Notonyx latus, Ng, Peter K. L. & Clark, Paul F., 2008

Ng, Peter K. L. & Clark, Paul F., 2008, A new species of Notonyx A. Milne-Edwards, 1873 (Crustacea: Decapoda: Brachyura: Goneplacidae) from Indonesia, Zootaxa 1897, pp. 20-26 : 21-26

publication ID	https://doi.org/ 10.5281/zenodo.184459
DOI	https://doi.org/10.5281/zenodo.6234439
persistent identifier	https://treatment.plazi.org/id/3372AD7B-DC53-BD0A-F5B3-FE65FB42FED8
treatment provided by	Plazi
scientific name	Notonyx latus
status	sp. nov.

Treatment

Notonyx latus View in CoL n. sp.

Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3

Notonyx nitidus View in CoL — Stephensen 1946: 172, Fig. 47A, B (in part, see Naruse & Maenosono in press).

Material examined. Holotype: ɗ (10.0 × 7.0 mm), stn 11, off Toeal (= Joeal), Kei Islands, Lesser Sunda Islands, Indonesia, 20 m, coll. Th. Mortensen, Danske Kei Expedition, 9 April 1922, det. T. Odhner as Notonyx nitidus, 1924 ( ZMUC). Paratype: 1 juv. ɗ (3.7 × 2.8 mm), stn 19, off Toeal (= Joeal), Kei Islands, Lesser Sunda Islands, Indonesia, 20 m, coll. Th. Mortensen, Danske Kei Expedition, 14 April 1922, det. T. Odhner as Notonyx nitidus 1924 ( ZMUC).

Diagnosis. Holotype: carapace transversely subrectangular, about 1.4 × wider than long ( Figs. 1 View FIGURE 1 A, 2A), frontal margin gently convex, about one-third carapace width ( Figs. 1 View FIGURE 1 A, 2A). Anterolateral margin short, entire, curved, unarmed; posterolateral margin gently concave, slightly diverging posteriorly ( Figs. 1 View FIGURE 1 A, 2A). Dorsal surface of carapace smooth, without indication of regions except for shallow impression in gastro-cardiac area; dorsal surface gently convex anteriorly, posteriorly ( Figs. 1 View FIGURE 1 A, 2A). Cornea pigmented, small ( Fig. 2 View FIGURE 2 A). Small gape present between third maxillipeds when closed; merus quadrate, slightly shorter than ischium; anteroexternal angle of merus forming right angle ( Fig. 2 View FIGURE 2 B). Chelipeds subequal ( Fig. 1 View FIGURE 1 A, C), outer surfaces smooth, with distinct keel on ventral margin extending almost to tip of finger ( Fig. 1 View FIGURE 1 C); dorsal margin of propodus smooth, unarmed; inner margin of carpus rounded, with low spine, inner margin finely denticulate ( Figs. 1 View FIGURE 1 A, 2C). Walking legs relatively long, surfaces smooth, margins lined with numerous short, long setae ( Figs. 1 View FIGURE 1 A, B, 2D). Thoracic sternum relatively broad; surface lightly but distinctly pitted; sternites 1, 2 completely fused, separated from sternite 3 by distinct transverse suture; sternites 3, 4 fused except for lateral parts of sutures ( Fig. 1 View FIGURE 1 B). Male abdomen relatively broad, third somite broadest; telson rectangular, lateral margins gently sinuous ( Figs. 1 View FIGURE 1 B, 2E). G1 relatively slender, almost straight for most of length, subdistal part slightly dilated with numerous small spines, distal part elongated to form hook-like projection with subtruncate tip ( Fig. 3 View FIGURE 3 A–D). G2 much longer than G1, distal segment longer than basal segment ( Fig. 4 View FIGURE 4 A); junction between distal and subdistal segments marked by concave area surrounded by short serrae ( Fig. 4 View FIGURE 4 B); tip of distal segment abruptly tapering, S-shaped, directed upwards to form sharp hook ( Fig. 4 View FIGURE 4 C).

Etymology. The name is derived from latus, Latin for “broad,” for the relatively broad carapace.

