Ophiothrix (Placophiothrix) albostriata H.L. Clark, 1928

O’Hara, Timothy D., 2014, A new species of Sigsbeia and additional records of ophiuroids from the Great Australian Bight, Memoirs of Museum Victoria 72, pp. 131-140 : 136-137

Ophiothrix (Placophiothrix) albostriata H.L. Clark, 1928

Fig. 3

Ophiothrix albostriata Clark, H.L., 1928: 429-430 , fig. 127.

Placophiothrix albostriata .--Clark, H.L., 1946: 227.

Ophiothrix (Placophiothrix) albostriata .--Clark, A.M., 1967: 648.-- Baker & Devaney, 1981: 167, fig. 49-54.-- Rowe & Gates, 1995:427.

Material examined. -- Great Australian Bight , holotype: 1 ( SAM K215 ). -- Great Australian Bight, 75 nm SSW of Pearson Is, 35° 8'S, 133° 47'E, 920-1040 m, 1989: 2 ( SAM K2748 ) .

Distribution. Great Australian Bight,? 200-1040 m.

Remarks. This is the first record of this species since the 10 mm d.d. holotype was described by H.L. Clark in 1928. Baker & Devaney (1981) figured the dorsal disc and arms of the holotype. Key diagnostic characters include the large (2/5 d.d.) naked radial shields; the tall (3-4x longer than wide) cylindrical disc stumps with a crown of small thorns; the wide (2x as wide as long) dorsal arm plates, with a centrally produced distal margin, and two longitudinal lines (after the 20th segment); up to 9 arm spines, the longest (2-3rd from the top) measuring 2x the width of the dorsal arm plate, slightly expanded at the tip, with thorns largely restricted to the apical half of the spine; oral shield diamond-shaped, twice as wide as long; ventral arm plates rectangular, 1.5x as wide as long, with a straight distal edge, and a minute tentacle scale that becomes hook-shaped distally with 2-3 accessory points.

The two new specimens are considerably larger than the type, 16 and 17 mm d.d., but share many of the features. Differences include the elongated thorns on the disc spines, which can measure ½ the height of the spine, the presence of a row of minute spines along the abradial edge of the radial shield, and the distal edge of the dorsal arm plates with is convex rather than medially produced. The largest specimen ( Fig. 3a) has three longitudinal broken lines along the arm, occasionally darkened into discrete spots, which can also occur at the distal end of the radial shields.

These specimens were collected from 920-1040 m, which is exceptionally deep for an ophiotrichid. The collection details on the type specimen only list the locality (Great Australian Bight) and not the depth, latitude/longitude or date. Like many other specimens described by H.L. Clark in 1928, they were presumably collected by the malacologist Joseph Verco, who is known to have participated in an expedition by the Australian fishery research vessel ‘Endeavour’ to the Great Australian Bight in March 1909 ( Verco 1935). They trawled predominately along the “one hundred fathom line” in approximately 125-220 m of water in an area 30-120 nautical miles (55-222 km) west of Eucla. Possibly this species is restricted to the upper continental slope (200-1040 m).