Amphiura cf. natalensis

Amphiura cf. natalensis

Fig. 26d–g View FIGURE 26

STUDY MATERIAL. — JC066 : stn 4-12, Coral seamount, 41° 22.333´S, 42° 54.066´E to 41° 23´S, 42° 54.1´E, 730 m, 16/11/2011: 1 ( NHMUK 2025.22 About NHMUK ) ( DNA code= JC066-592 ); 1 ( NHMUK 2025.21 About NHMUK ) GoogleMaps .

COMPARATIVE MATERIAL EXAMINED. Amphiura dejectoides H.L. Clark, 1939 : MIRIKY/CP3247, au large de la Baie Mahajamba, 14° 50.39´S, 46° 59.1498´E to 14° 49.86´S, 47° 0.0198´E, 349–442 m, 7/7/2009, MNHN IE.2007.413 ( DNA code=IE.2007.413). Amphiura ficta Koehler, 1910 : MIRIKY/CP3223, entre Nosy-bé et Banc du Leven, 12° 47.94´S, 48° 11.28´E to 12° 46.26´S, 48° 11.2602´E, 430–488 m, 2/7/2009, MNHN IE.2007.1260 ( DNA code=IE.2007.1260). Amphiura grandisquama Lyman, 1869 : Johnson Sea Link II/JSL-II-3665, Miami Terrace, 26° 3.8757´N, 79° 50.9349´W, 329–343 m, 22/9/2004, MV F254609 ( DNA code=F254609). Amphiura iris Lyman, 1879 : SE-1518/14, Kumano Sea, S of Shirna Peninsula, Mie Pref, 34° 2.8´N, 136° 53.2´E, 725 m, 9/10/2015, NSMT E9100 ( DNA code=NSMT E9100). Amphiura spinipes Mortensen, 1924 : TAN1007/104, Rumble II West seamount, 35° 21.732´S, 178° 31.548´E to 35° 21.582´S, 178° 31.848´E, 1287–1378 m, 6/6/2010, NIWA 70686 ( DNA code=70686).

Description. Disc to 3.8 mm dd, disc covered in tiny disc scales, primaries distinct, a little larger than others, widely separated, disc scales near the centre of the disc becoming isolated, not contiguous with neighbours, radial shields 1/6–1/7 dd, divergent proximally, 3x as long as wide; disc scales persist ventrally until the oral shield; oral shield round triangular, 1.5x as wide as long, no distal lobe; adoral shields triangular, proximolateral to the oral shields, just meeting or separate interradially; distal oral papillae leaf-shaped, 1.5–2.0x as high as wide; DAPs ovoid, as wide as long, contiguous; VAPs 1.5x longer than wide, with convergent proximal sides, incised lateral ones (around pores) and a straight lateral edge with rounded corners; basally 6 arm spines, upper and lowest longest, bluntly pointed, no apical thorns, by the centre of the arm the lowest is 1.5x segment in length, almost 2x the size of the 2nd ventralmost, capitate, upper is 2nd longest, 3 middle spines becoming 2 middle spines by the end of the arm; one large flat oval tentacle scale. The LAPs ( Fig. 26d–e View FIGURE 26 ) are curved with extensions meeting on the dorsal and ventral radial midline; the stereom is densest just proximal to the line of arm spine articulations, articulations with two horizontal raised lips with gaps at each lateral end. Vertebrae ( Fig. 26f View FIGURE 26 ) with pronounced distal articulation, with a small heart-shaped zygosphene, and a deep furrow ventrally.

Distribution. Coral Seamount ( 730 m)

Remarks. The Coral Seamount specimens have the distinctive long ventral arm spines and single oval tentacle scale typical of the A. magellanica - A. grandisquama group of Amphiura . They are closest to the descriptions of A. grandisquama natalensis Mortensen, 1933b known from off the Indian Ocean coastline of South Africa. The South African specimens (< 4 mm dd) have been described as having up to 5 rather than 6 arm spines, no primary plates (although they appear to be present in photos in Olbers et al. 2019 fig. 229), and longer ventral arm spines (to 3 segments in length). More specimens from the region are required to determine species boundaries.

Other similar bathyal species from the Indo-Pacific include A. iris Lyman, 1879 from off Japan which has only 4 arm spines. It was synonymised by Paterson (1985) with the Atlantic species A. grandisquama Lyman, 1869 , however, our DNA evidence indicates that specimens from Japan are polyphyletic with respect to Atlantic specimens and should be retained as a separate species pending a larger revision. Amphiura iridoides Matsumoto, 1917 from off Japan ( 580 m) has much larger disc scales and radial shields. Amphiura dejecta Koehler, 1922a from off Borneo ( 558 m) has larger disc plates and radial shields and prominent, sometimes contiguous) primary plates. Amphiura glabra Lyman, 1879 (see below) from the Philippines ( 930 m) has much larger radial shields and a naked ventral disc. In shallower waters, A. dejectoides from the Western Indian Ocean has arm spines with squared-off minutely thorny tips.