Amphiophiura trifolium Hertz, 1927

Amphiophiura trifolium Hertz, 1927b: 78–79, fig. 3, pl. 6(14–15). — Clark, H.L., 1939: 108–109. — Clark, A.M., 1974: 476. — Clark, A.M. & Courtman-Stock, 1976: 187. — Guille & Vadon, 1986: 181. — Olbers et al. 2019: 94–95, fig. 72–73.

STUDY 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: 4 (MNHN IE.2016.1368) (DNA code= IE.2016.1368) .

COMPARATIVE MATERIAL EXAMINED. Amphiophiura ornata (Lyman, 1878): Challenger/216, 2° 56´N, 134° 11´E, 3720 m, 16/2/1875, holotype, NHMUK 1882.12.23.411. IN2017_V03/101, off Moreton Bay, 26° 56.748´S, 153° 56.7´E to 26° 58.272´S, 153° 57.072´E, 2520–2576 m, 9/6/2017, MV F237932 (DNA code=F237932). Amphiophiura radiata (Lyman, 1878): Challenger/205, west of Luzon Is, 16° 42´N, 119° 22´E, 1953 m, 13/11/1874, holotype, NHMUK 1882.12.23.422. TAN0205/21, Ngatorirangi Seamount, 33° 42.082´S, 179° 51.294´E to 33° 42.469´S, 179° 50.751´E, 1627– 1330 m, 14/4/2002, NIWA 67141 (DNA code= NIWA 67141).

Description. Disc to 8 mm dd, radial shields 1/5 dd, contiguous over much of their length, large marginal interradial plate, other disc covered in numerous small overlapping scales, primaries larger; arm comb comprised of small spatulate papillae becoming a row of close set square genital papillae ventrally, some opposing spines on basal DAPs, DAPs ovoid at first become separate by 4th plate, with long tapering proximal borders and a convex distal border; tiny then 3 tiny arm spines, 10th segment long, middle one becoming hooked distally; oral shields trefoil as wide as long, numerous small ventral disc scales, oral frame a little sunken.

Distribution. W Indian Ocean (949–2727 m), Walters Shoal (1865–2058 m).

Remarks. These specimens conform to the description of A. trifolium known from the western Indian Ocean. However, they are also very similar to A. radiata (Lyman, 1878) from the Indo-Pacific and more research is required to test whether these species should remain distinct. Amphiophiura ornata (Lyman, 1878) is also related, differing in having contiguous DAPs. Amphiophiura trifolium, A. radiata and A. ornata form a distinct clade on our phylogeny but more work is required to determine morphological characters that could define this clade as a new genus.