Figures 13–14

Material examined. 1 non-ovigerous female (or early preparatory male?), 2.96 mm, station TD-8, 39º15.54’– 39º17.01’N 144º45.37’– 144º42.46’E, 5762–5733 metres, 4 m ORE beam trawl, 29 September 2001. 1 preparatory male, 2.56 mm, station TD-7, 38°47.93’– 38°45.87’N 144°08.07’– 144°07.89’E, 7340–7433 metres, 30 September 2001.

Remarks. This is a fairly slender species, 7.2–7.9 times as long as broad, but with a relatively short cephalothorax compared to other Akanthophoreus species (Figs 13 A). It is further characterized by thick, pectinate, antennular setae (Fig. 13 D), an elongate uropod basal article (Fig. 13 G) as seen in Paraleptognathia brachiata (Hansen, 1913), a cheliped carpus without shield (Fig. 14 A), a stout pereopod 1 with very long meral and carpal pectinate spiniform setae (Fig. 14 B), these two articles also with a thin dorsal seta, and pereopods 4–6 (Fig. 14 C) with long propodal pectinate setae.

Distribution. Japan Trench, 5733–7433 metres.

Largely because of these characters, this species is only provisionally and tentatively assigned to Akanthophoreus, as it may represent a separate, but closely related, genus: the most similar described species appears to be the equally hadal Biarticulata parabranchiata (Kudinova-Pasternak, 1977) from the Palau Trench, 7000–7170 metres. Another extremely similar, but undescribed species, has been recorded from the abyssal NE Atlantic (as ‘ Leptognathia brachiata Hansen, 1913 ’) by Holdich & Bird (1985) and which has Akanthophoreus -like mandibular molars, not dissimilar to those of B. parabranchiata.