Arthropoda (Phylum) > Crustacea (Subphylum) > Malacostraca (Class) > Eumalacostraca (Subclass) > Eucarida (Superorder) > Decapoda (Order) > Pleocyemata (Suborder) > Brachyura (Infraorder) > Eubrachyura (Section) > Thoracotremata (Subsection) > Ocypodoidea (Superfamily) > Ocypodidae (Family) > Ucinae (Subfamily) > Uca (Genus) > Uca (Gelasimus) (Subgenus)

KEY FEATURES
Carapace 21x34mm (LxW); fiddle to 55mmL. CARAPACE very narrow between the eyes (a "narrow-fronted fiddler-crab"). COLOUR contrasting morphs - blue-black with pale lattice or blotches, and yellow with cream blotches and dark spots. MALE "fiddle" (=chela or cheliped) red to pink base with dark band over base of fixed-finger (=pollex); an indistinct long-triangular depression extending about 25% along the fixed-finger (pollex); a granular surface on the base of the fiddle; and a dorsal spine on the wrist segment (=merus). FEMALE has patch of hairs on each posterior corner of carapace.

SIMILAR SPECIES
Uca crassipes has a broad projection between the eyes (vs. narrow projection); sharp-edged short-triangular pit at the base of the fixed-finger (vs. indistinct long-triangular depression); without dark-bar on base of fixed-finger (vs. usually with dark bar).

SYNONYMES
Cancer tetragonon (Herbst, 1790)
Gelasimus tetragonon (Herbst)
Gelasimus tetragonon (var. spinicarpa Kossmann, 1877)
Gelasimus variatus (Hess, 1865)
Uca affinis (Guérin, 1829)
Uca duperreyi (Guérin, 1829)