Ophiomusium scalare Lyman, 1878

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 : 137-138

Ophiomusium scalare Lyman, 1878

Fig. 4

Ophiomusium scalare Lyman, 1878a: 117-118 , pl. 1(1-3).-- Lyman, 1882:95-96, pl.1(4-6).-- Koehler,1897:308-312,pl.6(24-25).-- Koehler, 1899: 26-28, pl. 2(12-13), 3(21).-- Koehler, 1904: 65.--Clark, H.L., 1915a: 334.-- Matsumoto, 1917: 285-268, fig. 77.-- Koehler, 1922: 417, pl. 89(7), 90(1-2).-- Koehler, 1930: 242-243.-- McKnight, 1975: 64-65.-- Irimura, 1981: 40-41.-- Guille, 1981: 454, pl. 9(56-57).-- Vadon & Guille, 1984: 584.-- Rowe, 1989: 287.-- Imaoka et al., 1990: 93, fig. 51.-- McKnight, 1993: 176, 189.--Liao & Clark, A.M. 1995: 296-297, fig. 167.-- Rowe & Gates, 1995: 435.-- Stöhr, 2011: 45-46, fig. 21g-I.

Ophiomusium aporum Clark, H.L., 1928: 447-449 , fig. 134.--Clark, H.L., 1946: 275 [new synonymy].

Non Ophiomusium aporum .-- Madsen, 1967: 143, fig. 8 [= Ophiomusium incertum Koehler R, 1930 ; according to Baker, 1979].

Material examined. -- ‘ Spencer and St Vincent Gulfs’, holotype of O. aporum : 1 ( SAM K255 ) . -- 100 nm SSE of Cape du Couedic , 900- 1000 m, 1988: 1 ( SAM K3990 ) . -- SS03/2008: stn 47, Great Australian Bight , 35° 12.564'S, 134° 27.012'E, 456 m, 2008 to 2008: 1 ( MV F159801 ) . -- SS03/2008: stn 69, 35° 8.436'S, 134° 16.482'E, 450 m, 2008 to 2008: 15 ( MV F159741 ) . -- SS03/2008: stn 126, 35° 13.77'S, 134° 30.798'E to 35° 14.268'S, 134° 30.78'E, 300-400 m, 2008 to 2008: 4 ( MV F159752 ) . -- SLOPE: stn 203, Off Murray River mouth Encounter Bay, 37° 1.42'S, 137° 44.19'E to 37° 1.13'S, 137° 44.18'E, 403 m, 1994 to 1994: 18 ( MV F89438 ) . -- FR0694: stn 22, 58 nm SW Coffin Bay , 35° 27'S, 134° 48.6'E, 300-400 m, 1994: 10 ( SAM K2770 ) . -- SS10/2005: stn 80, Jurien Bay , 29° 50.514'S, 114° 21.72'E to 29° 51.012'S, 114° 22.02'E, 408-427 m, 2005 to 2005: 7 ( MV F112020 ) . -- SS10/2005: stn 34, Bald Island , 35° 12.81'S, 118° 39.06'E to 35° 12.24'S, 118° 40.14'E, 431- 408 m, 2005 to 2005: 300 ( MV F111164 ) .

Distribution. India, Indonesia, western and south-western Australia, Philippines, Japan, SW Pacific from Papua New Guinea to the northern Louisville Ridge. Depth range 124- 1100 m

Remarks. H.L. Clark (1928) described two specimens of Ophiomusium from South Australia as a new species O. aporum . However, in 1946 he subsequently synonymised his species with O. incertum Koehler, 1930 , the existence of which he had been unaware in 1928. Baker (1979) re-examined both specimens and referred the holotype ( SAM K481) to O. australis H.L. Clark, 1928 , on the basis that tentacle pores are present on the first two arm segments, but leaving the smaller 3.3 mm d.d. paratype ( MCZ 4712) as O. incertum .

However, after examination of hundreds of Ophiomusium specimens from southern Australia, we consider that there are three species characterised by having two-tumid plates along each disc margin. These are 1) O. australe with smooth disc plates, two arm spines (see O’Hara 1990), two ventral arm plates and pore pairs (see Baker & Devaney 1981 fig. 25-28), 2) O. incertum with granulated disc plates, 3-5 arm spines, no obvious pore pairs (except in small juveniles, see O’Hara 1990), and no ventral arm plates (see Madsen 1967 fig. 8), and 3) O. scalare with disc covered in wrinkled skin, 3 arm spines, and two ventral arm plates and pore pairs.

We judge that the holotype of Ophiomusium aporum is closer to O. scalare than O. incertum , as it has wrinkled skin on the disc, two (although frequently indistinct) pore pairs, and 3 arm spines. However, O. scalare is morphologically variable (particularly the appearance of the dorsal disc) across its large range and the form found off SW Australia could easily be a separate cryptic species for which the name O. aporum would be available. Ophiomusium scalare is known from the Andaman Islands to Tonga, and Japan to the Taupo Seamount in the Tasman Sea. It usually occurs in 100-1500 m. A very similar species, O. ultima Hertz, 1927 has been recorded off eastern Africa. We have not had the opportunity to examine the smaller paratype of O. aporum in the MCZ which has been described as having no tentacle pores and a granulated disc. Our other records of O. incertum are restricted to Tasmania and eastern Bass Strait.