Ophiuroglypha atlantis, O’Hara & Thuy, 2025

Ophiuroglypha atlantis sp. nov.

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Fig. 10a–l View FIGURE 10

TYPE LOCALITY. Atlantis Bank, 32° 42.658´S, 57° 16.371´E GoogleMaps to 32° 42.64´S, 57° 17.58´E, 707 m

TYPE MATERIAL. — JC066 : stn 8-3, Atlantis Bank, 32° 42.658´S, 57° 16.371´E to 32° 42.64´S, 57° 17.58´E, 707 m, 9/12/2011, holotype: 1 ( NHMUK 2025.64 About NHMUK ) GoogleMaps ; paratype: 1 ( MV F321045 ) ( DNA code= JC066-3639 ) .

OTHER STUDY MATERIAL. Ophiuroglypha sp : JC066/4-20, Coral seamount, 41° 22.35´S, 42° 54.64´E, 732 m, 17/11/2011 GoogleMaps , NHMUK.2025.63 (1).

COMPARATIVE MATERIAL EXAMINED. Ophiuroglypha sp. MoV.7376 KANADEEP2/ PL740 _ASPI-6, Mont D, 23° 34.417´S, 169° 36.953´E, 667 m, 6/9/2019, MNHN GoogleMaps IE.2019.2921 ( DNA code=IE.2019.2921).

Diagnosis. Radial shields contiguous for distal half of plates. Disc plates polygonal, variable in size. Arm comb with conical to hemispherical papillae, continue along genital slit until mid-radius. Oral shield longer than wide, concave laterally. DAPs rhomboid, contiguous. VAPs contiguous for basal 5 plates, 1 st and 2 nd VAPs contiguous for over half their width. 3 short peg-like arm spines, to 1/4 segment in length, middle one becoming upturned and hook-like distally.

Description. Holotype 12 mm dd, disc indented interradially, thick rounded margin, covered in round to polygonal imbricating scales, centrodorsal pentagonal, primary and secondary plates larger and surrounded by smaller scales, marginal interradial plate not particularly enlarged, 6–7 plates between centrodorsal and radial shields; radial shields 1/5 dd, egg-shaped, with flattened distal edge, tapering proximally, contiguous radially for 1/2 plate, separated interradially by 3 scales; 5–6 rows of smaller disc scales ventrally; arm comb consists of hemispherical to conical papillae, not contiguous over dorsal arm base, becoming granule-like ventrally, persisting 1/2 way down bursal silt towards oral shield. Oral shield pentagonal, just longer than wide, with slightly convex distal margin, slightly concave distolateral sides and tapered proximally to a rounded angle; adoral shields narrow, 5.5 times longer than wide, extending to 1/2 way down oral shield, contiguous (or sometime sunken) interradially, contiguous with the first LAP distally; visible section of the oral plate sausage-shaped, leaving a small triangular decalcified area between them and the oral shields; 4–5 oral papillae along jaw edge, inner ones pointed, outer ones wide and rectangular; teeth conical to triangular, 4 in the main series, in addition a smaller apical tooth sits ventral to the oral papillae; 2nd oral tentacle pore opens outside the jaw slit with 5–6 abradial and 4 adradial scales, the outer adradial scales are larger and sit on the lateroproximal edge of the first VAP, the inner 2 arise from the ventral tentacle compartment which form the distal edge of the jaw slit.

First 1–2 DAPs rhomboid, visible underneath the arm combs, next DAP 3 times as wide as long with a convex distal edge and straight proximal one, succeeding plates becoming rhomboid then rounded triangular, with a straight proximal edge, divergent lateral sides and convex distal edge, distally 2x longer than wide, contiguous until near arm tip; LAP with an obtuse distal angle, straight lateral sides, and ventral part that is curved under the arm; 1st VAP 2x wider than long, hexagonal, a small gap between the first VAP and LAP, 2nd VAP more rhomboid, as wide as long, becoming a wide triangular shape by 5th segment with rounded angles ( Fig. 10k View FIGURE 10 ), separate from the 5th VAP, developing notched proximolateral edges by the 8th VAP ( Fig. 10g View FIGURE 10 ), 4x as wide as long distally and widely separated; 3 spaced spindle-like to cylindrical arm spines on the ventral half of the LAP, 1/4x segment length, middle one develops a rudimentary hook-tip distally; tentacle pore adjacent to the 2nd VAP with 6 abradial (on LAP) and 5 adradial (on VAP) tentacle scales, the distal adradial one is much wider than the others, forming the distal edge to the pore, appears like an accessory plate that separates the VAP and LAP; only a smaller version of this plate and 2–3 abradial ones persist by the 12th VAP, and only 1 pointed abradial scale distally. Colour (preserved) white.

Paratype 10 mm dd, similar to holotype. LAP ( Fig. 10h–j View FIGURE 10 ) with dense stereom, transversely striated where it sits under its proximal neighbour, arm spine articulation very simple with small holes for both the muscle attachment and nerve ( Fig. 10j View FIGURE 10 ); vertebrae with tall dorsal muscle fossae and well-developed ventral podia basins, strongly grooved ventrally, with tall narrow zygosphene ( Fig. 10d View FIGURE 10 ).

Distribution. Atlantis Bank, SW Indian Ridge ( 707 m).

Remarks. This species possesses the enlarged plate-like adradial tentacle scale and separate arm combs that are characteristic of the Ophiuroglypha irrorata complex of species. This complex has been treated as a single morpho-species by many taxonomists, with an extensive list of synonyms (e.g. Madsen 1967). However, DNA evidence indicates that it is an extensive complex of many sibling species (see tree in Christodoulou et al. 2020), and characters such as the nature of the adradial tentacle scale (hinged vs flat), disc margin (sharp vs rounded), the size and position of the radial shields, the extent of the arm comb (limited to the disc margin or extending dorsally), and number (3 to many) and position (spaced or bunched on the lower portion of the LAP) of the arm spines may provide species-level diagnoses (see also Paterson 1985). Assigning names to the DNA clades requires further research. In particular, we require DNA samples from near the type locality of O. irrorata off western South Africa in 3534 m.

The new species appears to differ from existing species in having a combination of contiguous radial shields, separate dorsal arm combs, an oral shield that is longer than wide, a persistent enlarged adradial tentacle scale, and 3 widely separated arm spines. It is closest genetically to an upper bathyal specimen from New Caledonia (IE.2019.2921) which also appears to be a new species ( O. sp.MoV.7376).

A smaller 6 mm dd specimen from the Coral Seamount (NHMUK 2025.63, Fig. 13i–k View FIGURE 13 ) is probably a distinct species. It has large irregular radial shields, arm spines that can reach a segment in length, and lacks the plate-like adradial tentacle scale. Better material is required to understand its relationships.

Etymology. Named after Atlantis seamount, the type locality.