Tiwaripotamon vixuyenense Shih & Do, 2014, sp. nov.
Creators: name: Shih, Hsi-Te
name: Do, Van Tu
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamidae
Tiwaripotamon
Tiwaripotamon vixuyenense

description: Tiwaripotamon vixuyenense sp. nov.
(Figs. 2–5)
Material examined. Holotype: male (26.4 × 20.5 mm) (IEBR-FC TVx01), Tung Ba Commune, Vi Xuyen District, Ha Giang Province, Vietnam, 758 m, coll. N. L. Doan & X. N. Nguyen, 2 July 2013. Paratypes: 1 male (20.7 × 16.9 mm), 1 female (21.7× 16.6 mm) (IEBR-FC TVx02), same data as holotype; 1 male (20.5× 16.2 mm), 2 females (24.1× 18.9 mm, 14.6× 11.6 mm) (NCHUZOOL 13611), same data as holotype.
Comparative material. Tiwaripotamon xiurenense Dai & Naiyanetr, 1994: 1 male (39.6× 29.7 mm) (NCHUZOOL 13610), Lipu, Guangxi Province, China, coll. local collector, 18 May 2009.
Diagnosis. Carapace about 1.3 times broader than long. Epigastric cristae distinct; postorbital cristae rounded, confluent with epibranchial tooth. External orbital angle triangular, outer margin gently convex; epibranchial tooth small, broadly triangular, separated from external orbital angle by distinct narrowly triangular cleft. Ambulatory legs conspicuously long, slender; length of fouth ambulatory merus about 6.5 times width for larger specimens, 5.9 times for smaller ones. G1 short, stout, straight; terminal segment straight, about 0.3 times length of subterminal segment.
Description. Small size in comparison with congeners (maximum CW about 25 mm). Carapace (Figs. 2A, 4 A) about 1.3 times broader than long (n = 6). Epigastric cristae rugose, distinct, separated by narrow, shallow groove that opens up into inverted V-shape posteriorly; postorbital cristae rugose, rounded, confluent with epibranchial tooth; regions behind epigastric and postorbital cristae weakly rugose. External orbital angle triangular, outer margin gently convex; epibranchial tooth small, not prominent, broadly triangular, separated from external orbital angle by distinct narrowly triangular cleft; anterolateral margin convex, serrated in upper part; metabranchial regions smooth.
Ischium of third maxilliped (Fig. 2C –E) quadrate, about 1.3–1.5 times longer than broad, with shallow longitudinal median sulcus; exopod with short but distinct flagellum, about 1/3 of merus width (holotype without flagellum).
Chelipeds subequal, right cheliped large; outer surface smooth. Right cheliped with length of palm+pollex about 2.3 times palm height. Ambulatory legs smooth, conspicuously long, slender; length of fouth merus about 6.5 times width for larger specimens (CW> 24 mm, n = 2), 5.9 times for smaller ones (CW <22 mm, n = 4).
Male abdomen (Figs. 2B, 4 C) broadly triangular, with proximal width of 6th segment about 2.4 times length; telson broadly triangular, tip rounded, with proximal width about 1.6 times length.
Suture between thoracic sternites 2 and 3 complete, distinct (Fig. 5 A, B); thoracic sternites 5 and 6 interrupted medially; sternites 7 and 8 medially separated by distinct longitudinal median suture (Fig. 5 A, B). Male abdominal cavity reaching suture between thoracic sternites 3 and 4. Tubercles of male abdominal-locking mechanism (arrows in Fig. 5 A) positioned in thoracic sternite 5.
G1 (Fig. 3 A–H) conspicuously short, stout, straight; terminal segment straight, about 0.3 times length of subterminal segment, about 1.75 times longer than proximal width, with distal opening subventral in position. G2 (Fig. 3 I, J) about 1.1 times longer than G1, distal segment well developed, about 0.6 times longer than basal segment. Female gonopore (Fig. 5 B) in thoracic sternite 6, ovate, without operculum, opened posterio-mesially; anterio-external margin partially covered by raised rim; posterio-mesial margin surrounded by a low raised rim.
Etymology. The species is named for the type locality, Vi Xuyen, in northern Vietnam.
Coloration. Carapace and legs reddish brown, fingers and palm of chela with lighter color (Figs. 4 A–C, 5C, D).
Ecological notes. This species inhabits limestone mountains, occurring inside and outside the caves. Specimens were also found crawling on leaves and twigs about one meter above the ground at night.
Remarks. This new species can be separated from congener by the relatively small epibranchial tooth, more slender ambulatory legs and proportionately stouter G1. The epibranchial tooth of this species is small and not prominent (Figs. 2A, 4 A, 5C) and is closer to the condition in T. vietnamicum, although the epibranchial tooth of the latter is relatively much weaker and sometimes even absent (Fig. 6 A, C, D). The merus of the fouth leg is about 6.5 times longer than broad for large specimens, which is relatively more slender than those of congeners: 5.1 times for T. vietnamicum, 5.6 times for large T. edostilus specimens (see Remarks for each species below) and 5.3 times for T. xiurenense (unpublished data). The relative stoutness of G1 of this species (Fig. 3 A–H) is diagnostic, not observed in other known species.
Tiwaripotamon vietnamicum (Dang & Ho, 2002) (Fig. 6)
Geothelphusa vietnamica Dang & Ho, 2002: 4, pl. 2, fig. 2.
Tiwaripotamon vietnamicum — Yeo & Naruse 2007: 1144.— Shih et al. 2008: 37.— Dang & Ho 2012: 216, fig. 78. Hainanpotamon vietnamicum —Ng et al. 2008: 162.
Material examined. 2 males (44.5× 32.8 mm, 41.3× 31.2 mm), 1 female (47.9× 35.8 mm) (IEBR-FC TVn01); 2 males (49.6× 36.7 mm, 49.0× 36.1 mm), 1 female (47.4× 35.2 mm) (NCHUZOOL 13612); Cuc Phuong National Park, Ninh Binh Province, Vietnam, 500 m, coll. V. T. Do, 14 May 2013.
Coloration. Carapace and legs dark brown, fingers and palm of chela light brown (Fig. 6 A–D).
Ecological notes. There are no large caves in Cuc Phuong National Park (Fig. 6 E, F). This species was found living in rock crevices and holes, but wandered further from these habitats at night.
Remarks. Tiwaripotamon vietnamicum was originally described as Geothelphusa vietnamica Dang & Ho, 2002. Ng et al. (2008) provisionally referred the species to Hainanpotamon Dai, 1975, but in a revision of the genus, Yeo & Naruse (2007) transferred it to Tiwaripotamon. We agree and our genetic data supports its inclusion in Tiwaripotamon (Fig. 8).
The carapace of T. vietnamicum is about 1.3 times broader than long (n = 6). The ambulatory legs are smooth, conspicuously long and slender, and the merus of the fouth pair is about 5.1 times longer than wide (n = 5).
description: Published as part of Shih, Hsi-Te & Do, Van Tu, 2014, A new species of Tiwaripotamon Bott, 1970, from northern Vietnam, with notes on T. vietnamicum (Dang & Ho, 2002) and T. edostilus Ng & Yeo, 2001 (Crustacea, Brachyura, Potamidae) in Zootaxa 3764 (1), DOI: 10.11646/zootaxa.3764.1.2, http://zenodo.org/record/225414