Ophiolebes paulensis O'Hara & Thuy 2022, sp. nov.

Ophiolebes paulensis sp. nov.

Fig. 9A–C, 10A–P

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Type material. MD50 CP7, north-east of Île Amsterdam, 37° 47.2´S, 77° 38.98´E, 1680– 940m, Beam trawl, 9/7/1986, MNHN IE.2009.1566 (holotype), MNHN IE.2009.1567 (5 paratypes).

Other material examined. MD 50 DC91, MNHN IE.2009.1568 (2).

Comparative Material. Ophiolebes comatulina McKnight, 2003: NZOI / E728, 37° 37.5´S, 177° 12.198´E, 688– 432 m, 25/3/1967, holotype, NIWA 3343 (1). EBISCO/DW2603, Plateau des Chesterfield, 19° 36´S, 158° 43.0005´E, 568–570 m, 18/10/2005, MNHN IE. 2013.6311 (1). EBISCO/DW2613, Plateau des Chesterfield, 19° 37´S, 158° 41.9998´E, 519–522 m, 19/10/2005, MNHN IE. 2013.6287 (2). KAH9907/37, Ritchie Hill Seamount, 39° 29.44´S, 178° 25.05´E to 39° 28.51´S, 178° 25.48´E, 1000– 980 m, 3/6/1999, NIWA 41434 (1).

Holotype description. Disc is 5.5 mm dd, the longest attached arm piece is ~ 10 mm long; disc is tumid radially and sunken interradially, covered in rounded non-imbricating scales, embedded in thin skin, ~ 0.5 mm dia, minutely perforated, fully contiguous and more polygonal over the radial shields, slightly separated in the centre of the disc (Fig. 9A). Scales support one, rarely 2, disc spines, tapered conical to cylindrical, thorny on blunt tip, 3 times as high as wide, ~ 0.3 mm high in centre, smaller near margin, base smooth, upper half with more sculptured stereom and some small thorns. Radial shields are evidently bar-like but covered by skin and scales. Ventral disc (Fig. 9B) surfaces are covered in similar scales, 4–5 rows from oral shield to margin, marginal scales with short conical stumps, 2 times as long as wide, but extend only half the way to the oral shield. Genital slits extend from oral shield for 2.5 arm segments, stopping short of the margin. Genital plates visible externally, adradial plates with a short base and broadly curved, abradial ones abut it closely, extending for half the length of the slit.

Jaws are as long as wide, supporting a tapered ventralmost tooth and three spiniform oral papillae, all arising from the oral plate, the proximally pointed inner one representing the infradental papilla, the obliquely pointed middle one the lateral oral papilla and the distal one the adoral shield spine (following Hendler 2018, fig. 16). All papillae are pitted with tiny thorns near the tip, hollow. Four are teeth visible from the external ventral surface, similar shape to the ventralmost one. Oral plates are raised near the papillae and sunken slightly behind. Second oral podia arise from a naked patch between the adoral shields and first VAP. Adoral shields are 3 times as wide as long, sausage shaped, with concave inner and convex outer margins, rounded outer ends, fully contiguous interradially, separated radially by the first VAP. Oral shields are pentagonal, with concave proximolateral margins, obtuse proximal angle, slightly tapering distolateral sides and a truncate distal margin, the distal section of the plate is sunken down to the level of the ventral disc, central section tumid in the madreporite.

First 1–2 DAPs are triangular, wide as long, contiguous. Succeeding DAPs are rounded triangular, with convex distal margin, and long tapered proximolateral sides, with a small truncate proximal margin, sometimes contiguous, or with a small skin-covered bare patch or a small supplementary plate between plates, typically 1.5 to 2 times as long as wide. LAPs are roughly quadrangular, contiguous, arm spine ridge raised slightly, contiguous ventrally but not dorsally. VAPs on the first segment are 1.5 times as long as wide, widest proximally, with straight proximolateral edges and a straight to concave proximal edge, concave sides (to accommodate the adoral shields), straight distolateral edges and a truncate to rounded distal margin, just touching the proximal angle of the 2nd VAPs, 2nd VAPs are fanshaped with straight proximolateral edges, an acute proximal angle and a rounded distal edge, widest at the distal 1/3 of the plate. Tube foot openings are very small, rounded, the proximolateral edges of the VAPs are not concave around the pore. Succeeding plates become as wide as long, well separated from their neighbours, widest in the middle of the plate, and notched around the pore, the distal edge can become centrally concave on distal segments.

