Polyonyx triunguiculatus Zehntner, 1894

Osawa, Masayuki, 2007, Porcellanidae (Crustacea: Decapoda: Anomura) from New Caledonia and the Loyalty Islands, Zootaxa 1548, pp. 1-49 : 38

Polyonyx triunguiculatus Zehntner, 1894

( Fig. 12 )

Polyonyx triunguiculatus Zehntner, 1894: 185 (type locality: Amboina).— Haig, 1979: 133, figs. 23–25.— Lewinsohn, 1969: 158, fig. 35.— Yang, 1996: 262, fig. 4.

Polyonyx acutifrons de Man, 1896: 384 (type locality: Atjeh, Sumatra); 1898: pl. 32, figs. 49, 49a–d.

Material examined. New Caledonia. Canala Bay, Mackau Port, 0 m, mangroves, 30 Jul. 1997, coll. B. Richer de Forges, 2 males CL 4.2, 4.7 mm, 1 ovig. female CL 4.8 mm.

Loyalty Islands. Lifou Island. Santal Bay. Atelier LIFOU. St. 1429 (St. 1), Esao, 20°47.5’S, 167°07.1’E, 8–18 m, 24 Nov. 2000, 1 ovig. female CL 2.7 mm. St. 1420 (St. 26B), Chépénéhé, 20°47.7’S, 167°09.35’E, 4–5 m, 20 Nov. 2000, 1 ovig. female CL 2.5 mm.

Remarks. Polyonyx triunguiculatus is distinguished from the two most similar congeners, P. biunguiculatus and P. obesulus , by the well developed, narrow median lobe of the rostrum ( Fig. 12 B), merus of the cheliped with a broad lobe on the distal dorsomesial margin ( Fig. 12 C), and palm with a distinct, longitudinal crest on the ventral surface ( Fig. 12 D). The median lobe of the rostrum of the carapace of P. triunguiculatus is strongly bent ventrally, so the anterior margin is occasionally concave medially in dorsal view ( Fig. 12 A).

The dactyli of the ambulatory legs have one or two corneous spines on the flexor margin ( Fig. 12 E–G).

Distribution. Nansha Islands in South China Sea, Moluccas, Sumatra, Singapore, Indian Ocean from Gulf of Thailand and Western Australia to Red Sea and Madagascar. Shallow water to about 145 m, often on coral reefs ( Haig 1979; Yang & Naiyanetr 1997). This is the first record of P. triunguiculatus from the southwestern Pacific Ocean. The specimens examined were collected at depths of 0–18 m in New Caledonia and the Loyalty Islands.

Figures

FIGURE 12. Polyonyx triunguiculatus Zehntner, 1894, ovig. female, CL 2.7 mm, Loyalty Islands, St. 1429. A, carapace, and ocular and antennal peduncles, dorsal view; B, rostrum, anterior view; C, larger cheliped, dorsal view; D, same, chela, ventral view; E, left first ambulatory leg, lateral view; F, same, dactylus and distal part of propodus, lateral view; G, left second ambulatory leg, actylus and distal part of propodus, lateral view. Scales equal 1.0 mm.