A new species of the genus Arachnothelphusa Ng, 1991 (Crustacea: Decapoda: Gecarcinucidae) from a limestone cave in Sarawak (Malaysian Borneo) Author Grinang, Jongkar Author Ng, Peter K. L. text Raffles Bulletin of Zoology 2021 2021-01-12 69 1 7 journal article 10.26107/RBZ-2021-0001 2345-7600 5351566 F861B9E5-475A-4A3D-B2AC-B49646FA7CC9 Key to species of Arachnothelphusa of Borneo 1. Epibranchial tooth very low or indistinct; external orbital tooth very low, broad; anterolateral region less rugose, fine granules, carapace surface smooth ( Figs. 1C, F , 2A, B, C, F, G , 4A ); G1 gently curving outwards, terminal segment about one-third length of subterminal segment; distal segment of G2 less than a quarter length of basal segment ( Fig. 3A–E )........................ ........................... A. sarang , new species (northern Sarawak ) – Epibranchial tooth distinct, triangular; external orbital tooth triangular; anterolateral region prominently rugose, coarse granules, carapace surface rugose ( Fig. 4B–E ); G1 gently or strongly curving outwards, terminal segment either half, onethird or a quarter length of subterminal segment; distal segment of G2 either a quarter or one-fifth length of basal segment ( Fig. 5 )..............................................................................................2 2. Epibranchial tooth distinct, acutely triangular; G1 strongly curving outwards ( Fig. 5F, H, O, Q )......................................3 – Epibranchial tooth distinct, relatively blunt; G1 gently curving outwards ( Fig. 5A, C, K )........................................................4 3. Epibranchial tooth acutely triangular, distinctly separated from external orbital tooth by wide, deep cleft; external orbital acutely triangular ( Fig. 4B ); terminal segment of G1 about half of length of subterminal segment; distal segment of G2 about quarter length of basal segment ( Fig. 5A–E )................. ...................................... A. merarapensis (northern Sarawak ) – Epibranchial tooth distinct but relatively small, separated from external orbital tooth by small cleft; external orbital tooth broadly triangular ( Fig. 4E ); terminal segment of G1 about one-third of length of subterminal segment; distal segment less than a quarter length of basal segment ( Fig. 5O–S )......... ......................................... A. melanippe ( central Kalimantan ) 4. Epibranchial tooth distinct; external orbital tooth broadly triangular ( Fig. 4D ); terminal segment of G1 about a third length of subterminal segment ( Fig. 5K–M )............................ ............................................ A. kadamaiana (northern Sabah ) – Epibranchial tooth distinct; external orbital tooth triangular; terminal segment of G1 about a quarter length of subterminal segment....................................................................................5 5. Epibranchial tooth distinct on both sides, separated from external orbital tooth by deep, broad U-shaped cleft; external orbital tooth triangular ( Fig. 4C ); G1 with cone-shaped terminal segment, about a quarter length of subterminal; distal segment of G2 less than fifth length of basal segment ( Fig. 5F–J )....... ..................................................... A. terrapes (eastern Sabah ) – Epibranchial tooth distinct on both sides, small, blunt, not separated from external orbital tooth by cleft.......................... .......................................... A. rhadamanthysi (eastern Sabah )