Ophiacantha eurypoma H. L. Clark 1911

Ophiacantha eurypoma H.L. Clark, 1911 Fig. 9A‒F Ophiacantha eurypoma H.L. Clark, 1911: 223‒224, fig. 103.— Lambert & Boutillier 2011: 41, fig. 27. Ophiophthalmus eurypoma. Kyte 1969b: 106, 108. Material examined. Six individuals at one station. TALUD XVIB, Sta. 22, 6 ind. (ICML-EMU-11184). Comparative material. Syntypes, 3 ind.: MCZ OPH-3201, USNM 25626 (Supplementary file 2). Description (ICML-EMU-11184). DD = 8.3 mm. Disc rounded, slightly indented. Dorsal disc covered by imbricated scales and scattered and short multifid spines. Primary plates not evident. RS slightly broader than long, without multifid spines, meeting but with a k-plate inserted proximally (Fig. 9A). Ventral interradii covered by imbricated scales and spines similar to those on the dorsal side (Fig. 9B). OSh broader than long, diamondshaped with rounded edges. Madreporite swollen and with a rounded depression. AdSh longer than broad, curved, trapezoidal, almost meeting or meeting in front of OSh. Jaws bearing three papillae at each side; AdShSp pointed, larger than rest; LOPa elongated, pointed; IPa elongated, pointed, slender. vT wider than oral papillae, leaf-shaped (Fig. 9C).Arms slender, gradually narrowing distally. First two DAP reduced, covered by multifid spines; subsequent DAP slightly longer than broad, triangular with rounded edges, separated from each other (Fig. 9D). VAP broader than long, heptagonal, separated from each other. LAP with 6‒7 ArSp, large (approximately two arm segments in length), serrated, dorsalmost and ventralmost the shortest, middle the largest. One lanceolate TSc (Fig. 9E). Color pattern beige-whitish (ethanol preservation) (Fig. 9 A‒F). Habitat and distribution. Alaska, USA, and northern Mexico (H.L. Clark 1911; see Remarks); 1,041 ‒2,871 m depth, muddy substrates (H.L. Clark 1911; Maluf 1988). The material examined was collected off western Baja California; 1,480 ‒1,560 m depth. Remarks. Larger specimens of Ophiacantha eurypoma (DD = 15 mm, syntype USNM 25626) present a densely covered dorsal disc with short multifid spines, 7‒8 arm spines, and the adoral shields always meeting in front of the oral shield. The previously reported distribution of O. eurypoma included Alaska and USA (H.L. Clark 1911); it was recorded in western Mexico (Hendrickx 2012a), but as a record pending confirmation (GranjaFernández et al. 2015). During the revision of the TALUD material, the species identification was corroborated for the Mexican Pacific, with western Baja California (30ºN) being the southernmost record in the eastern Pacific. Its distribution across the North Pacific can be explained based on the fact that during past glacial events, a number of temperate-water marine invertebrate species were able to extend their distribution ranges to the Mexican section of the North Pacific (e.g., the hydroid Nemertesia mexicana Ramil & Vervoort, 2007, the sea stars Henricia aspera Fisher, 1906 and Lophaster furcilliger Fisher, 1905, the holothuroids Abyssocucumis abyssorum (Théel, 1886) and Ypsilothuria bitentaculata (Ludwig, 1893), and the ophiuroids S. ponderosa and Ophiura luetkenii (Lyman, 1860); Maluf 1988; Brusca & Hendrickx 2010; Hendrickx et al. 2011; Massin & Hendrickx 2011). The record for Laguna Guerrero Negro (western Baja California Sur), at 5‒12 m depth (Morales-Zárate et al. 2016), is most probably erroneous because O. eurypoma appears to be a deep-water species (Maluf 1988); this doubtful record probably corresponded to a shallow-water species of Ophiotrichidae, which feature a general morphology similar to members of the Ophiacanthidae.Published as part of Granja-Fernández, Rebeca, Hendrickx, Michel E., Rangel-Solís, Pedro Diego & López-Pérez, Andrés, 2023, Deep-sea Ophiuroidea (Echinodermata) collected during the TALUD cruises in western Mexico, pp. 1-71 in Zootaxa 5259 (1) on page 35, DOI: 10.11646/zootaxa.5259.1.1, http://zenodo.org/record/779498