Notonyx A. Milne-Edwards, 1873,

Rahayu, Dwi Listyo, 2011, A new species of Notonyx A. Milne-Edwards 1873 (Crustacea: Decapoda: Brachyura: Goneplacidae) from Maluku, Indonesia, Zootaxa 2982, pp. 33-39: 33-38

publication ID 10.5281/zenodo.207988

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Notonyx A. Milne-Edwards, 1873


Genus Notonyx A. Milne-Edwards, 1873 

Notonyx falcatus  n. sp. ( Fig. 1–4View FIGURE 1View FIGURE 2View FIGURE 3View FIGURE 4)

Material examined. Holotype male, 15.2 × 11 mm ( MZB), Pulau Buntal, Seram Island, Maluku, Indonesia, 03°03' 10 ''S 128 °04' 50 ''S, 29 June 1993. Paratypes, 2 females 16 × 11.2 mm, 8 × 5.8 mm ( ZRC), 1 juvenile female 5 × 4.2 mm ( MZB), same locality as holotype.

Diagnosis. Carapace subquadrilateral, wider than long (1.36 times as wide as long in holotype) ( Figs. 1View FIGURE 1 A, 3 A). Frontal margin slightly bilobed, about 0.33 times carapace width ( Figs. 1View FIGURE 1 A, C, 3 A). Anterolateral margin short, entire, curved, unarmed; posterolateral margin longer ( Figs. 1View FIGURE 1 A, 3 A). Dorsal surface of carapace smooth, without indication of regions except for shallow gastro-cardiac grooves; convex anteriorly, gently convex posteriorly ( Figs. 1View FIGURE 1 A, 3 A). Antennules relatively long, terminal setae reaching cornea ( Figs. 1View FIGURE 1 B, 3 A). Basal antennal joint small, short, positioned on orbital hiatus ( Fig. 1View FIGURE 1 B, C). Eye peduncle moderately long, 0.54 times frontal width, cornea small ( Figs. 1View FIGURE 1 A, C, 3 A). Small gape present between third maxillipeds when closed ( Figs. 1View FIGURE 1 B, 2 A); merus shorter than ischium; antero-external angle of merus forms right-angle ( Fig. 3View FIGURE 3 D). Chelipeds subequal, left larger ( Figs. 1View FIGURE 1 C, 2 B); fingers stout, dactylus smooth, shallow longitudinal groove on outer surface; fixed finger with shallow longitudinal groove medially, low longitudinal keel on ventral margin continues to palm, palm smooth; inner margin of carpus with acute tooth ( Fig. 3View FIGURE 3 C), clump of short setae on inner margin; merus with long, stiff setae on anterior, posterior margins. Ambulatory legs relatively long ( Figs. 1View FIGURE 1 A, B, 3 E), smooth; dactylus with carina on lateral surface; sparse setae on upper, lower margin of propodi, carpi, meri.

Male thoracic sternum relatively broad; surface lightly pitted; sternites 1, 2 fused, separated from sternite 3 by distinct transverse suture; sternites 3, 4 fused with only lateral incision visible ( Figs. 1View FIGURE 1 B, 2 A). Male abdomen triangular, relatively narrow with 7 movable somites including telson; somite 1 underneath carapace, wider than somite 2; somite 2 longitudinally narrow; somite 3 widest; somites 4 to 6 tapering to rounded telson which is slightly longer than somite 6 ( Figs. 1View FIGURE 1 B, 2 A, 3 B). G 1 relatively stout, slightly bent inward on distal two-fifth ( Figs. 4View FIGURE 4 A –C), continue to slightly curve, form hook-like projection, tapering at tip; distolateral part with row of spines, followed by longitudinal smooth area, flanked by row of spines on dorsal and ventral areas, mesial area with numerous short spines. G 2 long ( Fig. 4View FIGURE 4 D, E), much longer than G 1, distal segment longer than basal segment, distal third of distal segment curved inward, tip sickle-shaped, directed anteriorly armed with spiniform setae.

Etymology. The name is derived from the Latin falcatus  , meaning sickle-shaped, alluding to the sickle-shaped of the tip of the G 2.

