Ophiectodia melvillei, O’Hara & Thuy, 2025

O’Hara, Timothy D. & Thuy, Ben, 2025, Seamount ophiuroids from the High Seas of the western Indian Ocean, Zootaxa 5718 (1), pp. 1-88 : 41-44

publication ID	https://doi.org/10.11646/zootaxa.5718.1.1
publication LSID	lsid:zoobank.org:pub:A97521F7-2BF1-4840-8C22-03AF6B0AE2D2
persistent identifier	https://treatment.plazi.org/id/3724530A-FFF3-A850-FF1A-A7955A1AFA63
treatment provided by	Plazi
scientific name	Ophiectodia melvillei
status	sp. nov.

Treatment

Ophiectodia melvillei sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:

Fig. 14h–k View FIGURE 14 , 15 View FIGURE 15

TYPE LOCALITY. Melville Bank, 38° 30.081´S, 46° 45.78´E GoogleMaps to 38° 29.77´S, 46° 45.58´E, 1364 m

TYPE MATERIAL. — JC066 : stn 5-24, Melville Bank, 38° 30.081´S, 46° 45.78´E to 38° 29.77´S, 46° 45.58´E, 1364 m, 26/11/2011, holotype: 1 ( NHMUK 2025.40 About NHMUK ) GoogleMaps ; paratype: 1 ( MV F321044 ) ( DNA code= JC066-3284 ) ; paratype: 1 ( NHMUK 2025.39 About NHMUK ) ( DNA code= JC066-3275 ) .

OTHER STUDY MATERIAL. Ophiectodia cf melvillei : JC066: stn 8-22, Atlantis Bank, 32° 42.225´S, 57° 18.02´E to 32° 42.59´S, 57° 17.01´E, 1000 m, 13/12/2011: 1 ( NHMUK 2025.41 About NHMUK ) GoogleMaps ( DNA code= JC066-3736 ) .

COMPARATIVE MATERIAL EXAMINED. Ophiectodia imago ( Lyman, 1878) : PROTEKER 1/trois bergers, Ilot des 3 Bergers, 49° 17.382´S, 69° 42.666´E, 5–20 m, 28/12/2011, MNHN GoogleMaps IE.2013.16281 ( DNA code= TOH92 - IE.2013.16281). Ophiectodia opulenta ( Koehler, 1908) : PS61 ANT-XIX/4 ( ANDEEP)/132-3, 65° 17.88´S, 53° 22.88´W to 65° 17.35´S, 53° 22.89´W, 2087– 2084 m, 6/3/2002 GoogleMaps , CASIZ 161433 ( DNA code= CAS161433 About CAS ) .

Diagnosis. Disc covered in small conical granules terminating in a few thorns, middle surface of bar-like radial shields naked, some granules on distal edge of basal DAPs. Oral shields wider than long. 4–7 spiniform oral papillae. Five arms with to 9 arm spines on each side, less than a segment in length, minutely thorny, 1 tiny, pointed tentacle scale, absent basally.

Description. Holotype 8 mm dd, disc pentagonal to round, covered in thin round perforated disc scales with dense (but separate) tiny conical disc granules with a few short thorns at the apex, 0.10–0.15 mm wide, 1–2x as high as wide, a small narrow naked area over the mid-part of the radial shield, granules extend onto the dorsal arm;

granules covering entire ventral disc surface, but smaller and conical to hemispherical near the genital slit and oral shields; oral shield lozenge-shaped with rounded angles, proximal and distal angle a little lobed, 2x as wide as long; adoral shields 2x as wide as long, separated interradially by a small decalcified area, do not continue distally around the lateral edges of the oral shields; jaws wider than long, bearing 4–7 spiniform oral papillae, some suboral in position, 2–3x as long as wide, inner ones pointed, distal ones more rounded, minutely thorny; 4 teeth, 3 ventralmost with a wide truncate distal edge, dorsal one thinner, more spine like; 2nd oral tentacle opening within the jaw slit.

Arms five, exceeding 37 mm in length; DAPs wider than long, fan-shaped to triangular, with an obtuse proximal angle and convex distal margin, separate, with 1–2 rows of disc granules occurring around the edge of the 3 basal DAPs, then just on the distal edge of the succeeding 3 plates; VAP1 heart-shaped with proximolateral lobes, narrow distal edge that is contiguous with VAP2, succeeding VAPs broadly triangular, 2x as wide as long, with an obtuse proximal angle and rounded distal edge, slightly notched laterally for the podial pores, just contiguous, becoming as wide as long by the 8th segment and then longer than wide; to 9 short minutely-thorny arm spines, middle one longest but less than a segment in length, 3x as long as wide, blunt apex, 2 spines on the first arm segment, 3 on the 2nd and 5 on the 3rd, distally the lowest arm spine has ventral thorns that give it a hook-shape; one tiny pointed tentacle scale about 1/5 the segment in length with 1–2 terminal thorns, absent for the first 14 segments or so (the lower arm spine bent over the pore), but then persisting until end of arm.

Paratypes MV F321044 ( 6 mm dd) and 6.5 mm dd) are similar but differ in having fewer arm spines (up to 7) that typically extend to less than 1/2 the segment in length, the number of granules along the distal DAP edge reduced to 1 by the 4th segment. Paratype (NHMUK 2025.39) vertebrae ( Fig. 15e–i View FIGURE 15 ) with streptospondylous hour-glass articulations, ventral fossae positioned near distal margin and the whole vertebra appears attenuated proximally. LAPs ( Fig. 15a–d View FIGURE 15 ) longer dorsally than ventrally, with dense perforated but not striated stereom, and a clear demarcation to the ridge of spine articulations which has a more open stereom network, articulations horseshoe-shaped with a distal opening, slightly more thickened dorsally, enclosing muscle and nerve pores that are separated by a vertical septum. Dental plate ( Fig. 15l View FIGURE 15 ) oblong shaped with at least 4 sunken tooth articulation points, ventrally smallest. Oral plates ( Fig. 15j–k View FIGURE 15 ) short, only as wide as long.

Distribution. Melville Bank ( 1364 m),?Coral Seamount ( 1000 m).

Remarks. Our genetic evidence places this species within Ophiectodia , sister to all the other described species. Its morphology is also consistent with Ophiectodia by having small dense disc spines, more than 3 oral papillae, numerous arm spines and a tiny tentacle scale. The new species differs from the other described species ( O. enopla , O. imago , O. opulenta ) by having very short arm spines that do not exceed a segment in length. The upper arm spine on the other species exceeds 2 segments in length. Ophiectodia enopla further differs in having granule-shaped disc spines (in adults) covered in multiple tiny points, and O. opulenta has 6–7 arms, although it does not appear to be fissiparous.

We have also included a small specimen (NHMUK 2025.41, 4 mm dd) from the Atlantis Bank ( Fig 14l–n View FIGURE 14 ) in this species. Its DNA is divergent from the two Melville Bank samples, and it differs morphologically in having granule-shaped disc spines with some tiny terminal thorns, a larger section of the radial shield that is exposed, to 6 short arm spines, and a smaller oral shield, only as wide as long. With only one small specimen it is unclear whether this represents a distinct species or a juvenile of O. melvillei . Ophiacanthid disc spines are known to alter shape with growth from juvenile to adult (see O. enopla ).

Etymology. Named after Melville Bank, the type locality.