Oneirophanta sp.

Oneirophanta sp. MoV. 7331

Material examined. NMV F308334 About NMV * (1) [IN 2022 V 08 196] .

Diagnosis of IOT material. Body elongated, semicylindrical, equal width for most of its length. Strongly raised dorsally, flattened ventrally, with rounded oral and anal ends. Medium-sized specimen, 130 mm long, 37 mm wide and 22 mm high (preserved). Dirty white with black and brown patches (likely an artifact of the station). Skin thick, firm, and wrinkled once preserved. Anus ventral and terminal. Mouth ventral and terminal with 20 tentacles on short stalks, non-retractable, roughly circular and dark brown at tips, and lacking marginal knobs. Papillae of variable size, with cone shaped base and tapered at tips. Dorsal surface not crowded. Dorsal radii with well-spaced large and small papillae in single rows (10 and 11) on each. Single rows of ventrolateral papillae (6 and 8 per side), plus an additional one anteriorly for both. Ventrally, zigzag rows of extended tube feet on each side. Once preserved outer nine tube feet appear slightly larger than inner 8–9 on each side, all robust with rounded ends. Mostly bare midventrally with just four smaller tube feet in a zigzag pattern towards the anal end. Midventral line darker than the rest of the ventral surface and slightly indented. Body wall ossicles rods and crosses with branching, perforated or spatulated ends, perforations in some ends almost creating thin plates, no complete plates seen. Tube feet and papillae with same and some less branched crosses and rods. No long spatulated rods in papillae. Tentacles smooth to rarely spinous irregular rods with branched ends.

Remarks. This single specimen was from a station with manganese nodules so colouring and texture may be artifacts. While some broken spatulated crosses were seen, it lacks the clustered spatulated papillae rods of Oneirophanta setigera . External morphology resembles the subspecies Oneirophanta mutabilis affinis Ludwig, 1894 , particularly the reduced papillae version represented in Hansen, 1975 (fig 6, p33, bottom picture). Tentacles lacking marginal knobs and the number of dorsal and ventrolateral papillae also fit within the range of O. mutabilis affinis , but there are far fewer tube feet in Oneirophanta sp. MoV. 7331 (up to 9 each side compared to 15–20). Rod ossicles in these specimens agree with type illustrations for O. mutabilis affinis in Ludwig, 1894 (pl. 7, fig. 8–13) of rods with perforated to spatulated ends, but Oneirophanta sp. MoV. 7331 also includes some broken spatulated crosses and more importantly lacks the “robust and rather small plates” noted as the dominant ossicle for that subspecies ( Hansen, 1975). O. mutabilis affinis has previously been restricted to the eastern Pacific, so it is likely that this IOT specimen is a new species, but the authors are reluctant to identify it past OTU level Oneirophanta sp. MoV. 7331 without additional study of the literature, and comparative specimen and genetic samples.

Distribution. This specimen lot only: Indian Ocean, Australian IOT, Cocos (Keeling) Islands Territory, Cocos Abyssal Stn., 3431–5414 m.

References (for genus). Hansen (1975), Ludwig (1894).