Identity of the freshwater crab Indochinamon beieri (Pretzmann, 1966), with the description of a new genus and four new species from northeastern India (Decapoda, Brachyura, Potamidae) Author Pati, Sameer K. Zoological Survey of India, Western Regional Centre, Akurdi, Pune 411 044 (India) sameer_pati@yahoo.co.in Author Mitra, Santanu Zoological Survey of India, Crustacea Section, Fire Proof Spirit Building, 27 Jawaharlal Nehru Road, Kolkata 700 016 (India) Author Ng, Peter K. L. Lee Kong Chian Natural History Museum, National University of Singapore, 2 Conservatory Drive, Singapore 117377 (Republic of Singapore) text Zoosystema 2024 2024-09-24 46 23 589 615 https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/zoosystema2024v46a23.pdf journal article 303655 10.5252/zoosystema2024v46a23 a09a56e8-aea6-4574-b583-ca084c7e3223 1638-9387 13837101 9195A8AB-6FA8-4828-B8D1-DDEC94E99A6D Capitamon mizoramense n. sp. ( Figs 15 ; 16 ; 17 ) urn:lsid:zoobank.org:act: 325C0E17-991F-43A7-9D11-48CD57D41299 Indochinamon beieri – Mitra 2017: 23 , figs 49-51; 71; 113-115 [not Potamon beieri Pretzmann, 1966 ]. TYPE MATERIAL . — Holotype . India • ♂ (46.3 × 35.7 mm ); Mizoram state : Champhai district : Zokhawthar , c. 2 km from Indo-Myanmar International Border , collected from small stream connected to Tiau River ; 23°21’53”N , 93°23’9”E ; alt. 728 m ; 23.IX.2013 ; S. Mitra leg.; ZSIK C.6122/2A . Paratypes . India • ♂ (31.4 × 24.9 mm ), ♀ (51.3 × 37.6 mm ); same data as for holotype; ZSIK C.6122/2B • 7 ♂ (largest male, 60.0 × 44.6 mm ), 4 ♀ (largest female, 52.0 × 39.6 mm ); Mizoram state : Lunglei district : Tui-pui village , collected from small stream connected to Tui-pui River ; 22°52’47”N , 92°56’9”E ; alt. 228 m ; 24.IX.2013 ; S. Mitra leg.; ZSIK C.6131/2 • 5 ♂ (largest male, 37.5 × 29.2 mm ), 4 ♀ (largest female, 37.7 × 28.8 mm ); Mizoram state : Serchhip district : near Vantawng waterfalls, about 9 km from Thenzawl market, collected from small water channel; 23°14’2”N , 92°45’3”E ; alt. 720 m ; 26.IX.2013 ; S. Mitra leg.; ZSIK C.6125/2 . DIAGNOSIS. — Carapace ovate, broader than long (CW/CL = 1.3), relatively low ( CH /CW = 0.4); epigastric cristae well-developed, rugose; postorbital cristae well-developed, relatively sharp, oblique in dorsal view; external orbital angle triangular, with short outer margin, c. 2 × inner margin; epibranchial tooth low, blunt, positioned above level of postorbital cristae; cervical grooves discontinuous, not reaching to level of postorbital cristae; epistome posterior margin with well-developed, triangular median tooth, outer parts sloping downwards ( Fig. 15A, B ). Third maxilliped exopod with short flagellum, shorter than width of merus ( Fig. 16B ). Chelipeds rugose, unequal, inner distal tooth on carpus relatively narrow ( Figs 15A, C ; 16C ). Male s3/ s4 indiscernible except for two short lateral clefts ( Figs 15C ; 16D ). Male pleonal somite 6 relatively broader (proximal width c. 2.1 × medial length), equal in length to pleonal somite 5, with gently convex lateral margins ( Figs 15C ; 16E ). Male telson relatively broader (proximal width c. 1.3 × medial length), with concave lateral margins ( Figs 15C ; 16E ). G1 ultimate article relatively more strongly bent at angle of about 110° from longitudinal axis, with sinuous outer margin, dorsal flap relatively high, narrowly triangular ( Figs 16F ; 17A , C-E). G2 c. 1.3 × length of G1; ultimate article long, c. 0.6 × length of penultimate article ( Figs 16F, G ; 17B, D ). Vulvae laterally partially covered by protruding sternal cover, visible in ventral view ( Fig. 16I ). FIG . 15. — Capitamon mizoramense n. gen., n. sp. , holotype ♂ (46.3 × 35.7 mm) (ZSIK C.6122/2A): A , overall dorsal view; B , frontal view of cephalothorax; C , overall ventral view. Scale bars: A, C, 20 mm; B, 10 mm. FIG . 16. — Capitamon mizoramense n. gen., n. sp. , holotype ♂ (46.3 × 35.7 mm) (ZSIK C.6122/2A) ( A -G ), paratype ♀ (51.3 × 37.6 mm) (ZSIK C.6122/2B) ( H , I ): A , mouthparts; B , right third maxilliped; C , chela (outer view); D , s1-s8 showing right G1 in situ ; E , pleon and telson; F , left G1 (dorsal view); G , left G2; H , pleonal somites 3-6 and telson; I , s1-s8 showing vulvae. Scale bars: A, B, D, E, H, I, 5 mm; C, 10 mm; F, G, 2 mm. FIG . 17. — Capitamon mizoramense n. gen., n. sp. , holotype ♂ (46.3 × 35.7 mm) (ZSIK C.6122/2A): A , left G1 ultimate article (dorsal view); B , left G2; C , left G1 ultimate article (ventral view); D , left G1 (dorsal view); E , left G1 (ventral view). Scale bar: A, C, 1 mm; B, D, E, 2 mm. ETYMOLOGY . — The specific epithet refers to Mizoram state in northeastern India , where the new species is found. COLOUR IN LIFE . — Crabs are olive green or brown, with paler ventral side and blood red joints of chelipeds (see Mitra 2017 : fig. 71). ECOLOGICAL NOTES (modified from Mitra 2017 ). — Capitamon mizoramense n. gen., n. sp. is a hill stream crab that prefers rocky habitats. This species is very common in the Champhai district of Mizoram . Local fishermen catch these crabs at night and sell them alive in the early morning for food. The population of this species may decline in the near future if these crabs are over-harvested. GEOGRAPHICAL DISTRIBUTION . — Capitamon mizoramense n. gen., n. sp. is known only from Mizoram state of northeastern India ( Fig. 1 ). REMARKS Capitamon mizoramense n. gen., n. sp. is unique among congeners due to the G1 ultimate article, which is relatively more strongly bent at an angle of about 110° from longitudinal axis of the G1, and possesses the relatively high and narrowly triangular dorsal flap ( Figs 16F ; 17A , C-E). The remaining nominal species of Capitamon n. gen. have a G1 ultimate article relatively less strongly bent at an angle of about 60-75° from longitudinal axis of the G1 ( Figs 6F ; 7D, E ; 8C ; 10A ; 11D, E ; 13F ; 14D, E ; see Pati et al. 2020 : figs 4a, d; 5a, c). Capitamon mizoramense n. gen., n. sp. shares the following features of the G1 with C. meitei n. gen., n. sp. : sinuous outer margin of the G1 ultimate article and the relatively high, narrowly triangular dorsal flap on the G1 ultimate article ( Figs 13F ; 14A , C-E; 16F; 17A, C-E). Other features of G1 and vulvae, however, distinguish them (see Remarks for C. meitei n. gen., n. sp. ).