Ophiomusium lütkeni Lyman, 1878

Baker, Alan N., 2016, An illustrated catalogue of type specimens of the bathyal brittlestar genera Ophiomusium Lyman and Ophiosphalma H. L. Clark (Echinodermata: Ophiuroidea), Zootaxa 4097 (1), pp. 1-40 : 14

Ophiomusium lütkeni Lyman, 1878 .

Figures 19 a, b

Ophiomusium lütkeni Lyman, 1878 ; H. L. Clark, 1939. Ophiomusium impurum Koehler 1904 ; Stöhr, 2011.

Holotype BMNH 82.12.23.398 Challenger station 192, Arafura Sea, 236 m. Syntype, MCZ 474 Challenger station 192, near Kei Ids, 235m.

There are also many specimens of this species collected by the John Murray Expedition at station 106: BMNH 1949.1.10.134-153, 183– 194 m, and 9 specimens in the USNM (E0037252): Off Zanzibar, 240 m; 3 specimens, possible syntypes, NMRH, V.Ech. O. 2038, Siboga Station 65a, Flores Sea, Indonesia, 400 m; 3 specimens, possible syntypes, NMRH V.Ech. O. 2039, Siboga Station 253, N of Pulau Yamdena, Indonesia, 300 m. Dr Marc Eleaume, Paris Museum has recently informed me that a syntype of O. impurum in in their collection: NMNH 10316, ex- Siboga .

Main Features: The type is 14 mm d.d. The lower edge of the interradial plates protrude further than other adjoining plates, and they have a roughened margin. The lateral arm plates have a very sharply angled spine-bearing central ridge, which give the arms a serrated appearance. No genital papillae. Two pairs of exposed tentacle pores.

The John Murray Expedition material (8–10 mm d.d.) has the same interradial plates as the type specimen but the plates bordering the oral shield are different, in that there are two plates obliquely overlapping, lying distal to the oral shield. On the dorsal surface of the arms the lateral plates project above the midline, leaving the dorsal arm plates in a depression. The radial shields are uniformly oval, unlike the angular shields in Lyman’s figure.

The Flores Sea specimens are 4, 7 & 8 mm d.d. They have large interradial plates with hollowed, outwardly oblique marginal surfaces. Radial shields diamond-shaped, disc centre is sunken, with a few symmetrically arranged plates. Distal ends of radial shields slightly swollen. Arms distinctly moniliform. Spine ridges quite angular. Two pairs of exposed tentacle pores. First two ventral arm plates large, remainder small, wider than long but present to the end of the arm.

The Pulau Yamdena specimens have the large interradial plates and the saw-tooth like arms which characterise this species. There is also one from this station which has a bifurcate arm. The largest specimen is 10 mm d.d.

Figures

FIGURE 19. Ophiomusium luetkeni BMNH 82.12.23.398: a, b, dorsal and ventral disc sectors.