Elpidiidae, Theel, 1882

Elpidiidae View in CoL sp. Danielssen and Koren, 1879

Appendix 1, Table S1, Figure S1

Material examined. NMV F296840 About NMV * (1) [IN 2021 V 04 007] .

Diagnosis of IOT material. A single additional specimen lot identified to Elpidiidae . Specimen was severely damaged (in two pieces), opaque pink/orange gelatinous specimen. No real shape retained but with approximately seven darker red tentacles remaining. One specimen piece> 50 mm long and ~ 25 mm wide from shipboard photograph. Irregular branched ossicles, not crosses, large and flat, ~650 μm in diameter, with a short smooth central beam branching into up to eight long (up to ~460 μm) spinous arms, but no apophyses or other vertical structures. Rare additional smoother irregular branched crosses up to 136 μm long, plus Peniagone -style crosses with short apophyses and out-turned arms.

Remarks. No likely species were found in Hansen’s (1975) Elpidiidae key and descriptions, and no similar ossicles are observable in more recent publications. Based on COI and 16S, this specimen is basal to Peniagone . For 16S, it forms a clade with Protelpidia murrayi , Amperima robusta , and Scotoplanes hanseni , but there is no support for this grouping in COI (fig. S1). Without additional material, this specimen is kept at family level for now.

Distribution. This specimen lot only: Indian Ocean, Australian IOT, Christmas Island Territory, Christmas Island SE Stn., 3200–3345 m.

References. Danielssen and Koren (1879), Hansen, (1975), Kremenetskaia et al. (2021).