Ophiacantha cosmica Lyman, 1878: 146

Stöhr, Sabine & O’Hara, Timothy D., 2021, Deep-sea Ophiuroidea (Echinodermata) from the Danish Galathea II Expedition 1950 - 52, with taxonomic revisions, Zootaxa 4963 (3), pp. 505-529 : 520-522

Ophiacantha cosmica Lyman, 1878: 146 , pl. 10 figs 251–254, 262–265, 269, 270.

Figure 4E–G

Material examined

TASMAN SEA • 1 specimen; 39°45’S; 138°42’E; 4670 m; 18 Dec. 1951; Galathea II stn.574; NHMD-867439 • 1 specimen; 45°47’S, 164°39’E; 4390 m; 13 Jan. 1952; Galathea II stn. 599; NHMD-867198 • 20 specimens; 45°51’S, 164°32’E; 4360–4400 m; 14 Jan. 1951; Galathea II stn. 601; Globigerous ooze; NHMD-867169.

KERMADEC TRENCH • 10 specimens; 36°07’S, 178°32’E; 5230–5340 m; 23 Feb. 1952; Galathea II stn. 661; pumice in abundance; NHMD-305713 • 60 specimens; 36°31’S, 178°38’E; 4410 m; 24 Apr. 1952; Galathea II stn. 663; brown sandy clay with pumice; NHMD-868292, NHMD-867168 • 27 specimens; 36°34’S, 178°57’E; 4540 m; 24 Feb. 1952; Galathea II stn. 664; brown sandy clay with pumice; NHMD-867468.

Comparative material

EAST PACIFIC OCEAN• 1 specimen labelled as O. cosmica ; 34°14’00’’N, 096°28’00’’W; 2232 fathoms [4085 m]; 08 Apr. 1891; Albatross stn. 3414; NHMD (uncatalogued).

Remarks

The original material of O. cosmica was slightly larger than O. pacifica , with up to 18 mm disc diameter ( Lyman 1878). It had a large, blunt ventral tooth, a widened distalmost papilla and three slender pointed lateral papillae along each jaw, and additional papillae on the jaws. The number of arm spines was also higher (up to eight) and the shape of the oral shield differed. In other respects, the species are similar (see remarks with O. pacifica ). In the Galathea material, specimens from the East Pacific Ocean were originally identified as O. cosmica , based on the presence of additional papillae on the jaws. Considering molecular data ( Christodoulou et al. 2019), these were re-assigned to O. pacifica . Likewise, specimens without additional papillae on the jaws from the Tasman Sea and Kermadec Trench were at first identified as O. pacifica , but later re-assigned to O. cosmica . The number of oral papillae is considered a variable character without taxonomic information and the species complex can at present not be differentiated morphologically (see remarks with O. pacifica ).

The original material of O. cosmica was collected at geographically far apart locations ( Antarctica, Papua New Guinea, Brazil) at a wide depth range (652– 3,931 m), but the holotype and three paratypes (BMNH 1882.12.23.34) originated from station 157 in the Southern Ocean, at 1950 fathoms, (about 3,566 m). We consider O. cosmica and its allies to belong to the lower bathyal to abyssal fauna, restricted to depths below 3,000 m. Specimens from tropical locations and shallower depths, included in Lyman’s (1878) account, most likely belong to other species. Recent reports of O. cosmica from Brazil ( Borges et al. 2002) are based on a misidentification of Ophiacantha pentacrinus Lütken, 1869 . Tommasi (1970) gave the depth distribution of O. cosmica as 40– 4,273 m, which seems highly unlikely, since abyssal species are not known to occur at shallow depths. Tommasi et al. (1988) reported O. cosmica from 400–480 m depth in the Southwest Atlantic, which suggests that the specimens were misidentified. A record of O. cosmica from off Martha’s Vineyard ( Clark 1939) may represent the Atlantic Ophiacantha aculeata Verrill, 1885 , because Clark (1939) had synonymised both species, a decision that was not followed by later authors ( Paterson 1985). According to Paterson (1985), O. aculeata is smaller (to 13 mm dd) than O. cosmica and has a depressed oral shield and a wider distal oral papilla than O. cosmica . Consequently, the occurrence of O. cosmica in the North/Central Atlantic is doubtful, as no reliable records are known.

A specimen labelled as O. cosmica , from the Albatross expedition, mentioned by Lütken & Mortensen (1899), has a disc diameter of 13.9 mm ( Fig. 4C, D ) and agrees with O. pacifica in most respects, but there are additional lateral oral papillae (also noted by Lütken & Mortensen (1899)), crowding in a second row along the jaw edges, six or seven papillae in total, the distalmost not widened ( Fig. 4D ). The ventralmost tooth is as large as in O. pacifica on two jaws but on three jaws, there is a slender tooth or tooth papilla, ventral to the wide teeth. This specimen should be assigned to O. pacifica based on its geographic origin (see remarks with O. pacifica ).

Figures

FIGURE 4. A, B, Ophiacantha pacifica, largest syntype (11.6 mm dd), ZMUC OPH-000399. A, dorsal aspect, B, ventral aspect. C, D, Ophiacantha pacifica (originally identified as O. cosmica by Lütken & Mortensen (1899)), Albatross Exp. stn. 3414, NHMD (unregistered), C, dorsal aspect, D, ventral aspect. E, F, Ophiacantha cosmica, Galathea II stn. 601, NHMD-867169. E, small specimen (12.4 mm dd) with few oral papillae, F, large specimen (22.3 mm dd) with many oral papillae. G, Ophiacantha cosmica, Galathea II stn. 599, NHMD-867198, ventral aspect, H, Ophiacantha sociabilis, Galathea II stn. 281, NHMD-867267 or NHMD-86721, ventral aspect. OPa, oral papillae sensu lato, OS, oral shield, RS, radial shield, T, tooth. Scale bars = 1 mm.