Description: A small spider crab which can have a triangular carapace up to 20 mm in length. The colour of the carapace is usually brown to yellowish red in colour, with the pincers and legs a lighter colouration, although the colour and features are often obscured by fauna growing on the crab’s body. There is a narrow v-shaped rostrum between the eyes. The eyestalks are covered with short bristles, as are the legs and carapace (although this is often not visible due to epifauna). Males have much larger pincers than the females. The first pair of walking legs is noticeably wider than the others.

Habitat: Found from the lower shore (rarely) to around 50 m. Usually on sand.

Distribution: Recorded all around Britain and Ireland.

Similar Species: Could be confused with other Inachus spp. Inachus dorsettensis has a wide U-shaped rostrum while Inachus phalangium has a narrow v-shaped rostrum and Inachus leptochirus has a narrow u-shaped rostrum.

Key Identification Features:

• Triangular carapace, usually covered in epifauna.
• Narrow v-shaped rostrum between the eyes.
• First pair of walking legs wider/thicker than the others.

Distribution Map from NBN: Inachus phalangium at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Inachus phalangium at iNaturalist World Species Observations database.

WoRMS: Inachus phalangium at World Register of Marine Species. Accepted name: Inachus phalangium (Fabricius, 1775). AphiaID: 107333.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Brachyura; Eubrachyura; Heterotremata; Majoidea; Inachidae; Inachinae; Inachus