Metadynomene tuamotu Ng & Mclay, 2010, sp. nov.
Creators: name: Ng, Peter K. L.
name: Mclay, Colin L
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Dynomenidae
Metadynomene
Metadynomene tuamotu

description: Metadynomene tuamotu sp. nov.
(Figs. 1A; 2A, C, E; 3A, C; 4A)
Metadynomene tanensis — McLay 1999: 521 (part) (not Dynomene tanensis Yokoya, 1933).
Material examined. Holotype male (29.1 × 27.6 mm) (MNHN-B26566), Fangatafu, Tuamotu Archipelago, French Polynesia, station 487, 22°14.1'S 138°47.2'W, 310 m, coll. J. Poupin, 25 April 1995.
Diagnosis. Carapace width slightly greater than length; dorsal, lateral surfaces densely, uniformly covered with short, soft setae outlining regions, grooves on carapace, actual surface being almost completely obscured; suborbital margin shelf-like, projecting, visible from dorsal view; anterolateral margin with 4 low but distinct teeth (including external orbital tooth) before end of branchial groove; start of posterolateral margin (after end of branchial groove) with small low tubercle; cheliped carpus with prominent lobe on outer margin; cheliped dactylus gently curved with subspatuliform distal part; inferior margin of P2–P4 with less than 5 spines; merus, carpus of P2–P4 subfoliaceous with distinct cristae dorsal margin separated from rest of article by prominent longitudinal groove; male telson subtriangular.
Etymology. The species is named after its type locality, the Tuamotu Archipelago. The name is used as a noun in apposition.
Remarks. Guinot (2008: 10) noted that a suite of characters argued for the recognition of a separate subfamily, the Metadynomeninae, for Metadynomene. These include the uropod being as long as abdominal somite 6 (see also Guinot & Bouchard 1998), the presence of a small process on the coxa of P3, the basisischium of P5 not fused to the merus and the coxa of the P5 covers the penis. The present new species does not add any new characters that define the genus or sub-family.
The more ovoid carapace shape of M. tuamotu sp. nov. (Fig. 1A) is closer to M. devaneyi, with M. tanensis being more quadrate (Fig. 1 B). This is because the posterolateral margin of M. tuamotu sp. nov. is relatively longer than that of M. tanensis. Significantly, the third anterolateral tooth of M. tuamotu sp. nov. (Fig. 2A) is relatively smaller than that of M. tanensis (Fig. 1 B) even though the overall size of the type is larger. Other differences include the relatively deeper grooves and more prominent lobes on the outer margin of the carpus of the cheliped on M. tuamotu sp. nov. (Fig. 3A) (less prominent in M. tanensis, Fig. 3B), the proportionately stouter P2-P 4 in which the dorsomarginal cristae of the merus and carpus are more developed (Fig. 3C) (relatively more slender with much lower dorsal cristae in M. tanensis, Fig. 3 D) as well as the relatively more triangular male telson (Fig. 2 E) (more semicircular in M. tanensis, Fig. 2 F). Although the type male of M. tuamotu sp. nov. is larger than any known M. tanensis s. str., the suite of differences observed here suggest they are not conspecific. In addition, the kind of pubescence of the two species appears to be slightly different. In M. tuamotu sp. nov., the setae are relatively finer and the pubescence generally more velvety. In M. tanensis, the pubescence is generally of a coarser texture (Figs. 1A, 2A, C versus Figs. 1 B, 2B, D) (see Ahyong et al. 2008: 72, Figs. 43, 44). The live colours of the two species also appear to differ. Metadynomene tuamotu is generally yellowish-orange overall (Fig. 4 A) while M. tanensis is brown to orange-brown (Fig. 4 B, C). The male first gonopod of M. tuamotu sp. nov. is not diagnostically different from M. tanensis.
The four known species of Metadynomene have non-overlapping distributions: M. crosnieri McLay, 1999, is known only from the type locality, the Glorieuse Islands, south of the Seychelles, Indian Ocean; M. tanensis (Yokoya, 1933) is widespread in the Western Pacific, from Japan to New Zealand (McLay 2009); M. devaneyi (Takeda, 1977) is known from the Hawaiian and Marquesas Is., French Polynesia (McLay 1999); and M. tuamotu sp. nov. is only known from the Tuamotu Archipelago in French Polynesia, thus far. The two species from French Polynesia are recorded from island groups separated by approximately11°, the Marquesas and Tuamotus. The taxonomy of the most widespread species, M. tanensis, will also need further attention. The specimens on hand (McLay & Ng 2005; Ahyong et al. 2009; McLay 2009) show some differences in carapace form and colour, and we have doubts if these can all be explained by variation.
description: Published as part of Ng, Peter K. L. & Mclay, Colin L, 2010, Metadynomene tuamotu, a new species of dynomenid crab from French Polynesia (Crustacea: Decapoda: Brachyura), pp. 48-54 in Zootaxa 2405 on pages 48-53, DOI: 10.5281/zenodo.294087