Remarks. The broad carapace, the relatively long pereopods and the hook-like distal tip the G 1 of Notonyx falcatus  n.sp. suggest this species is closest to N. latus Ng & Clark, 2008  , from Kei Islands, Lesser Sunda Islands, Indonesia and N. sagittifer Ng & Clark, 2010  , from the Philippines. Although the G 1 of these three species posses a hook-like projection distally, this character is diagnostic. In N. falcatus  n. sp. the G 1 is distally bent and curved, tapering to a pointed tip with a row of spines and numerous prominent spines featuring on the distolateral, dorsal and ventral surfaces ( Fig. 4View FIGURE 4 A –C). The G 1 in N. latus  is almost straight for the entire length with the subdistal part being slightly dilated, bent, and end in an elongate truncated tip, the spines been situated on the distal part of the ventral and lateral areas (Ng & Clark 2008: fig. 3). In comparison, the G 1 of N. sagittifer  is gently curved outwards, with the distal part not being elongated, but folded forming a U-shaped gutter-like structure and being distinctly swollen subdistally (Ng & Clark 2010: fig. 3 A –D). The difference in the shape of the G 2 is more significant. In N. latus  and N. sagittifer  , the tip of the G 2 appears S-shaped while that of N. sagittifer  is distally spear-shaped (Ng & Clark 2010: fig. 3 E –H). The G 2 in N. latus  is tapered abruptly to distally form a sharp hook (Ng & Clark 2008: Fig. 4View FIGURE 4). In N. falcatus  n. sp., the G 2 is strongly curved on the distal third, the tip is sickle-shaped and armed with numerous spiniform setae ( Fig. 4View FIGURE 4 D, E).

Other diagnostic characters for N. falcatus  n. sp. include the merus of the third maxilliped being shorter than the ischium ( Fig. 3View FIGURE 3 D) instead of only slightly shorter in N. latus  and N. sagittifer  (Ng & Clark 2008: fig. 2 B; Ng & Clark 2010: fig. 2 A). The male abdomen of N. latus  and N. sagittifer  is also relatively broader (Ng & Clark 2008: fig. 2 E; Ng & Clark 2010: fig. 2 B) than that of N. falcatus  n. sp. ( Fig. 3View FIGURE 3 B). The male G 2 of N. falcatus  n. sp. is comparable to that of N. nitidus A. Milne-Edwards, 1873  in having the distal fifth curved. For N. nitidus  the tip of the G 2 is directed upward ( Clark & Ng 2006, fig. 3 G), while in N. falcatus  n. sp. it is sickle-shaped and directed anteriorly ( Fig. 4View FIGURE 4 D, E). The male G 1 of N. nitidus  is only slightly bent ( Clark & Ng 2006, fig. 3 H, I), instead of hook-shaped in N. falcatus  n. sp. ( Fig. 4View FIGURE 4 A –C). Finally, the carapace of N. nitidus  is proportionately narrower ( Clark & Ng 2006: fig. 2 A, 3 A) than that of N. falcatus  n.sp. ( Fig. 3View FIGURE 3 A).

Distribution. The new species is only reported intertidally from the type locality, Pulau Buntal, Seram island, Maluku, Indonesia.

Discussion. So far six out of 11 Notonyx  species are found in the Lesser Sunda Islands, Indonesia ( Clark & Ng, 2006; Ng & Clark, 2008; Naruse & Maenosono, 2009; Rahayu & Ng, 2010 a, b). Notonyx castroi Rahayu & Ng, 2010  , N. falcatus  n. sp., N. guinotae Rahayu & Ng, 2010  , N. latus  are exclusively found in Indonesian waters. Two other species, N. gigacarcinicus Clark & Ng, 2006  , and N. kumi Naruse & Maenosono, 2009  are recorded from Phuket, Thailand and Japan respectively. Except for N. latus  , the five species from Indonesia were collected on seagrass beds with coarse or fine sand and gravel substrates. The collections were made by digging (ca. about 10–20 cm) and sieving the substrate. The remaining five species have a reported limited distribution: N. nitidus  from New Caledonia; N. angulatus Naruse & Takeda, 2010  , Japan; N. rayneri Ng & Clark, 2010  , Fiji; N. sagittifer  , the Philippines and N. vitreus Alcock, 1900  was reported from Indian Ocean.


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Zoological Reference Collection, National University of Singapore