Ophiolebes felli, O’Hara & Thuy, 2022

O’Hara, Timothy D. & Thuy, Ben, 2022, Biogeography and taxonomy of Ophiuroidea (Echinodermata) from the Îles Saint- Paul and Amsterdam in the southern Indian Ocean, Zootaxa 5124 (1), pp. 1-49 : 21-24

publication ID	https://doi.org/ 10.11646/zootaxa.5124.1.1
publication LSID	lsid:zoobank.org:pub:C015F8CB-799B-4A92-90AE-02B4C576089E
DOI	https://doi.org/10.5281/zenodo.6404718
persistent identifier	https://treatment.plazi.org/id/C72D87A1-534A-FF87-FEA3-85DCFAEDFC08
treatment provided by	Plazi
scientific name	Ophiolebes felli
status	sp. nov.

Treatment

Ophiolebes felli View in CoL sp. nov.

Fig. 7C–I View FIGURE 7 , 8A–S View FIGURE 8

http://zoobank.org/ urn:lsid:zoobank.org:act:E2AF7C6B-E83C-4F14-8DBD-D11F80E0A183

Type material. MD50 CP7, north-east of Île Amsterdam, 37° 47.2´S, 77° 38.98´E, 1680– 940m, Beam trawl, 9/7/1986 GoogleMaps , MNHN IE.2019.4746 (holotype) , MNHN IE.2009.1569 (9 paratypes) .

Holotype description. Disc is 8.3 mm dd, arms are coiled distally but are at least 25 mm long. Both sides of the disc and the arms are covered in skin that obscures underlying plates. Disc is five lobed, constricted interradially, covered in skin with embedded low conical granules ( Fig. 7D View FIGURE 7 ). The granules are largest on and between the radial shields and in the centre of the disc (0.27–0.3 mm dia), on the dorsal and ventral interradii they are smaller (0.18– 0.25 mm), sparser and separated by skin and small scales. The wide genital slits are contiguous with the first 2 arm segments ( Fig. 7E View FIGURE 7 ). Oral shields are rhomboid, 1.5 times wider than long; adorals are almost of the same size, trapezoid, widest proximally, 2 times as wide as long, meeting broadly interradially, slightly tumid; teeth robust, pentagonal, pointed at tip, 3 conical papillae on the ventral margin of the oral plate, the adoral shield spine is slightly larger.

DAPs are fan-shaped, as wide as long, with a rounded distal margin and acute angle proximally, separate. Some disc granules are present along the base of the arm and between DAPs of the first few segments. VAPs are wider than long, pentagonal with an obtuse proximal angle, rounded distal margin and straight lateral margins, separate. Arm spines are rounded in cross section and tapering to a blunt rounded tip, rugose but not thorny. First segments have 3 short spines, 4 on next 2 segments; beyond the disc there are 5–6 arm spines, uppermost to as long as a segment, lower spines 2/3 to half as long ( Fig. 7F View FIGURE 7 ). Near the arm tip, the 3 spines become slender, subequal, less than a segment long and have thorns on the ventral side ( Fig. 7G View FIGURE 7 ). Tentacle pores are small with a tiny pointed tentacle scale on proximal segments.

Paratype variations. 4.5–5.5 mm dd ( Fig. 7H–I View FIGURE 7 ). On one broken specimen, a vertical row of 5 flattened teeth are visible with a rounded distal edge. On some specimens there are only 2 lateral oral papillae on some jaws. The tentacle scales are difficult to see and rare on many specimens.

Paratype ossicle description. Proximal LAPs ( Fig. 8A–B View FIGURE 8 ) are approximately as high as long, of rounded outline, tumid, thick, with strongly convex distal edge; ventral edge convex, not protruding; dorsal edge oblique, very weakly concave; outer surface with coarsely meshed stereom, with trabecular intersections transformed into small, inconspicuous tubercles, no vertical striation; outer proximal edge with band of more finely meshed stereom, with a single, poorly defined spur in the dorsal half of the proximal edge. Spine articulations ( Fig. 8C View FIGURE 8 ) are freestanding in a continuous vertical row on a raised distal portion of the LAP, ear-shaped, relatively small, composed of proximally merged dorsal and ventral lobes enclosing a large muscle opening and a smaller nerve opening, with a weakly developed sigmoidal fold. Inner side of LAPs with a large, prominent, moderately well-defined, digit-1-shaped vertebral articular ridge; poorly-defined spur in the dorsal half of the inner distal edge corresponding to the spur on the outer distal edge of the LAP; tentacle notch small, oblique, shallow. Very small, inconspicuous perforations occur close to the ventro-distal tip of the vertebral articular structure.

