Ophiorupta discrepans (Koehler, 1922) Martynov, 2010

Martynov, Alexander, 2010, Reassessment of the classification of the Ophiuroidea (Echinodermata), based on morphological characters. I. General character evaluation and delineation of the families Ophiomyxidae and Ophiacanthidae 2697, Zootaxa 2697, pp. 1-154 : 94-95

Ophiorupta discrepans (Koehler, 1922) comb. nov.

Figures 13A–B; 18E–H; 63; 64

Ophiomedea discrepans Koehler, 1922a: 95–98 , plate 26, figs 1–4 Material. Holotype USNM 41196 , dried, R/V “Albatros”, sta. 5359, depth 4160 m; ZMMU D-806, R/V “Vityaz”, sta. 5028, 7° 43,3' N 120° 20,1' E, depth 4110–4111 m.

Description of the specimen from sta. 5028. The disk is damaged and ca. 7 mm in dd, not indented interradially. The disk plates are almost entirely concealed by numerous small granules. Radial shields are small and concealed under disc scales. The interradii are slightly swollen, ventrally covered with numerous small granules. Areas adjacent to the genital slits are almost entirely devoid of granules. Genital slits are long, proximally bordered by a well-defined abradial genital plate. Each jaw bears five to seven irregularly placed narrow spiniform apical papillae. The latter are clearly distinguished at least from the dorsally placed teeth, which are elongated and more massive. The adjacent 3–4 lateral oral papillae are similar to the ventralmost teeth (apical papillae) and together form a row of similar spiniform papillae. Between the lateral and adoral papillae there is a more or less clear gap, which is however in some interradii almost indistinghuishable. The adoral papillae are 2–3 times larger than the 3–4 lateral papillae. Two of the adoral shield papillae are properly placed on the adoral shield whereas 1–2, similar in shape to the adoral papillae, are placed on the jaw. The ventralmost teeth are numerous (ca. 12 in number) and distributed in a cone-shape tapering dorsalwards; the dorsal teeth instead are more massive, elongated and placed one by one. The oral shield is wide, arrow-shaped with small narrow distal lobe and large triangular proximal part, about as wide as long, completely separated from the first lateral arm plate by the adoral shields. The madreporic oral shield is slightly but evenly swollen, the distal lobe is not clearly separated from the rest of the shield and its general shape is a regular lozenge. The adoral shield is narrow wing-shaped laterally, widely adjoining the arm, slightly narrowing towards the midline of the jaws, thus retaining only a narrow bar between jaws and oral shield.

The arm length is about two times the disk diameter. The dorsal arm plates are well developed but thin, triangular, relatively small, rather narrow even on the proximal segments, gradually narrowing further toward the distal part of the arm, slightly separated on few proximal segments and widely (up to 2/3 of the dorsal arm plate length) distally. The distal edge of the dorsal arm plate is slightly convex throughout the length of the arm. About two proximal arm segments lack the normal dorsal arm plates and bear instead few small rounded scales, which are dorsal disk scales including granulation. Arms have more or less conspicuous nodes and lateral arm plates have a low lateral ridge, on which the large spine articulations are placed. There are two spines on the first segment, three on the other segments under the disk, three to four moderately erect spines on the free proximal and middle segments, and three distally. The dorsalmost spines on the proximal segments are the longest, up to length of two segments. Spines are flattened, pointed apically.

The first ventral arm plate is irregularly trapezoid. Suceeding ventral arm plates have a characteristic pole-axe shape throughout the entire arm length. The proximal edge of the ventral arm plate is slightly concave or straight on the first 2–4 proximal segments, whereas the distal edge is convex. On distal segments the proximal edge of the ventral arm plate is triangular. Ventral plates are contiguous on the first 4–5 segments and separated on further segments for up to half of their length. The tentacle pores are larger and more conspicuous proximally than towards the distal end of the arm. Two first proximal segments bear three large elongated, flattened, slightly apically pointed tentacle scales, two on the lateral arm plates and one opposite to the others on the ventral plate. Further segments lack the third tentacle scale and bear only two scales on the lateral plates. The tentacle scales are shorter the arm spines but conspicuous and capable of covering the whole tentacle pore. Distally there are also two scales, but considerably reduced in size.

Internal and microstructural characters. The study was limited, because only a single specimen was available. Jaws are slightly elongated. Dental plate is without folds, with few small rounded sockets in the ventral part and few elongated ones dorsally ( Fig. 13A). Arm spine articulations are well developed and represent the double-opening type, but the second opening is not always distinct ( Figs 63F–G, H; 64H–P). The muscle opening is placed within the somewhat transversally compressed and elongated ridge, with a distinct distal lobe. The sigmoidal fold is absent. The nerve opening is placed laterally and distally from the muscle opening, but indistinct. Vertebrae are rather long, not keeled and with well developed zygospondylous articulation ( Figs 18E, H). Vertebral dorsal median groove is indistinct, but broad ( Fig. 18E). Podial basins are large ( Fig. 18F).