KEY TO SPECIES OF CARCINOPLAX H. MILNE EDWARDS, 1852

1. One well-developed, anteriorly curved anterolateral tooth posterior to outer orbital tooth on each side of carapace (Guinot 1989: pl. 13, fig. F, as C. eurysternum Guinot & Richer de Forges, 1981) ................................. ..................................................................................................................... C. ischurodous (Stebbing, 1923) .

— Two anterolateral teeth posterior to outer orbital angle (1 or 2 anterolateral teeth may be greatly reduced or even obsolete in some large individuals) .............................................................................................................. 2

2. Adults attain large size (cl more than 30-40 mm), with reduced outer orbital and anterolateral teeth (obsolete in largest individuals), rounded anterolateral borders (carapace becoming almost spherical), and much enlarged chelipeds (P1) with conspicuously elongated meri, propodi ......................................................................... 3

— Adults do not attain large size (cl less than 30-40 mm), do not show progressive reduction in outer orbital (if present) and anterolateral teeth with corresponding rounded anterolateral borders and chelipeds (P1) with conspicuously elongated meri, propodi ............................................................................................................. 8

3. Low, conspicuous granules on carapace; small individuals with triangular, acute, curved, acute first and second anterolateral teeth (Guinot 1989: pl. 1, fig. D); uniformly red to dark red-brown carapace in life, bright redbrown markings on chelipeds (P1) ............................................................... C. longimana (De Haan, 1833) .

— No conspicuous granules on carapace; small individuals with narrow, acute anterolateral teeth, or small, blunt first anterolateral teeth; in life, carapace not uniformly red or dark-red brown ............................................. 4

4. Small- to medium-size individuals with 2 narrow, acute, spine-like anterolateral teeth below acute, conspicuous outer orbital tooth on each side of carapace (Guinot 1989: pl. 1, figs G, H; Hsueh & Huang 2002: fig. 6A); carapace nearly quadrate, with red, round spot on dorsal surface in most individuals when fresh (Hsueh & Huang 2002: fig. 8B) ............................................................................................... C. indica Doflein, 1904 .

— Small- to medium-size individuals with blunt first anterolateral tooth, second tooth curved, acute; carapace globose; never with red spot on carapace in life ........................................................................................... 5

5. Outer orbital angle with low tooth or absent; second anterolateral tooth short, low (more conspicuous in small individuals), not hook-like .......................................................................................................................... 6

— Outer orbital angle with distinct tooth; second anterolateral tooth usually distinct, elongated, hook-like .... 7

6. P2-P5 relatively short; anterolateral teeth may be low in larger individuals but always visible (Ng & Mitra 2019: fig. 6C, D); purple-red vertical band across carapace from front to posterior border in life (Hsueh & Huang 2002: fig. 8C); western Pacific ............................................................................ C. purpurea Rathbun, 1914 .

— P2-P5 relatively longer; anterolateral tooth short, absent in large individuals (Guinot 1989: fig. 9A-C; pl. 3, figs A, C, E); carapace uniformly colored in life; Red Sea and Persian Gulf ............. C. monodi Guinot, 1989 .

7. G1 with rounded, truncated tip (Ng & Mitra 2019: fig. 8K, L, N); western Pacific ..... C. sinica Chen, 1984 . — G1 with pointed tip (Ng & Mitra 2019: fig. 8E, F); Indian Ocean ................... C. mistio Ng & Mitra, 2019 .

8. Carapace, chelipeds (P1), and P2-P5 covered with conspicuous short setae ................................................. 9

— Carapace, chelipeds (P1), and/or P2-P5 may have sparse setae, short tomentum, or mostly or completely devoid of conspicuous setae, or tomentum ........................................................................................................... 10

9. Conspicuous, acute tubercles on proximal portion of P1 propodi (may be absent in large individuals) (Hsueh & Huang 2002: fig. 5E); distal quarter of fingers darkly pigmented; acute tooth on distal portion of P2-P5 meri (Chen 1998: fig. 4-2; Hsueh & Huang 2002: fig. 5C); no conspicuous color pattern in life …....................... ...................................................................................................................... C. spinosissima Rathbun, 1914 .

— Conspicuous, low, blunt tubercles on proximal portion of cheliped (P1) propodi (Guinot 1989: pl. 6, fig. H); distal half of fingers darkly pigmented; distal portion of P2-P5 meri smooth; in life with orange reticulated lines on P1 and carapace (obvious when denuded) ............................................................. C. nana Guinot, 1989 .

10. Carapace, chelipeds (P1), and P2-P5 covered with short tomentum (large individuals only on ambulatory legs) (Hsueh & Huang 2002: fig. 7A) ............................................................................ C. tomentosa Sakai, 1969 .

— Carapace, chelipeds (P1), and P2-P5 not covered with conspicuous short tomentum ................................ 11

11. Outer orbital angle without tooth or eminence; with 2 thin, spine-like anterolateral teeth (Castro 2007: figs 4A, 5) ..................................................................................................................... C. tenuidentata Castro, 2007 .

