules flanking each side of an oral sulcus where halves of the oral plate are in contact.

Material Examined. USNM 1510318 , off NE coast of Somalia and south of Socotra Island 11°24’N 51°35’E. 75–175m, Coll. R / V Coll. R / V Anton Bruun cruise 9, st. 463. 1 wet spec. R=4.2 r=1.6

Figures

FIGURE 8. Calliaster thompsonae USNM 1510318. R=4.2, r=1.6 cm. A. Abactinal surface. Scale bar=1.0 cm. B. Closeup of abactinal surface and superomarginal plates. Scale bar=0.2 cm. C. Arm and marginal plates. Scale bar=0.5 cm. D. Actinal surface. Scale bar=1.0 cm. E. Adambulacral and furrow spines. Scale bar=0.1 cm.