Indochinamon dangi, Naruse, Tohru, Quynh, Nguyen Xuan & Yeo, Darren C. J., 2011

Naruse, Tohru, Quynh, Nguyen Xuan & Yeo, Darren C. J., 2011, Three new species of Indochinamon Yeo & Ng, 2007 (Crustacea: Brachyura: Potamoidea: Potamidae) from Vietnam, with a redescription of Ranguna (Ranguna) kimboiensis Dang, 1975, Zootaxa 2732, pp. 33-48 : 44-47

Indochinamon dangi n. sp.

( Figs. 6 c, d, 9d–f, 10, 11)

Material examined. Holotype: male (60.3 by 46.9 mm) ( ZMHU), Upstream and water fall of Muong Phang stream, Muong Phang, Dien Bien Prov., 21˚27.000'N 103˚10.548'E, 1070m asl, coll. D. C. J. Yeo & A. D. Tran, 28 Jul. 2004.

Paratypes: 1 male (44.5 by 34.2 mm), 1 female (46.4 by 34.6 mm) ( ZMHU), 4 males (29.6 by 23.0 – 48.4 by 37.6 mm), 2 females (45.2 by 33.9, 36.7 by 28.1 mm) ( ZRC 2010.0175), same data as holotype; 2 males (41.9 by 32.3, 37.7 by 29.3 mm), 2 females (34.6 by 27.0, 24.0 by 19.1 mm) ( ZMHU), 4 males (26.7 by 20.7 – 41.8 by 32.2 mm), 1 female (46.7 by 35.5 mm) ( ZRC 2010.0176), Muong Phang stream, Muong Phang, Dien Bien Prov., 21˚27.159'N 103˚09.921'E, 976m asl, coll. D. C. J. Yeo & A. D. Tran, 26 Jul. 2004.

Diagnosis. Carapace ( Fig. 10 a) oval, CW 1.26–1.32 times (mean 1.30, n = 10) CL, dorsal surface ( Fig. 11 a) flat, regions well defined; epigastric, postfrontal cristae distinct, oblique, postorbital crista separated from epigastric crista, externally terminated by cervical groove, anterolateral region scattered with oblique granules. Frontal to orbital margins cristate, infraorbital margin lined with small, rounded granules, infraorbital margin ( Fig. 11 a) interrupted just below external orbital angle; suborbital region smooth, without granules; subhepatic region covered with short rows of low granules. External orbital angle at right angle, slightly directed inwards, outer margin length about one and a half times inner margin, outer margin cristate, epibranchial tooth disconnected from outer margin of external orbital angle by short gap of crista, short, not clearly larger than following granules; anterolateral margin moderately convex laterally, cristate, regularly lined with low, similar-sized granules, posterolateral margins convergent posteriorly. Posterior margin of epistome with one long lobe ( Fig. 11 a).

Ischium of third maxilliped broadly rectangular exopod flagellum longer than half width of merus.

Male cheliped carpus with rugose outer surface, inner angle with sharp, long tooth, followed vento-proximally by one small tooth; male chela ( Fig. 11 b) with swollen palm, rugose; fingers as long as palm, straight, slightly hook-shaped distally, cutting edge regularly lined with teeth, without gape when closed.

Male abdomen tongue-shaped, first segment with longitudinal ridge on middle; third segment widest; sixth segment shorter than telson, telson longer than width, lateral margin concave.

G1 ( Figs. 9 d, e) with distal fifth bent outwards at about 90°; subterminal segment with wide convexity on proximal two-fifths of outer margin, distal part of outer margin weakly concave, connected dorsally to shallow transverse slope; distal segment relatively stout, tip abruptly narrowed in dorsal view, outwards in anterior view, groove for G2 on extensor (anterior) surface, elongated opening on flexor (posterior) surface, dorsal flap absent. G2 ( Fig. 9 f) longer than G1, flagellum curving outwards, J-shaped.

Live colouration. The dorsal carapace, anteriorly to the upper half of the third maxillipeds (from the palp to the upper part of the ischium) and anterolaterally to the suborbital, pterygostomial, subhepatic, and subbranchial regions, as well as the chelipeds, and walking legs, are mostly dark brownish-grey. The anterolateral margins show some traces of orange colour. The margins of the external orbital angle and orbital, the frontal margin, and the posterior margin of the epistome are orange in colour. The distal part of the fingers of the chelae are bright orange with white tips, the orange colour spreading to the lower half and cutting edge of the movable finger and to most of the fixed finger ( Fig. 6 c, d).

Habitat and distribution. The species was collected from a small (about 1m wide), shallow stream in a secondary forest area near a rice field, with slow flowing water over, sandy and rocky substratum in the Dien Bien Province (north-western Vietnam).

Etymology. The new species is named after Professor Dang Ngoc Thanh ( Vietnam National Centre for Natural Science and Technology) for his significant contributions to the study of freshwater biodiversity and carcinology in Vietnam.

Remarks. Indochinamon dangi n. sp. is morphologically similar to I. lipkei (Ng & Naiyanetr, 1993) [type locality: Chiang Khong District, Chiang Rai Province, northwestern Thailand], especially in its strongly bent G1. However I. dangi n. sp. can be distinguished from I. lipkei by the oblique epigastric and postfrontal cristae (vs. straight), almost obliquely straight infraorbital margin (vs. ventrally convex infraorbital margin), distally narrowed telson (vs. moderately narrowed), almost perpendicularly bent distal segment with abruptly narrowed tip (vs. less bent terminal segment with gradually tapered tip) ( Figs. 9 d, e, 10a, 11a; Ng & Naiyanetr, 1993: Figs. 12A, B, 47B– E).

Figures

FIGURE 6. Live colourations of Indochinamon species. a, b, I. phongnha n. sp.; c, d, I. dangi n. sp.; e, f, I. bavi n. sp.

FIGURE 9. Male G 1 and G 2 of Indochinamon phongnha n. sp., and I. dangi n. sp. a, d, right G 1, ventral view; b, e, right G 1, dorsal view; c, f, right G 2, ventral view. a – c, I. phongnha n. sp., holotype (ZMHU, male, CL 51.9 mm, CW 68.6 mm); d – f, I. dangi, holotype (ZMHU, male, CL 46.9 mm, CW 60.3 mm). Scales = 5 mm.

FIGURE 10. Indochinamon dangi n. sp. Holotype (ZMHU, male, CL 46.9 mm, CW 60.3 mm). a, dorsal view; b, ventral view.

FIGURE 11. Indochinamon dangi n. sp. Holotype (ZMHU, male, CL 46.9 mm, CW 60.3 mm). a, frontal view; b, major chela.