Amphiophiura trifolium Hertz, 1927

O’Hara, Timothy D. & Thuy, Ben, 2025, Seamount ophiuroids from the High Seas of the western Indian Ocean, Zootaxa 5718 (1), pp. 1-88 : 25-26

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.