Binhthuanomon vinhtan, Le, Van Tu Do Van Tho & Phan, Doan Dang, 2015

Le, Van Tu Do Van Tho & Phan, Doan Dang, 2015, Binhthuanomon vinhtan, a new genus and new species of semi-terrestrial freshwater crab (Crustacea: Decapoda: Brachyura: Potamidae) from south central Vietnam, Zootaxa 4052 (1), pp. 117-126 : 118-126

publication ID	https://doi.org/ 10.11646/zootaxa.4052.1.6
publication LSID	lsid:zoobank.org:pub:D445AB8A-B56C-47B3-B3F0-AC951E3DE76C
DOI	https://doi.org/10.5281/zenodo.6097107
persistent identifier	https://treatment.plazi.org/id/1468860F-FFDE-FFD2-FF3F-660931E5FD85
treatment provided by	Plazi
scientific name	Binhthuanomon vinhtan
status	sp. nov.

Treatment

Binhthuanomon vinhtan View in CoL sp. nov.

( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 6 View FIGURE 6. A – B )

Material examined. Holotype: male (53.9 × 42.9 mm) (ITB-FC PNx01), 11°22'50.5"N 108°47'49.0"E, Nui Chua, Vinh Tan commune, Tuy Phong district, Binh Thuan Province, Vietnam, 700 m, coll. Phan Doan Dang & Le Van Tho, July 2014. Paratypes: 6 male (51.3 40.0 mm, 50.5 × 40.0 mm, 47.0 × 37.0 mm, 46.0 × 37.0 mm, 41.0 × 32.0 mm, 35.0 × 28.0 mm) (ITB-FC PNx02-07), 3 female (37.0 × 29.5 mm, 34.3 25.7 mm, 23.8 18.8 mm) (ITB-FC PNx08-10), same data as holotype.

Comparative material. Villopotamon thaii Dang & Ho, 2003 : Holotype, male (54.5 × 40.2 mm) ( IEBR), stream at Ba Na (Quang Nam province), Vietnam, coll. unknown, 20 April 2002. Paratypes: 1 male (50.9 × 38.2 mm), 2 females (larger 40.6 × 35.6 mm) ( IEBR), same data as holotype. Balssipotamon ungulatum ( Dang & Ho, 2003) : Holotype, male (57.9 × 44.8 mm) ( IEBR), stream at Ninh Hai (Ninh Phuoc District, Ninh Thuan Province), Vietnam, coll. unknown, 29 September 2002. Paratypes: 1 male (52.0 × 39.4 mm), 1 female (55.0 × 41.3 mm) ( IEBR), same data as holotype. Laevimon kottelati Yeo and Ng, 2005 : male (45.4 × 31.9 mm) (IEBR-FC LKx01), 20°46'58.5"N 107°0'1.8"E, unnamed small stream near Trung Trang cave, Ca Ba island, Hai Phong, Vietnam. Hainanpotamon rubrum (Dang & Tran, 1992) : male (22.6 × 16.8 mm) (IEBR-FC HRx01), Xuan Son National Park, Phu Tho, Vietnam.

Description. Carapace distinctly transverse, about 1.26 times broader than long (n = 10), high; dorsal surface strongly inflated, swollen vertically, laterally, glabrous; regions poorly defined, cervical grooves undiscernible, Hshaped depression shallow but distinct ( Figs. 2 View FIGURE 2 A, 3A). Epigastric cristae poorly developed, rounded, smooth, confluent with postorbital cristae; postorbital cristae poorly developed, straight, rounded, smooth; regions behind epigastric, postorbital cristae smooth ( Figs. 2 View FIGURE 2 A, 3A). Frontal margin broadly emarginate medially; frontal region strongly deflected downward, smooth; antennular fossae slit-like when viewed from frontal view; orbital region very narrow, smooth; supraorbital margin very gently sinous, cristate; infraorbital margins cristate, almost straight; orbital region smooth, relatively narrow; eyes normally developed; subhepatic, subbranchial regions smooth ( Figs. View FIGURE 2

2A, B). External orbital angle low but distinct, triangular, smooth; epibranchial tooth indistinct, separated from external orbital angle by wide cleft; anterolateral margin convex, smooth; posterolateral margin rounded, not convergent posteriorly; branchial region smooth, inflated; metabranchial region almost smooth, with faint oblique striae ( Figs. 2 View FIGURE 2 A, B). Epistome anterior margin with median triangle; posterior margin with low median triangular tooth, slightly crenulated, with outer part slightly concave ( Fig. 2 View FIGURE 2 B).

