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Key to species of Borneosa 1a. Anterolateral margin with the epibranchial tooth distinct, sharp, separated from rest of anterolateral margin by clear cleft (e.g., Figs. 10B, 11F, H); male sternoplenonal cavity separated from suture between thoracic sternites 2 and 3 by narrow gap, less than combined length of thoracic sternites 1 and 2 (e.g., Fig. 18B).. 2 1b. Anterolateral margin with the epibranchial tooth low to almost absent, cleft when visible, low, shallow, anterolateral margin may appear entire (e.g., Fig. 2B); male sternoplenonal cavity separated from suture between thoracic sternites 2 and 3 by relatively wide gap, more than combined length of thoracic sternites 1 and 2 (e.g., Fig. 3B)....................................................................................... 4 © 2022 Academia Sinica, Taiwan 2a. Outer margin of exorbital tooth distinctly serrated (Fig. 17B); Bulungan, Kalimantan Utara........................... B. serrata sp. nov. 2b. Outer margin of exorbital tooth entire or almost so (e.g., Fig. 8B); Sarawak...................................................................................... 3 3a. Epibranchial tooth low, separated from anterolateral margin by small cleft (Fig. 8B); third maxilliped ischium subquadrate (Fig. 9A); G1 terminal segment relatively slender, long (Fig. 21A–C); Niah, Sarawak..................................................... B. niah sp. nov. 3b. Epibranchial tooth strong, separated from anterolateral margin by prominent U-shaped cleft (Figs. 10B, 11F, H); third maxilliped ischium subrectangular (Fig. 11A); G1 terminal segment relatively stout, short (Fig. 21E–G); Bario Highlands, Sarawak............................................................................... B. bario sp. nov. 4a. P3 dactylus distinctly more slender and elongate compared to P4 dactylus (e.g., Fig. 5H, I)............................................................ 5 4b. P3 and P4 dactyli not elongate, subequal in length (e.g., Fig. 7F, G)................................................................................................ 6 5a. Frontal median triangle with dorsal margin separated from lateral margins by small gap (Fig. 2C–F); G1 terminal segment relatively short, subcylindrical (Fig. 20F, G, J, K); Gunong Mulu National Park, Sarawak................. B. tenebrosa (Holthuis, 1979) 5b. Frontal median triangle with dorsal margin contiguous with lateral margins (Fig. 4C–E); G1 terminal segment very long, cylindrical (Fig. 20M–O); Brunei and northern Sabah................................................................... B. aspera (Ng & Stuebing, 1989) 6a. Striae on lateral parts of dorsal surface of carapace relatively lower, rounded (Figs. 6B, 7I); median lobe of posterior margin of epistome acutely triangular (Fig. 6C–E).................................................... Barito, Kalimantan Tengah B. brachyphallus (Ng, 2015) 6b. Striae on lateral parts of dorsal surface of carapace strong, sharp (Fig. 15B); median lobe of posterior margin of epistome obtusely triangular (e.g., Fig. 15C–E)...................................................... 7 7a. Epibranchial tooth small but usually visible, and even when low, demarcated from the anterolateral margin by a shallow cleft (Figs. 12B, 14); G1 terminal segment with median part less distinctly bent, distal part more elongate with more tapering tip, opening small (Fig. 22A–C, E–G); Kapit area and upper Rejang, Sarawak............................................................................. B. kapit sp. nov. 7b. Epibranchial tooth not visible or very low, with the anterolateral margin appearing entire (Fig. 15B); G1 terminal segment with median part distinctly bent, distal part ending in rounded tip with wide opening (Fig. 22I–K); Batang Ai National Park and Lanjak-Entimau Wildlife Sanctuary, Kanowit Basin, Sarawak................................................................................. B. sarawakensis sp. nov. |