Arm spines are rounded, tapering to a blunt tip, hollow, with sculptured stereom but generally no thorns, do not meet basally even on basal segments just free of the disc. Three arm spines occur on the first segments, four on second and third, four on the fourth segment, then five on segment five and six, just free of the disc, an occasional segment has six spines in the middle of the arm. Upper arm spines are generally longest, particularly on the 5th and 6th segment, to 1.7 mm, 2nd spines (from dorsal) about half its length, lower three 1/4 as short and more slender. From about the 10th segment, the upper spine reduces in size becoming subequal with the others, and the lower arm spines become shorter and stouter with proximally directed thorns (Fig. 9C). Tentacle scales absent proximally (or rubbed off), a tiny pointed scale on the ventral edge of LAP in the middle of the arm, 1/10 the length of the VAP.

Colour (preserved). light brown, the tube feet and tips of the arm spines (skin covered?) are darker brown.

Paratype variations. Discs vary from 4.0– 5.5 mm dd, longest arm fragment is 12.5 mm on a 5 mm dd specimen. The distal section of the bar-like radial shields are exposed on some radii. Some specimens have long disc stumps (to five times height/dia) with stereom extending into short thorns around the spine stem as well as the tip.

Paratype ossicle description. Proximal LAPs (Fig. 10A–B) are slightly higher than long, of rounded outline, relatively thin, with strongly convex distal edge; ventral edge oblique, straight, slightly protruding; dorsal edge slightly concave as a result of a weak constriction; outer surface with coarsely meshed stereom, devoid of tubercles or a vertical striation; outer proximal edge with a proximalwards-pointed spur, entirely lined by a band of more finely meshed stereom. Spine articulations (Fig. 10C) are freestanding in a continuous vertical row on a strongly raised distal portion of the LAP, ear-shaped, moderately large, composed of proximally merged dorsal and ventral lobes enclosing nearly equal-sized muscle and nerve openings and with a moderately well-developed sigmoidal fold. Inner side of LAPs have a large, prominent, well-defined, slender digit-1-shaped vertebral articular ridge; poorly-defined spur in the dorsal half of the inner distal edge corresponding to the protruding spur on the outer distal edge of the LAPs; tentacle notches are small, oblique, shallow. Very small, inconspicuous perforations occur close to the ventro-distal tip of the vertebral articular structure.

Vertebrae (Fig. 10E–I) have wide triangular dorsal fossae and with relatively large ventral muscle fossae on both distal and proximal faces; distal articulations are relatively large, hour-glass-shaped (streptospondylous) with a very small ventral projection of the middle saddle; hourglass-shaped proximal articulation with a vertical pore in the ventral half; oblique L-shaped lateral articulation structure corresponding to articular structure on the inner side of the LAP; dorso-distal muscle fossae are deeply carved into the lateral side of the vertebra; relatively large dorsal and ventral furrows, with moderately large podial basins.

Oral plates (Fig. L) are split in distal and proximal halves, approximately as high as long, with adradial muscle fossa lining the ventro-distal edge of articulation area. Dental plates (Fig. 10K) are undivided, very narrow, rounded, with single row of small, shallow tooth sockets surrounded by weakly-defined protruding ring. Abradial genital plates (Fig. 10N) shorter than the adradial ones (Fig. 10O), slender, bar-like without ridges or groves and with a straight adradio-distal tip. Radial shields (Fig. 10P) are strongly elongated, bar-like, slightly bent, devoid of outer surface ornamentation. A proximal dorsal arm spine (Fig. 10D), disc spine (Fig. 10M), and ventral arm plate (Fig. 8J) are also figured.

Distribution. SPA (940–1680 m).

Remarks. This species is similar to Ophiolebes comatulina McKnight, 2003 known from NE New Zealand (432–1000 m) and the Chesterfield Bank, New Caledonia (519–570 m) (O’Hara unpublished data). Ophiolebes comatulina differs in having diamond shaped oral shields (tapering to a distal angle) and a stout tentacle scale on proximal segments, 1/4 the length of the VAP.All the O. comatulina specimens to date have been found on crinoids. Although there is now no evidence of crinoid material with the MD50 Ophiolebes paulensis sp. nov. specimens, the type locality (stn CP7) was the only sample from the survey recorded with crinoids (Arnaud 1990). Other Ophiolebes species have disc granules and/or short spines on the disc (see above) rather than tall stumps. The South African species Ophiosemnotes corynephora (H.L. Clark, 1923) has superficially similar disc spines to the new species but differs in having wide exposed radial shields.

Etymology. Named after the Île Saint-Paul.