Third maxilliped glabrous; ischium rectangular, about 1.67 times longer than broad, with distinct longitudinal median sulcus; merus squarish, longer than half (0.54 times) of ischium length, with concave outer surface; palp normal with tip exceeding proximal margin of merus; exopod relatively long, exceeding upper edge of ischium, exceeding proximal margin of merus, distally tapered, blunt tooth on distal part of inner margin weakly developed, with short but distinct flagellum, slightly longer than half width (0.63) of merus ( Figs. 2 View FIGURE 2 B, 3C).

Ambulatory legs normal, glabrous, relatively slender; dactyli elongated, slender; merus unarmed with upper margin weakly serrated; in second pair dactylus about 6.56 times longer than proximal width, propodus about 2.71 times longer than broad, about 0.83 times length of dactylus, carpus about 0.76 times length of dactylus, merus about 1.41 times longer than dactylus (n = 4); fourth pair with dactylus about 6.19 times longer than proximal width, propodus about 0.88 times length of dactylus, carpus about 0.81 times length of dactylus, merus about 3.04 times longer than proximal width, about 1.34 times longer than dactylus (n = 4) ( Fig. 2 View FIGURE 2 A).

Suture between anterior thoracic sternites 2, 3 complete, distinct, straight; groove between sternites 3, 4 distinct, broad, not fused with tip margin of abdominal cavity ( Fig. 2 View FIGURE 2 C); thoracic sternites 5, 6 medially interrupted; sternites 7, 8 medially separated by distinct longitudinal median suture. Male abdominal cavity reaching imaginary line joining middle points of cheliped bases (at sternite 4) ( Fig. 2 View FIGURE 2 D). Tubercles of male abdominal-locking mechanism positioned in thoracic sternite 5.

Male abdomen broadly triangular; telson narrowly triangular, broader than long, lateral margins deeply concave, tip rounded, subequal in length to sixth segment; segment 6 with proximal width about 2.29 times length, lateral margins gently convex; lateral margins of segments 4 to 5 straight; lateral margins of segment 3 gently convex ( Figs. 2 View FIGURE 2 C, 3B).

Gl sinuous, distinctly sinuous ( Fig. 2 View FIGURE 2 D); terminal segment slender, tapered, about 0.26 times length of subterminal segment, about 2.82 times longer than proximal width, without dorsal flap, sparsely covered by pubescence in ventral side, groove for accommodation of G2 marginal; subterminal segment relatively slender, sinuous, without neck-like distal part, subdistal cleft or shelf on outer margin ( Figs. 4 View FIGURE 4 A–H). G2 equal or slightly longer than G1 with distal segment shorter than half length of basal segment ( Figs. 4 View FIGURE 4 I–J).

Etymology. The new species is named after the type locality, Vinh Tan. The name is used as a noun in apposition.

Coloration. Carapace, abdomen and ambulatory legs reddish brown, chelipeds with magenta color.

Ecological notes. This species inhabits forested mountain areas ( Figs. 5A–C View FIGURE 5. A – C. A ). The crabs were found living in vertical burrows, beneath large rocks or under fallen trees, near one stream bank ( Figs. 6A, B View FIGURE 6. A – B ). Few individuals wer also found in the stream, however. It is believed that this species spends almost all of their time in terrestrial environments. Indeed, the more terrestrial habit is usually associated with freshwater crabs with a high and swollen carapace ( Yeo & Ng, 2005). The crabs are usually active in the evening until early morning. In the evening, the stream area is usually covered by fog and therefore very humid. It is very difficult to find the crabs in the dry season. The best time to collect them is during the rainy season, especially after heavy rain. The crabs feed primarily on insects and plants along streams.

Remarks. This species is found only in limited numbers in and around one small stream, 800 m in length, located in south central Vietnam. It could not be found in other regions around this area (north central and Central Highlands of Vietnam) during our surveys. We believe this species has a small distribution area. The area of occupancy is not part of any protected area and is strongly impacted by deforestation. Local people sometime catch these crabs for food; however, it is only when they accidentally collect them. Therefore, this species should be considered endangered due to limited range and impacts of deforestation on the IUCN Red List Categories and Criteria (IUCN, 2001).