Evoplosoma claguei, Mah & Nizinski & Lundsten, 2010

Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, Zoological Journal of the Linnean Society 160 (2), pp. 266-301 : 278-279

EVOPLOSOMA CLAGUEI SP. NOV.

FIGURE 7A–F

Occurrence: Known from CoAxial Cone and Rodriguez Seamount and off Islas Tres Marias in the North Pacific. 730–2405.6 m.

Material examined: HOLOTYPE: USNM 1124507 . Rodriguez Seamount 33°57′N, 121°8′W, 1842.8 m, coll. ROV Tiburon, Sta. T-629, A8, 14.x.2003 (1 wet spec. R = 9.9, r = 2.6 cm) . PARATYPES: SIO E2440 , Islas Tres Marias , Mexico. 21°52′N, 106°12′W, 730 m, coll . R. Wisher, 18.v.1959 (1 wet spec. R = 8.3, r = 2.6) .

USNM 1136366 CoAxial Cone Seamount, 46°30′N, -129°35′, 2405.6 m. Coll. ROV Doc Ricketts, Sta. D 77- A3. 30 Aug 2009 (1 wet spec. R = 11.1, r = 2.7 cm).

Etymology: This species is named after Dr David Clague, MBARI geologist and primary investigator of the cruise on which this species was collected.

Description: Disk pentagonal, with wide inter-radial almost straight lateral sides between arms. Arms elongate and triangular in outline, distinctly set off from the disk appearing to be attached at the disk corners. Abactinal surface inflated, swollen in life.

Abactinal plates rounded polygonal to completely round surrounded by 15–28 small blunt angular accessory granules forming plate periphery. Each plate with one prominent accessory that varies in shape from spherical tubercle to short, pointed granule to large conical (bullet-shaped) spine. Smaller specimens (R = 8.3) lack well-developed spines but have several pointed, bullet-shaped tubercles. Largest spines are about 2.0 mm in length and appear consistent in size across the abactinal surface. Plates bearing large spines, especially those on the arms, are typically bare aside from accessory granules, but smaller plates may be completely covered by smaller accessory granules. Pulpy membrane present over surface, obscuring granulation and plate surface near periphery of disk at contact with marginal plates. Madreporite convex, swollen with shallow sulci present on surface. Abactinal surface on arms is sharply distinct from plates on disk ( Fig. 7C ). Abactinal plates larger, approximately six plates across from superomarginal to superomarginal, narrowing to one to two plates at distal end of arm. Each plate with a large, pointed conical spine per plate. Spine-bearing plates are bare except for periphery of 20–30 pointed granules on each plate ( Fig. 7C ). Spaces between abactinal arm plates covered by flattened, quadrate granules. Pulpy membrane present but not as strongly expressed and difficult to ascertain on dry specimens.

Marginal plate series face laterally, 58–60 plates per inter-radius (armtip to armtip) in the larger specimen (R = 9.9) and 50–54 plates in the smaller specimen (R = 8.3). Quadrate with rounded edges, plates wider distally (W> L) becoming more equivocal [L = W] inter-radially. Plates slightly convex, bare except for spines, and one to four tubercular granules present infrequently. Superomarginals slightly offset relative to inferomarginals. One to four large, conical to chiselshaped spines per plate. Spines (three to four) and tubercles (one to five) present with higher numbers inter-radially. Spine number decreasing distally to one to two spines distally. More weakly developed spines on smaller specimen, with one to five bullet-shaped granules/tubercles present on plate surface. Single spines on inferomarginal plates form a distinct linear fringe. Pointed granules, 55–65 total, form periphery on marginal plates with approximately ten per side in contact with other marginal plates, approximately 15–18 per contact with abactinal surface. Terminal plate smooth but with three conical spines, two on distalmost tip, one on abactinal surface.

Actinal plate, chevron-like pattern is irregular with actinal plate series adjacent to adambulacral series very elongate, approximately three to four times the length of those in the centre of the actinal intermediate areas and angular in shape. Periphery of these plates covered by 13–40 quadrate granules, approximately 20 per side. Approximately 24 per inter-radius with 12 per side. Actinal plates restricted to disk, do not extend onto arms. Remaining actinal plates on disk approximately 25 per inter-radius, circular to irregular in shape, and size but becoming smaller adjacent to contact with inferomarginal plate series. Actinal plates with one to four large, conical spines and/or short, tubercular granules one each plate. Accessory number varies with plate size. Actinals plates elongate with up to four spines and/or granules whereas smaller, circular plates with single spine.

Adambulacral plates elongate. Furrow spines four to six. Six proximally and decreasing in number distally. Nine to ten furrow spines on first adambulacral plate. Furrow spines flattened, paddle like to triangular in cross-section many with roughened, worn down ragged tips. Degree of wear varies from spine to spine but seems more pronounced on proximal spines. Subambulacral ornament composed of a single large clam-shell to paddle-shaped pedicellariae proximal on the adambulacral and an extremely thickened, large spine, many with pronounced club-like to almost lobate head with worn tip sometimes with pronounced striations. Ambulacral and subambulacral series flanked by ten to 15 round, hemispherical granules varying in size. Largest adjacent to subambulacrals, becoming smaller and flatter adjacent to actinal inter-radial regions. Oral plates with four thick oral spines (quadrate in cross-section) projecting into mouth (two per plate) and four to five on surface of oral plate at apex of inter-radius. These latter spines are thick and round to quadrate in cross-section. Spines have worn tips with striations. Region between the oral plates and remainder of the actinal intermediate plates is covered by flattened, round granules, densely packed, similar to those adjacent to the subambulacral plates.

Colour in life was orange-reddish.

Figures

Figure 7. Evoplosoma claguei sp. nov. USNM 1124507. Holotype. A, abactinal surface; B, close-up showing abactinal plates, spines, and marginal series; C, abactinal plates on arm surface; D, actinal surface; E, close-up of furrow spines and adambulacral armature; F, In situ observation of Evoplosoma (cf. E. claguei) feeding on Keratoisis from Rodriguez seamount (dive 662-02, at 1842 m). Scale bars: A, D = 5mm; B, C, E = 3 mm; F = 5 cm.