Ophiacantha quadrispina H. L. Clark 1917

Ophiacantha quadrispina H.L. Clark, 1917

Fig. 10G‒L

Ophiacantha quadrispina H.L. Clark, 1917: 432‒433, pl. 1, figs. 3‒4, pl. 2, fig. 3.

Material examined. Three individuals at three stations. TALUD XIV, Sta. 7, 1 ind. (ICML-EMU-11674); Sta. 15, 1 ind. (ICML-EMU-11216). TALUD XV, Sta. 23, 1 ind. (ICML-EMU-12997).

Comparative material. Syntypes, 4 ind.: MCZ OPH-4478, USNM E686, USNM E687, USNM E688 (Supplementary file 2).

Description (ICML-EMU-12997). DD = 9.9 mm. Disc pentagonal. Dorsal disc covered by granules and scales. Primary plates not evident. RS oval, small (covering ¼ of disc radius), separated (Fig. 10G). Ventral interradii covered by scales and some elongated granules distally. Genital slits with conspicuous imbricated scales (Fig. 10H). OSh broader than long, diamond-shaped with rounded edges, distally elongated. Madreporite larger than OSh.AdSh longer than broad, slender, distally projecting and surrounding AdSh, meeting in front of Osh or separated. Jaws bearing 6‒7 papillae at each side; AdShSp rounded; LOPa 4‒5, elongated, pointed, some of them placed in two rows; IPa pointed. vT quadrangular, located behind the pair of IPa (Fig. 10I). Arms fragile. First DAP covered by scattered granules; subsequent DAP as long as broad, diamond-shape, meeting. Longitudinal swollen keel along the DAP (Fig. 10J). VAP broader than long, pentagonal with rounded edges, meeting or almost meeting. LAP with four ArSp, large (approximately 2.5 arm segments in length), smooth, flattened, dorsalmost largest, ventralmost shortest. First seven tentacle pores with two TSc; subsequent pores with one lanceolate TSc (Fig. 10K). Color pattern in dorsal disc and arms brown, ventral side beige (Fig. 10G‒L). DAP with longitudinal brown and beige bands (ethanol preservation) (Fig. 10J).

Habitat and distribution. Mexico and the Galapagos Islands, Ecuador; 183‒ 871 m depth, muddy, sandy, and rocky substrates and gorgonians (H.L. Clark 1917; Maluf 1988; see Remarks). The material examined was collected off western Baja California Sur and in the northern Gulf of California; 203‒871 m depth.

Remarks. The genus Ophiacantha is a heterogeneous taxon that contains several groups of species that are difficult to place taxonomically (O’Hara & Stöhr 2006). According to Christodoulou et al. (2019), Ophiacantha quadrispina clusters with Ophiotoma species and some Ophiomitra and Ophiopristis, suggesting that it does not belong to Ophiacanthidae but to the Ophiotomidae. Consequently, a complete revision of the genus is needed to determine the correct generic placement of O. quadrispina. Ophiacantha quadrispina was previously known only in the Gulf of California (Granja-Fernández et al. 2015) and at a maximum depth of 549 m (Maluf 1988). Material examined from off western Baja California Sur (27º8′11″N; 114º32′54″W) represents a new distribution record and an extension of its lower bathymetric limit to 871 m depth.