Amphiura princeps Koehler, 1907: 303 –305, pl. 12 (28–29).— Clark, H.L., 1915 a: 235.— Mortensen, 1936: 285 –286, fig. 22, pl. 7 (10).— Bernasconi, 1965: 150, pl. 1 (1), 2 (1).— Bernasconi & d'Agostino, 1977: 85 –87, pl. 6 (1,2).— Lucchi, 1985: 122, fig. 2, 25–26.
Amphiura joubini.— Bernasconi & d'Agostino, 1977: 80 –82, pl. 7 (3,4).
Material examined. Akademik Knipovich 4: stn 1063, La Paloma, 34 ° 42´S, 52 ° 14´W, 40–45 m, 1967, identified by Bernasconi & d'Agostino (1977) as Amphiura joubini (MACN 27848, n= 15). Akademik Knipovich 4: stn 1065, Cabo Polonio, 34 ° 29´S, 53 ° 0´W, 50–55 m, 1967, identified by Bernasconi & d'Agostino (1977) as Amphiura joubini (MACN 27849, 14). Akademik Knipovich 4: stn 1068, Cabo Polonio, 34 ° 15´S, 52 ° 12´W, 55–62 m, 1967, identified by Bernasconi & d'Agostino (1977) as Amphiura joubini (MACN 27850, 1). Akademik Knipovich 4: stn 1071, Cabo Polonio, 34 ° 22´S, 52 ° 37´W, 36–42 m, 1967, identified by Bernasconi & d'Agostino (1977) as Amphiura joubini (MACN 27847, 30). SAO V: stn 216, Golfo San Matías, 41 ° 13´S, 65 ° 59´W, 36 m, 1971, identified by Bernasconi & d'Agostino (1977) as Amphiura joubini (MACN 27853, 1).
Distribution. Patagonian shelf from the Straits of Magellan to Uruguay, 0– 107 m.
Remarks. The specimens recorded from the Argentinean coast as Amphiura joubini Koehler, 1912 by Bernasconi and d'Agostino (1974) proved upon re-examination to belong to the species Amphiura princeps. Amphiura joubini is an Antarctic species characterised by a spiniform to pointed distal oral papilla, a broadly triangular to spear-head shaped oral shield (widest near the distal margin), long narrow radial shields (> 4 x longer than broad), an absence of disc plates on the ventral surface near the oral shield, and arm spines that can be elongated into a sharp hyaline (glassy) and/or bent to bifurcated tip near the disc. Amphiura princeps on the other hand has a wide, rounded distal oral papilla, an oral shield that is widest near the proximal margin, radial shield approximately 3 times as long as broad, plates on the ventral disc surface and arm spines that can be bent at the tip but are never hyaline. Both species have small disc plates that can appear granular in appearance, especially on the ventral surface. Bernasconi and d'Agostino (1974) separated their “ joubini ” from “ princeps ” by the partially naked disc surface near the oral shield. However, sparse disc plating can also occur in smaller specimens of O. princeps.
Amphiura joubini has also been reported from southern Brazil (Tommasi 1970; Borges et al. 2002) however, it is unclear from the photographs and descriptions whether these animals are also A. princeps or another species. New Zealand records (Fell 1958; McKnight 1967 a) are mis-identifications of Amphiura correcta and Amphioplus ctenacantha (Mills & O’Hara 2013).