Remarks. Clark & Ng (2005) redescribed and figured N. nitidus A. Milne-Edwards, 1873 , in detail on the basis of the holotype and a good series of specimens from the type locality, New Caledonia, as well as from Chesterfield Islands, New Guinea and Timor Sea. They commented that specimens identified as “ N. nitidus ” by Tesch (1918), Stephensen (1946) and Serène & Umali (1972) were in fact new. In 2006 the authors of the present study examined Tesch’s (1918) and Stephensen’s (1946) material lodged in the Rijksmuseum van Natuurlijke Historie, Leiden, and ZMUC, and came to the conclusion they represented two distinct species, with different carapace and G1 structures. Both species are found in Indonesia. In the intervening period, Naruse & Maenosono (in press) discovered a new species from Japan. It was discovered that one of the Indonesian species was in fact conspecific with the new Japanese species being described by Naruse & Maenosono (in press). They have included the Indonesian specimens in their paper. The other species listed by Stephensen (1946) as N. nitidus is here described as N. latus n. sp.

Compared to known congeners, N. latus n. sp. is closest to N. gigacarcinicus Clark & Ng, 2005 , in the broad carapace proportions and form of the third maxillipeds, but can be separated by the relatively longer walking legs ( Figs. 1 View FIGURE 1 A, B, 2D) than in N. gigacarcinicus (see Clark & Ng 2005: Figs. 4 View FIGURE 4 A, B, 5G), the presence of a low spine on the inner margin of the cheliped carpus, with the inner margin weakly denticulate ( Fig. 2 View FIGURE 2 C) (unarmed and the margin smooth; Clark & Ng 2005: Fig. 5E, F), male abdomen ( Fig. 2 View FIGURE 2 E) relatively broader than in N. gigacarcinicus (see Clark & Ng 2005: Fig. 5H), the G1 being prominently more slender, the subdistal part without a prominent swelling and the distal part elongated into a hook-like structure ( Fig. 3 View FIGURE 3 ) (thicker, with a prominent swelling and the distal part short and not elongated in N. gigacarcinicus ; Clark & Ng 2005: Fig. 5J, K), and the G2 with the tip S-shaped and directed upwards ( Fig. 4 View FIGURE 4 ) (simple hooked tip in N. gigacarcinicus ; Clark & Ng 2005: Fig. 5I). The shape of the cheliped carpus of N. latus n. sp. is similar to that of N. nitidus ( Fig. 2 View FIGURE 2 C; Clark & Ng 2005: Fig. 5C), but the two species differ markedly in the form of their carapace proportions and the structure of the third maxilliped, which has the ischium as long as broad in the new species ( Fig. 2 View FIGURE 2 B) but the ischium is distinctly longer than broad in N. nitidus ( Clark & Ng 2005: Fig. 3 View FIGURE 3 B).

Clark & Ng (2005) discussed whether the Indonesian and Philippines specimens of Stephensen (1946) and Serène & Umali (1972) are conspecific. Compared to the Philippines specimen figured by Serène & Umali (1972, as N. nitidus ), N. latus n. sp. differs in apparently having a relatively less broad carapace ( Fig. 1 View FIGURE 1 A, 2A) than in the Philippines specimen (Serène & Umali 1972: Pl. 8 fig. 9), the ischium of the third maxilliped is relatively shorter ( Fig. 2 View FIGURE 2 B) than in the Philippines specimen (Serène & Umali 1972: Fig. 90), the male abdomen is similar in proportions in general although the telson appears to be relatively shorter ( Fig. 2 View FIGURE 2 E) than in the Philippines specimen (Serène & Umali 1972: Fig. 91), and the subdistal part of the G1 is prominently less swollen, with the distal part elongate and hooked with a subtruncate tip ( Fig. 3 View FIGURE 3 ) (subdistal part more swollen, the distal part is not elongate or hooked and the tip is bifurcated; Serène & Umali 1972: Figs. 92, 93). The Philippines specimen has lost all its walking legs so the relative proportions of the structure cannot be compared. The carpus of the cheliped was not described, but from their figure (Serène & Umali 1972: Pl. 8 figs. 9, 10), it appears to resemble that of N. latus n. sp. by having a low inner spine. Their G2 structures are also not substantially different ( Fig. 4 View FIGURE 4 ; Serène & Umali 1972: Figs. 94, 95). The male specimen reported by Serène & Umali (1972: 83) measured 7.5 × 5.0 mm (see correction in Serène & Soh 1976: 19), and is distinctly smaller than the 10.0 × 7.0 mm holotype male of N. latus n. sp. but the differences are rather substantial and suggests they are not conspecific. The Philippine specimen needs to be examined before a conclusive identification can be made.

The smaller juvenile male specimen of N. latus n. sp. from the type locality is very similar to the holotype male in its general features although its carapace appears to be relatively less broad. It is, however, not in good condition being slightly damaged so the measurements of the carapace are not accurate. Its gonopods are not developed but the relative proportions of its walking legs agree well with the holotype.