Uca

Shih, Hsi-Te, Ng, Peter K. L., Fang, Shou-Hua, Chan, Benny K. K. & Wong, Kingsley J. H., 2010, Diversity and distribution of fiddler crabs (Brachyura: Ocypodidae: Uca) from China, with new records from Hainan Island in the South China Sea, Zootaxa 2640, pp. 1-19 : 2-3

Key to the Uca species recorded from China

1. Front narrow; outer surface of manus of major cheliped with tubercles ...................................................................... 2

- Front wide; outer surface of manus of major cheliped smooth. ................................................................................. 10

2. Anterolateral margin long; merus of first 3 ambulatory legs wide............................................................................... 3

- Anterolateral margin short; merus of first 3 ambulatory legs slender .......................................................................... 4

3. Carapace strongly arched, postero-lateral striae absent; size large (CW to ~ 37 mm) .................................. U. arcuata

- Carapace not strongly arched, postero-lateral striae present; size moderately small (CW to ~ 25 mm) .......... U. acuta

4. Dactyl of major cheliped without groove; suborbital crenulations large, distinct........................................................ 5

- Dactyl of major cheliped with 1 or 2 grooves; suborbital crenulations small, indistinct ............................................. 7

5. Outer surface of manus of major cheliped with small tubercles; fingers narrow, thick; pollex without groove; female with setae posteriorly on carapace sides ................................................................................................... U. tetragonon

- Outer surface of manus of major cheliped with large tubercles; fingers broad, flat; pollex with 1 groove; female without setae posteriorly on carapace sides .................................................................................................................. 6

6. Pollex of major cheliped with shallow or without distal depression, dactylus deeper than pollex only in young; oblique ridge of major manus low ................................................................................................................ U. borealis

- Pollex of major cheliped with both deep proximal and distal depressions, dactylus not deeper than pollex; oblique ridge of major manus high .............................................................................................................................. U. vocans

7. Floor of orbit with a row of tubercles; fingers of major cheliped with 1 groove ......................................................... 8

- Floor of orbit without a row of tubercles; fingers of major cheliped with 2 grooves................................................... 9

8. Floor of orbit with a long row of tubercles (often ≥ 15); fingers of major cheliped with 1 shallow groove; female without large tooth on either finger ................................................................................................................ U. typhoni

- Floor of orbit with a short row of tubercles; fingers of major cheliped with 1 deep groove; female with a large tooth at least on one finger ................................................................................................................................... U. coarctata

9. Front with distinct narrow median groove; G1 with distal spiniform chitinous process; female without large tooth on either finger; size large (CW to ~ 38 mm) ........................................................................................ U. paradussumieri

- Front almost without discernible median groove, but clearly separated; G1 with distal blunt chitinous process; female always with a large tooth on both fingers; size medium (CW to ~ 27 mm) ................................. U. dussumieri

10. Shallow, triangular depression outside pollex base; 4th ambulatory merus broad, dorsal margin convex U. crassipes

- No triangular depression outside pollex base; 4th ambulatory merus slender, dorsal margin straight....................... 11

11. Dactylus of major cheliped with 2 grooves; posterior carapace medium narrow; orbits very oblique .. U. triangularis

- Dactylus of major cheliped without groove; posterior carapace slight narrow; orbits not oblique............................ 12

12. Pollex of major cheliped without or with small predistal triangular tooth; G1 with posterior flange longer, broader than anterior ..................................................................................................................................................... U. lactea

- Pollex of major cheliped with small to moderate predistal triangular tooth; G1 with anterior flange longer, broader than posterior .............................................................................................................................................. U. annulipes