Key to Javan Species

1. Dorsal margin of dactylus of male chela with 3 or 4 tubercles; G1 relatively stout...................................................................2

– Dorsal margin of dactylus of male chela with more than 5 tubercles; G1 relatively slender ..............................................3

2. Male pleon with somite 6 trapezoidal (Fig. 11D, E); G1 proportionately very stout, wide, chitinous part very short, bent about 45° along longitudinal axis (Fig. 12B–F) [Bogor Regency, West Java].......................G. robustum, (Ng & Wowor, 2019)

– Male pleon with somite 6 subrectangular (Fig. 8D, E); G1 proportionately less stout, more narrow, chitinous distal part relatively elongate, bent about 80° along longitudinal axis (Fig. 10B–D) [Sukabumi Regency, West Java]................................ ........................................................ G. sukabumi, (Ng & Wowor, 2019)

3. Dorsal margin of dactylus of male chela with 6 or 7 large tubercles (Fig. 22F–H); G1 very short, stout with short, rounded chitinous distal part (Fig. 23B–F) [Malang Regency, East Java] ................................................. G. rouxi (Serène, 1968a)

– Dorsal margin of dactylus of male chela with 7–19 small tubercles along almost entire length; G1 slender, chitinous distal part long, slender to spatulate.......................................4

4. Dorsal margin of dactylus of male chela with 7–13 small tubercles (including small one near tip) along almost entire length; species living from lowlands to about 700 m asl......5

– Dorsal margin of dactylus of male chela with 15–19 small tubercles (including small one near tip) along almost entire length; montane species, from 900 m asl and above.............9

5. Carapace in life distinctly with anterior and posterior halves differently coloured.................................................................6

– In life, carapace evenly coloured grey, brown, orange or purple, the anterior and posterior halves not distinctly separated......7

6. Anterior half of carapace purple to purplish-brown, posterior halfcream to yellowish-white (Ng et al., 2015: fig. 6A–C); dorsal margin of dactylus of male chela with 7–9 small tubercles (Ng et al., 2015: fig. 5D) [Cilacap Regency, Central Java]............ ...........................G. dennerle (Ng, Schubart & Lukhaup, 2015)

– Anterior half of carapace bright purple on anterior half, posterior half bluish-grey (Ng & Davie, 1995: 32); dorsal margin of dactylus of male chela with 10 or 11 small tubercles (Ng & Davie, 1995: fig. 2D, E; Ng et al., 2015: fig. 5C) [Ujung Kulon, Lebak Regency, Banten] ......... G. bicolor (Ng & Davie, 1995)

7. Carapace evenly orange throughout in life (Ng et al., 2015: fig. 6D–F); dorsal margin of dactylus of male chela with with 7–9 small tubercles (Ng et al., 2015: figs. 5E) [Cilacap Regency, Central Java]..........G. hagen (Ng, Schubart & Lukhaup, 2015)

– Carapace otherwise coloured in life; dorsal margin of dactylus of male chela with 11–13 or small tubercles (last one often very small) ..............................................................................8

8. Male pleon proportionately broader (Fig. 1D); G1 more slender with subdistal part of outer margin more rounded, curved, dorsal section proportionately more slender; chitinous distal part bent 40° along longitudinal axis (Figs. 4D, E, H, I, 6D–F) [Bogor and Lebak Regencies; West Java and Banten] ........................ .............................................. G. noduliferum (De Man, 1892)

– Male pleon proportionately more slender (Fig. 5D); G1 relatively stouter, subdistal part of outer margin more angular, dorsal distal section more strongly developed, chitinous distal part bent 45° along longitudinal axis (Figs. 6G, H, 7B, C) [Lebak Regency; Banten] .................................. G. lebak, (Ng & Wowor, 2019)

9. Ambulatory meri proportionately longer and more slender (Fig. 16A); G1 with chitinous part relatively longer, gently bent 30° along longitudinal axis (Fig. 18B, C, H, I) [Bogor and Sukabumi Regencies; West Java]...................................... ...............................................................G. sekop, (Ng & Wowor, 2019)

– Ambulatory meri proportionately shorter and stouter; G1 with chitinous part relatively shorter, bent 40° along longitudinal axis ......................................................................................... 10

10. Margin of frontal lobe distinctly convex (Fig. 13B); G1 proportionately stouter, chitinous distal part wider in mesial view (Fig. 15B, C) [Cibodas, Cianjur Regency, West Java]... .................................................G. confertum (Ortmann, 1894)

– Margin of frontal lobe gently convex to almost truncate (Figs. 19B, 20A); G1 relatively more slender, chitinous distal part more slender in mesial view (Fig. 21B, C) [Mount Halimun, Bogor Regency, West Java]..............G. cikaniki, (Ng & Wowor, 2019)

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References:

1. NG PKL., & Wowor, D. (2019). The vampire crabs of Java, with descriptions of five new species from Mount Halimun Salak National Park, West Java, Indonesia (Crustacea: Brachyura: Sesarmidae: Geosesarma). Raffles Bulletin of Zoology, 67(1), 217-246.