Geosesarma pylaemenes, Ng, Peter K. L., 2015

Ng, Peter K. L., 2015, Semiterrestrial crabs of the genus Geosesarma De Man, 1892 (Crustacea, Brachyura, Sesarmidae) from western Borneo, Indonesia, with descriptions of three new species, Zootaxa 4048 (1), pp. 37-56 : 41-43

Geosesarma pylaemenes sp. nov.

( Figs. 3 , 4 )

Material examined. Holotype: male (11.6 × 10.6 mm) ( MZB Cru 4394), in ricefields near Anjungan, Kalimantan Barat, coll. H.H. Tan & Y.Y. Goh, 29 April 1998. Paratypes: 8 males (5.3 × 4.8 mm – 11.0 × 10.0 mm), 6 females (6.7 × 6.1 mm – 10.6 × 9.5 mm), 4 ovigerous females (8.8 × 7.9 mm – 10.3 × 9.2 mm) ( ZRC 2015.0459), 4 males, 4 females ( MZB Cru 4395), ricefields near Anjungan, Kalimantan Barat, coll. H.H. Tan & Y.Y.Goh, 29 April 1998.

Diagnosis. Carapace subtrapezoidal, wider than long, width to length ratio 1.09–1.12, lateral margins gently diverging ( Figs. 3 A, B); dorsal surface with visible regions, anterior regions mostly smooth except small rounded granules on epigastric regions ( Fig. 3 A–C); front deflexed, frontal lobes broad with gently convex margins; postfrontal, postorbital cristae low but distinct ( Fig. 3 B, C); external orbital tooth broadly triangular, directed obliquely, outer margin gently convex, tip not extending beyond lateral margin ( Figs. 3 A, B). Merus of third maxilliped subovate, subequal in length to ischium; exopod slender with long flagellum ( Fig. 4 A). Outer surface of palm of adult male covered with small rounded granules; inner surface with prominent transverse comb-like ridge; dorsal margin of dactylus with 8–10 low tubercles on proximal two-thirds ( Figs. 3 D–F). Ambulatory legs with relatively slender merus, with sharp subdistal spine on dorsal margin, surfaces gently rugose ( Figs. 3 A, 4C). Male abdomen triangular; somite 6 very wide, with strongly convex lateral margins; telson semicircular, partially recessed into distal margin of somite 6 ( Figs. 4 B). G1 slender, distal pectinated part elongated, gently curved, spatuliform, tip not medially clefted ( Fig. 4 D–G).

Etymology. Pylaemenes was the husband of Amphinome in Greek mythology. The name alludes to the similarity of the species with G. amphinome . The name is used as a noun in apposition.

Colour. Not known.

Remarks. Of interest is that two specimens of G. pontianak sp. nov. were found among the material of G. pylaemenes sp. nov. collected. The latter species is usually associated with closed forests and these may have inadvertently wandered out into the adjacent open areas.

See remarks for G. amphinome .

Figures

FIGURE 3. Geosesarma pylaemenes sp. nov., holotype male (11.6 × 10.6 mm) (MZB Cru 4394), Anjungan, Kalimantan Barat, Borneo. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, dorsal view of right chela; E, outer view of right chela; F, inner view of right chela.

FIGURE 4. Geosesarma pylaemenes sp. nov., holotype male (11.6 × 10.6 mm) (MZB Cru 4394), Anjungan, Kalimantan Barat, Borneo. A, left third maxilliped; B, male abdominal somites 1 – 6 and telson; C, right last second ambulatory leg; D, left G 1 (dorsal view); E, distal part of left G 1 (dorsal view); F, left G 1 (subventral view); G, left G 1 (ventral view). All structures denuded. Scales: A – C = 1.0 mm; D – G = 0.5 mm.