Description: This crab’s carapace is oval in shape and reaches a size of up to 50 mm. The surface of the carapace is reddish-brown with some small grooves and ridges. There are three teeth between the eyes, with the middle one most pronounced. There are 9-11 prominent and broad, pointed teeth on each side of the carapace, with the fourth and tenth being the smallest. There are dense bristles on the sides and underside towards the back of the animal, with the bristles longest between the eighth and tenth set of teeth. Pincers are evenly sized and densely bristled on the underside.

Habitat: Recorded from the lower shore on coarse sand and reported to be found on maerl beds.

Distribution: Found all around Britain and Ireland but rarely recorded from west coast of Ireland.

Similar Species: Could be confused with Atelecyclus rotundatus although it has a circular carapace rather than oval, and it also lacks the dense bristles.

Key Identification Features:

• Oval carapace.
• 9-11 prominent, broad and pointed teeth on each side of carapace.
• Fourth and tenth set of teeth smallest.
• Side and underside has dense bristles, with longest bristles between eighth and tenth set of teeth.

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

iNaturalist: Atelecyclus undecimdentatus at iNaturalist World Species Observations database.

WoRMS: Atelecyclus undecimdentatus at World Register of Marine Species. Accepted name: Atelecyclus undecimdentatus (Herbst, 1783). AphiaID: 107274.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Brachyura; Eubrachyura; Heterotremata; Cancroidea; Atelecyclidae; Atelecyclus