— Outer orbital angle ends in lobe or tooth; anterolateral teeth not thin, spine-like ...................................... 12

12. Front with slight median notch (Guinot 1989: fig. 17) .................................... C. confragosa Rathbun, 1914 . — Front straight, without distinct median notch. ........................................................................................... 13 13. Conspicuous, well-developed anterolateral teeth, with acute, anteriorly-oriented or hook-like tips ............ 18 — Relatively small, blunt, non-spinous anterolateral teeth (Castro 2007: figs 7, 10) ...................................... 24

14. P2-P5 long, relatively slender, distal end of folded P5 merus extending beyond tip of second anterolateral tooth ......................................................................................................................................................... 15

— P2-P5 short, distal end of folded P5 merus only reaching or barely reaching tip of second anterolateral tooth .................................................................................................................................................................. 16

15. Two conspicuous, wide transverse ridges on dorsal surface of carapace (Castro 2007: fig. 3); western Pacific .. ................................................................................................................................. C. cracens Castro, 2007 .

— Dorsal surface of carapace evenly convex, without transverse ridges; eastern Indian Ocean ............................. .................................................................................................................. C. longipes (Wood-Mason, 1891) .

16. Two conspicuous, wide transverse ridges on dorsal surface of carapace ............. C. inaequalis (Yokoya, 1933) . — Dorsal surface of carapace evenly convex, without conspicuous ridges. ...................................................... 17

17. All anterolateral teeth anteriorly curved; narrow, J-shaped gap between outer orbital tooth and first anterolateral tooth (Castro 2009: fig. 1A); southwestern and central Pacific .............................. C. uncinata Castro, 2009 .

— Anterolateral teeth sharp but not curved (only first one in rare cases); outer orbital angle often prominent, rounded. ................................................................................................................................................... 18

18. Posterior margin of epistome with median part pronounced, triangular, lateral margins conspicuously concave (Fig. 21D) ................................................................................................................................................. 19

— Posterior margin of epistome with truncated or nearly straight median part; lateral margins nearly straight or slightly sinuous (Fig. 3D) .......................................................................................................................... 20

19. Two transverse elevations across cardiac, gastric regions of carapace (Figs 21C, D; 22C, D); western Pacific ... ............................................................................................................................................... C. jugum n. sp.

— Dorsal surface of carapace evenly smooth, without transverse elevations; western Indian Ocean ..................... ...................................................................................................................... C. fasciata Ng & Kumar, 2009 .

20. Outer, proximal margin of cheliped carpus with sharp tooth; western Pacific and eastern Indian Ocean ......... .................................................................................................................................. C. polita Guinot, 1989 .

— Outer, proximal margin of cheliped carpus smooth, without tooth ........................................................... 21

21. P2-P5 proportionally short, stout, with distal end of folded P5 merus not reaching tip of second anterolateral tooth (e.g. Figs 10A; 11A; 19A; 20A) ........................................................................................................ 22

— P2-P5 proportionally long, slender, with distal end of folded P5 merus reaching tip of second anterolateral tooth (e.g. Figs 2A; 3A; 13A; 14A) ..................................................................................................................... 23

22. Posterior margin of epistome with median part not protruding (Figs 19D; 20D); G1 elongated, distal half distinctly slender (Fig. 25F); southwestern Pacific .................................................................... C. adelphia n. sp.

— Posterior margin of epistome with median part pronounced, protruding (Figs 10D; 11D; 12D); G1 relatively short, stout (Fig. 25A, B); northwestern Pacific ................................................. C. specularis Rathbun, 1914 .

23. Fingers dark brown or black almost along their entire lengths (Figs 2H; 3I; 4H; 5H); inner distal angle of carpus of cheliped dentiform (Figs 2E, F; 3F, 4F, 5E); Indian Ocean and southwestern Pacific .................................. ............................................................................................................................ C. abyssicola (Miers, 1885) .

— Fingers dark brown or black along the distal two-thirds to half portions (Figs 13I, J; 14H); inner distal angle of carpus of cheliped usually spiniform with tip narrow (Figs 13F; 14F; 15E); western Pacific ............................ ........................................................................................................................... C. verdensis Rathbun, 1914 .

24. Outer, dorsal surface of cheliped (P1) propodi and carpi with conspicuous granular tubercles (Castro 2007: fig. 8); P2-P5 relatively short (Fig. 7), distal end of folded P5 merus only reaching tip of second anterolateral tooth; western Pacific ............................................................................................. C. tuberosa Castro, 2007 .

— Outer, dorsal surface of chelipeds (P1) smooth; P2-P5 proportionally long (Castro 2007: fig. 10), distal end of folded P5 merus extending beyond tip of second anterolateral tooth; central and southwestern Pacific ........... ................................................................................................................................ C. velutina Castro, 2007 .