Amphiophiura oligopora (H.L. Clark, 1913)

Fig. 5G‒L

Ophiura oligopora H.L. Clark, 1913: 210‒211, pl. 35, figs. 8‒9.

Material examined. 74 individuals in seven stations. TALUD VIII, Sta. 3, 1 ind. (ICML-EMU-11128-B). TALUD XII, Sta. 23, 2 ind. (ICML-EMU-11129-A); Sta. 28, 67 ind. (ICML-EMU-11139). TALUD XV, Sta. 5C, 1 ind. (ICML-EMU-11131-A); Sta. 24, 1 ind. (ICML-EMU-11131-C). TALUD XVIB, Sta. 23, 1 ind. (ICML-EMU-11132-A); Sta. 28, 1 ind. (ICML-EMU-11132-B).

Comparative material. Ophiura oligopora H.L. Clark, 1913, holotype: USNM 31641. Paratype, 1 ind.: MCZ OPH-3618 (Supplementary file 2).

Description (ICML-EMU-11139). DD = 9.4 mm. Disc pentagonal with a central depression. Dorsal disc covered by irregular oval scales. Primary plates oval, conspicuous, separated from each other. RS longer than broad, triangular, separated by large scales, only meeting distally; one oval plate at disc margin between each pair of RS (Fig. 5G). Ventral interradii covered by few scales, similar size to dorsal scales. Genital slits with minute, pointed genital papillae, projecting dorsally and forming discrete arm combs with small, rounded papillae (Fig. 5H). OSh longer than broad, pentagonal proximally, quadrangular with rounded edges distally. Madreporite not evident. AdSh longer than broad, elongated, slender, meeting in front of OSh. Jaws bearing five papillae at each side; BSc rectangular, very elongated; IPa similar to BSc but smaller; 2IPa quadrangular, elongated; TPa two pointed, apicalmost the largest. vT pointed, more large than oral papillae. Preceding ossicles separated by a diastema; one AdShSp, two 2AdShSp, rounded (Fig. 5I). Arms gradually narrowing distally. First three DAP broader than long, overlapping; subsequent DAP longer than broad, trapezoidal, meeting (Fig. 5J). VAP broader than long, oval, separating and decreasing in size distally (Fig. 5K). LAP with three ArSp, short (approximately 1/5 LAP in length), pointed, dorsalmost the longest, often widened at the tip (Fig. 5J). First tentacle pore with three rounded TSc; subsequent tentacle pores with one and none TSc distally (Fig. 5K). Color pattern beige-whitish (Fig. 5G‒L). RS and large plate between them and arms with dark brown tint (ethanol preservation) (Fig. 5G, J).

Habitat and distribution. Only known in western Mexico; 772‒ 1,532 m depth, sandy and muddy substrates (H.L. Clark 1913; Granja-Fernández et al. 2015; see Remarks). The material examined was collected off western Baja California and Baja California Sur, in the southern Gulf of California, and off Colima; 772‒ 1,532 m depth.

Remarks. Amphiophiura oligopora requires revision since the genus Amphiophiura is characterized by having massive oral shields (Matsumoto 1917), a character absent in A. oligopora. It is therefore reported herein as a doubtful member of this genus. The only previously known material of A. oligopora corresponds to the type material (holotype and one paratype) collected in the southern Gulf of California at 1,152 m depth (H.L. Clark 1913). The finding of new material of this species at six localities during the TALUD cruises is therefore very relevant since it represents the only non-type material available to date. It represents new distribution range limits to the north (31º22′00″N; 117º01′60″W) and to the south (18º33′43″N; 103º57′45″W) as well as a new bathymetric distribution range (772‒ 1,532 m).