Amphiophiura litvinovae, O’Hara & Thuy, 2025

Amphiophiura litvinovae sp. nov.

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Fig. 13a–h View FIGURE 13

TYPE LOCALITY. Walters shoal, Plaine Sud, 33° 56.85´S, 44° 0.07´E GoogleMaps to 33° 58.8´S, 43° 55.3999´E, 1865–2058 m.

TYPE MATERIAL. — MD208 : stn CP4915, Walters shoal, Plaine Sud, 33° 56.85´S, 44° 0.07´E to 33° 58.8´S, 43° 55.3999´E, 1865–2058 m, 12/5/2017: holotype ( MNHN IE.2016.1369) ( DNA code= IE.2016.1369) GoogleMaps .

COMPARATIVE MATERIAL EXAMINED. Amphiophiura cf. improba EBISCO /CP2652, SE Fairway, 21° 24´S, 162° 37.0001´E, 1019–1147 m, 23/10/2005, MNHN GoogleMaps IE.2007.5248 ( DNA code= IE.2007.5248).

Amphiophiura improba ( Koehler, 1904) View in CoL : Siboga /226, Banda Sea, between Lucipara and Mai Islands, Mid channel between the Lacipara and Schildpad Islands , 5° 26.7´S, 127° 36.5´E, 1595 m, 11/11/1899, 2 syntypes, ZMA E2400 View Materials GoogleMaps . KANACONO/CP4751, N Mont Antigonia , 23° 19.3´S, 167° 56.77´E to 23° 21.42´S, 167° 57.4603´E, 946–998 m, 25/8/2016, MNHN IE GoogleMaps . 2013.11563 ( DNA code= IE.2013.11563). KANADEEP2/CP5101, Stylaster , 23° 24´S, 168° 31.1´E, 1190–1194 m, 30/9/2019, MNHN IE GoogleMaps .2019.3328 ( DNA code=IE.2019.3328).

Diagnosis. Disc with large (1/6x dd) contiguous radial shields and smaller disc scales, primary plates not obvious. Spiniform to conical arm comb papillae. Ventral interradial area covered by a large oral shield and some smaller marginal scales. Arm carinate in cross-section. 3 sharply pointed arm spines on the ventral half of the LAP, to 2/5 segment in length.

Description. Holotype 6.5 mm dd, disc pentagonal, fully contiguous radials, 1/6x dd, disc plates small, no evident primaries, an enlarged marginal plate with small ones on either side, several transverse rows of disc plates laterally, arm comb conical to spiniform, genital papillae smaller with a sharp point, continuing along bursal slit 1/2 way to the oral shield; oral shield large, taking up the majority of the ventral disc surface, egg-shaped, tapered proximally into an acute point, not incised or trefoil, adoral shields small and narrow, 3.5x as long as wide, only extending along the proximal end of the oral shields, meet interradially; exposed section of oral plate larger than adorals, roughly rhomboid, contiguous for 1/2 their length interradially; bluntly pointed teeth, a little longer than wide, inner oral papillae similar but smaller, distal papillae becoming low and wide, all occurring on the oral plate; 2nd oral tentacle pore elliptical, adjacent to 1st VAP, with 2 adradial and 3 abradial rounded scales not enclosing pore.

Arms triangular in cross section, narrower dorsally than ventrally, first and 2nd DAP 2.5x as wide as long, succeeding plates longer, basal DAPs are rhomboid, then succeeding plates becoming ovoid, becoming separated by the 11th DAP; first VAP roughly triangular, tapering proximally, with a concave distal border and rounded proximodistal corners, a little wider than long; 2nd VAP rhomboid, also with a central concave margin to distal border, contiguous, subsequent plates more hourglass-shaped, with incised lateral sides, acute angle proximally and convex distal margin, separate from the 7th VAP; 3 arm spines on lower half of arms, 2/5 segment in length, terminate in a blunt to sharp point. Basal tentacle pores large elongate and open, with 4 semicircular to spatulate abradial scales and 2–3 smaller ones adradially (on VAP), by 6th VAP 2–3 abradial and one rim-like adradial scales, reduced to a single abradial scale by the 11th VAP. Colour (preserved) brown.

Ossicles. LAPs ( Fig. 13d–e View FIGURE 13 ) quadrangular in lateral view, with a bent lower section that meets the opposite plate on the ventral midline, external stereom regularly perforated; arm spine articulations along the distal edge, slightly raised circular holes; VAPs ( Fig. 13f View FIGURE 13 ) with low transverse ridges that are separated by rows of perforations; vertebrae ( Fig. 13h View FIGURE 13 ) zygospondylous, with elongate zygosphene and reduced zygocondyles on distal face.

Distribution. Walters Shoal ( 1865–2058 m).

Remarks. This sample is morphologically similar to specimens of Amphiophiura improba ( Koehler, 1904) from the Indo-Pacific region. Both have similar dorsal disc plating and carinate arms. The holotype of A. improba differs in having only 2 arm spines and smaller disc scales that are not observable from the ventral side. There is another undescribed species ( A. cf. improba ) from the SW Pacific with one large unbroken marginal ventral disc plate (rather than a number of smaller plates) and up to 4 arm spines. The DNA sequence of the Walters Shoal specimen is divergent from both these species, justifying the description of a new species.

Etymology. Named after Nina Litvinova, former ophiuroid specialist at the P.P. Shirshov Institute of Oceanography, Moscow, who worked extensively on deep-sea ophiuroids and Amphiophiura in particular.