Percnon planissimum
Carapace nearly subcircular (slightly longer than broad) and flattened with smooth dorsal surface covered with small setae. Anterolateral with three teeth. Frontal margin characterized by a pair of distinctive clefts. Dorsal margin of pereiopod merus with spines.
Vernacular name: Reef surf crab.
These crabs reside in subtidal areas with very strong currents or places with strong surfs. To ensure they are not washed away, they have long powerful legs lined with spines to improve their grip and flat carapaces to reduce drag. They are mostly algivores.
Order Decapoda Latreille, 1802
Infraorder Brachyura Latreille, 1802
Section Eubrachyura de Saint Laurent, 1980
Subsection Heterotremata Guinot, 1977
Superfamily Grapsidoidea Macleay, 1838
Family Plagusiidae Dana, 1851
Percnon planissimum Herbst, 1804
East Africa to Hawaii, including Thailand, South China, Taiwan, Japan and Australia (NE, NSW).
Rocky shore reefs intertidally.