Evoplosoma pharos, Mah, 2023

Mah, Christopher L., 2023, New Goniasteridae and in situ observations significant to deep-sea coral predation, Memoirs of Museum Victoria 83, pp. 1-35 : 21

Evoplosoma pharos n. sp.

urn:lsid:zoobank.org:act:4D9D9E7C-E98B-45D0-8493-

FCCBDA6617C6

Figure 9a–f

Etymology. The species epithet, pharos , is Greek for “mantle” or “shroud”, alluding to the fleshy granule-invested dermis.

Diagnosis. Body stellate (R/r=3.9) with arms elongate and tips pointed. Disk pentagonal with arms distinct, interradial arcs weakly angular to straight. Abactinal and actinal surfaces covered by granule-invested dermis. Granules round to irregularly polygonal in shape. Surface with blunt tubercles and weakly pointed conical spines. Marginal plates 50–52, individual plate surface smooth and bare with no granular cover. Single central spine or arched mount present on most plates. Furrow spines mostly 9–10, each round and blunt, quadrate in cross-section. Subambulacral pedicellariae and spine present, but specimen damage did not permit characterisation.

Comments. This species shows distinct similarities with the North Pacific Evoplosoma claguei Mah et al. 2010 , including the granule-invested fleshy dermis, the presence of short conical spines on the abactinal surface, granules absent from the marginal plate surface, and one or two blunt single spines on each marginal plate. Many of the superomarginal and inferomarginal plates along the arm have only a prominent arched projection where the spine would be on other plates, suggesting that these were damaged and are recovering.

This species is distinguished by the greater number of furrow spines, nine or ten versus 4–6 in E. claguei , the single spines present on the interradial marginal plates versus the multiple spines in E. claguei , and the shape of the interradial marginal plate series is also different (wide in E. pharos n. sp. but more square in E. claguei ).

Occurrence . Off New South Wales, Australia. 2595– 2474 m .

Description. Body stellate (R/r=3.93), arms narrow, elongate with tips pointed. Interradial arcs weakly angular to straight.

Abactinal surface arched, forming sunken region adjacent to contact with superomarginals (disk membrane may have deflated). Abactinal plates concealed by a granule-invested dermis. Abactinal plates extend from disk along arms where plate number decreases to 3–5 rows, then to a single row extending to terminus. Surface covered by small, round to irregularly shaped granules, evenly but widely distributed. Moderately large, hemispherical tubercles to short conical spines present uniformly on abactinal surface (specimen lacking many of these, presumably lost during collection). Arm plates with larger, more distinct, conical spines, one per plate. Madreporite convex, polygonal, flanked by approximately six plates. Sulci well developed. No pedicellariae.

Marginal plates 50–54, 52 in each interradius (arm tip to arm tip), with plates interradially and arm plates displaying lateral facing with distalmost plates encroaching upon abactinal surface adjacent to terminus, number of plates decreasing along arm. Marginal plates wide with rounded lateral edge, overall shape quadrate. Marginal plate surface tumid, becoming more so distally. Both superomarginal and inferomarginal plates with a single, prominent spine with a blunt tip. Distally, adjacent to the terminus, spines absent from superomarginal and inferomarginal plate surface. Most marginal plate surfaces lacking accessories (granules, spinelets, etc.). Interradial superomarginal and inferomarginal plates with 3–30 small granules and 1–3 tubercles, variably present on different plates. Marginal plates granulate, evenly spaced, approximately 40, 10 per side, but with some directly interradial plates granules are numerous at contact between superomarginal and inferomarginal plates. No pedicellariae.

Actinal plates in approximately three full series; none extends along arm. Individual plates quadrate to polygonal, with same granule-invested dermis as on abactinal surface. Granules round to polygonal, covering plates completely, such that boundaries are invisible. Tubercles or spines present at approximately one per plate; spines present suggest short, pointed spines, but damage prevents clear assessment. Alveolar pits present, indicating pedicellariae, but damage has left no pedicellariae to characterise.

Furrow spines mostly 9–10, some with as few as six. Each spine with round, blunt tip, quadrate in cross-section. Large alveolar pit suggests the presence of a pedicellaria adjacent to the furrow spines, but these were absent. Broken spine base suggests a prominent subambulacral spine was also present distally on the subambulacral plate. Remainder of subambulacral plate covered by round granules, approximately two irregular rows, each with 4–7 granules. Oral plates with 11–12 furrow spines, with a single prominent spine from each plate projecting into mouth (two per interradius); blunt, flattened, quadrate in cross-section. Oral plate surface covered with 8–10 irregular, angular granules on either edge of the diastema present between the oral plates.

Material examined. Holotype. NMV F241878 , New South Wales, Hunter CMR 32.575° S, 153.162° E, 2595– 2474 m. Coll. T. O’Hara et al. RV Investigator , IN 2017 V03 abyss, 3 June 2017. 1 wet spec, R =11.8, r=3.0.