Vertebrae ( Fig. 8G–K View FIGURE 8 ) compact, tumid, with small, narrow distal and proximal muscle fossae; large, hourglassshaped (streptospondylous) distal and proximal articulations; oblique P-shaped lateral articulation structure corresponding with articular structure on the inner side of the LAP; large, deep dorsal and ventral furrows, with small, inconspicuous podial basins.

Oral plates ( Fig. 8O View FIGURE 8 ) split into distal and proximal halves, approximately as high as long, with adradial muscle fossa lining the ventro-distal edge of articulation area. Dental plates ( Fig. 8P View FIGURE 8 ) are undivided, narrow, rounded, with single row of small, shallow tooth sockets surrounded by weakly-defined protruding ring. Abradial genital plates ( Fig. 8Q View FIGURE 8 ) are almost as long as the adradial ones ( Fig. 8R View FIGURE 8 ), relatively thick, bar-like, without ridges or groves and with a straight adradio-distal tip. Radial shields ( Fig. 8S View FIGURE 8 ) are strongly elongated, isosceles-triangular outline with a slightly oblique proximal tip; no ornamentation on the outer surface. Proximal dorsal arm spines ( Fig. 8D View FIGURE 8 ), ventral arm spines ( Fig. 8E View FIGURE 8 ), tentacle scales ( Fig. 8F View FIGURE 8 ), disc granules ( Fig. 8L View FIGURE 8 ), ventral arm plate ( Fig. 8M View FIGURE 8 ) and dorsal arm plate ( Fig. 8N View FIGURE 8 ) are also figured.

Remarks. This species is similar to the Atlantic species O. baccata Koehler, 1921 . However, that species is generally smaller, to 4.5 m dd, with smaller (0.2 mm dia) disc granules, and distally lobed oral shields ( Paterson 1985). Other similar species include O. vestitus Lyman, 1878 from off southern Chile (273–940 m) and O. mortenseni A.H. Clark, 1916 from the Galapagos (729 m). These differ in having a more even covering of disc granules that have the form of short cylindrical stumps with a crown of thorns. The species named as “ Ophiacantha sp. ” in Manso (2010, fig. 6) is also likely to be either O. vestitus or O. mortenseni . The type of Ophiolebes is O. scorteus Lyman, 1878b from off subantarctic Marion Island (279–576 m) which has not been reported since. The granules on that species are smaller and restricted to the radial shields with only a few occurring marginally.

The other Atlantic species, O. pachyphylax H.L. Clark, 1915 has much longer arm spines (to 2 segments) and obvious disc plates bearing the granules, and O. retecta Koehler, 1895 has DAPs that are split into two sections (also present in O. antarctica Koehler, 1901 ). There are a number of North Pacific species also referred to Ophiolebes by Clark (1911), Matsumoto (1917), Djakonov (1949) and Irimura (1982) but none of these have the low disc granules embedded in thick skin of the present species. The New Zealand species, O. comatulina McKnight, 2003 , has much longer disc spines. All these species require reassessment of their generic placement.

Conversely, Ophiacantha yaldwyni Fell, 1958 from southern Australia and New Zealand is similar morphologically to the current species and is herein transferred to Ophiolebes , sharing the tiny tentacle scale, short arm spines, and conical granules embedded in disc skin ( Fell, 1958). It differs from the new species in having divergent thorns arising from the centre of the disc granules, thorns at the tip of the arm spines and numerous lateral oral papillae and adoral shield spines.

The MD 50 specimens were found epizoic on a black coral ( Fig. 7C View FIGURE 7 ) .

Etymology. Named after H.B. Fell, a pioneer of echinoderm taxonomy and biogeography in New Zealand, who promoted the idea of long distance dispersal around southern oceans on the “West Wind Drift” ( Fell 1962).