Notonyx rayneri, Ng, Peter K. L. & Clark, Paul F., 2010

Ng, Peter K. L. & Clark, Paul F., 2010, Two new species of Notonyx A. Milne-Edwards, 1873 (Crustacea: Decapoda: Brachyura: Goneplacidae) from the Philippines and Fiji, Zootaxa 2509, pp. 30-38 : 33-38

Notonyx rayneri n. sp.

( Figs. 4–6 )

Notonyx nitidus – Balss 1938: 74 (not Notonyx nitidus A. Milne-Edwards, 1873 ).

Material examined. Holotype male (17.30 × 10.60 mm) (NHM 1858.172), stn 529, island of Vanua Levu, Nandi, Fiji, presented by Admiralty, coll. F. N. Rayner, voyage of HMS Herald.

Diagnosis. Holotype: carapace ( Fig. 4 A, B) transversely subrectangular, 1.63 × wider than long, frontal margin almost straight. Anterolateral margin short, entire, unarmed; posterolateral margin gently concave, slightly diverging towards posterior part. Dorsal surface of carapace smooth, without indication of regions except for relatively shallow gastro-cardiac grooves; dorsal surface convex anteriorly, gently convex posteriorly. Eyes filling orbit ( Fig. 4 C); cornea pigmented, small. Small gape present between third maxillipeds ( Fig. 5 A) when closed; merus quadrate, anterior margin gently concave, slightly shorter than ischium; anteroexternal angle of merus just above tip of exopod. Chela ( Fig. 4 D, E) with outer surfaces almost smooth, punctate in parts, ventral margin with prominent keel extending almost to tip of finger; dorsal margin of propodus smooth, unarmed; inner margin of carpus with very low tooth, inner margin denticulate. Walking legs ( Fig. 4 A) relatively short. Thoracic sternum relatively broad; surface pitted; sternites 1, 2 completely fused, separated from sternite 3 by prominent transverse suture; sternites 3, 4 fused except for lateral parts of sutures. Male abdomen ( Fig. 5 B) relatively broad, third somite broadest; telson triangular, lateral margins gently sinuous. G1 ( Fig. 6 A–D) relatively slender, gently curved outwards, subdistal part with low hump-like structure, surface lined with numerous small spines, distal part not prominently elongated; outer lower margin with prominent spur-like projection. G2 ( Fig. 6 E, F) sinuous, longer than G1, distal segment longer than basal segment; junction between distal, subdistal segments with concave surface surrounded by short serrae; distal part appears spoon-shaped.

Etymology. The species is named after the surgeon on HMS Herald who collected the type specimen.

Remarks. Balss (1938: 74) reported a male (12.0 × 9.0 mm) from Namuka, Viti Levu, Fiji, without figures or comments. The present specimen from Fiji is relatively larger. They are presumed to be conspecific in view of their provenance. The specimen was originally died ( Fig. 4 A) but was rehydrated so the abdomen and gonopods could be studied.

The carapace form of N. rayneri n. sp. is superficially similar to N. latus although it is proportionately broader in the new species (width to length ratio 1.60 vs. 1.40). Notonyx rayneri n. sp. can also be separated from N. latus by its relatively more slender male abdomen ( Fig. 5 B) (cf. Ng & Clark 2008: fig. 2E), the G1 is sinuous in shape with the distal part blunt and subtruncate ( Fig. 6 A–D) (G1 almost straight with the distal part prominently extended and curved in N. latus, Ng & Clark 2008 : fig. 3), and the distal part of the flagellum is gently curved ( Fig. 6 E, F) (G2 tip is bent back on itself to form S-shaped structure in N. latus, Ng & Clark 2008 : fig. 4).

The G1 structure of N. rayneri n. sp. most closely resembles that of N. kumi but the two species differ in several features. The carapace of N. rayneri n. sp. is relatively broader (width to length ratio 1.60 vs. 1.4), the male telson is relatively broader with gently concave margins ( Fig. 5 B) (male telson relatively more acute in N. kumi with almost straight lateral margins, Naruse & Maenosono 2009: fig. 2a), there is a prominent spurlike projection on the outer lower margin of the G1 ( Fig. 6 A, B) (margin almost entire in N. kumi, Naruse & Maenosono 2009 : fig. 2b, c), the tip of the G1 is not projected beyond the swollen subdistal part ( Fig. 6 A–D) (distal part of G1 extends beyond the swollen subdistal part in N. kumi, Naruse & Maenosono 2009 : fig. 2b, c).

Compared to N. sagittifer n. sp., the carapace of N. rayneri n. sp. is relatively broader (width to length ratio at 1.60 vs. 1.36), the chelae are proportionately stouter ( Fig. 4 D, E vs. Fig. 1 C), and the G1 is relatively stouter, more sinuous, with the distal part not projecting beyond the swollen subdistal part ( Fig. 6 A, B) (G1 relatively longer, curved outwards with the distal part prominently elongated in N. sagittifer n. sp., Fig. 3 A, B). Although near the type locality of N. rayneri n. sp. is closest to N. nitidus ( New Caledonia), their carapace proportions, structures of the third maxillipeds, male abdomens and G1s are completely different (see Clark & Ng 2006).

Figures

FIGURE 1. Notonyx sagittifer n. sp., holotype 3 (NMCR 1522), South Lagoon, Sitankai, Mindanao, Philippines. A, dorsal view of carapace; B, frontal view of carapace; C, outer view of left chela.

FIGURE 3. Notonyx sagittifer n. sp., holotype 3 (NMCR 1522), South Lagoon, Sitankai, Mindanao, Philippines. A, entire right G 1 (dorsal view); B, entire right G 1 (ventral view); C, distal part of right G 1 (dorsal view); D, distal part of right G 1 (ventral view); E, right G 2 (ventral view); F, right G 2 (dorsal view); G, tip of right G 2 (ventral view); H, tip of right G 2 (dorsal view); I, medial spinulation of right G 2 (ventral view).

FIGURE 4. Notonynx rayneri n. sp., holotype 3 (NHM 1858.172), Vanua Levu, Nandi, Fiji. A, overall view (dried); B, dorsal view of carapace; C, frontal view of carapace; D, outer view of right chela; E, outer view of left chela.

FIGURE 5. Notonynx rayneri n. sp., holotype 3 (NHM 1858.172), Vanua Levu, Nandi, Fiji. A, left third maxilliped; B, abdomen (telson and somites 2 - 6).

FIGURE 6. Notonynx rayneri n. sp., holotype 3 (NHM 1858.172), Vanua Levu, Nandi, Fiji. A, entire right G 1 (ventral view); B, entire right G 1 (dorsal view); C, distal part of right G 1 (ventral view); D, distal part of right G 1 (dorsal view); E, right G 2 (ventral view); F, right G 2 (dorsal view); G, tip of right G 2 (ventral view); H, tip of right G 2 (ventral view); I, medial spinulation of right G 2 (dorsal view).