### Identification The Angular Crab (*Goneplax rhomboides*) is a geometric marvel of the muddy seafloor. Unlike the rounded silhouettes of most crabs, its carapace is starkly rectangular—wider than it is long—with a smooth, polished surface ranging from pale yellowish-white to a delicate pinkish-orange. Look for two sharp, thorn-like spines on the front corners of the shell. The most striking field mark, however, belongs to the males: they possess exceptionally long, slender chelipeds (pincers) that can be up to five times the length of their body. Their eyestalks are equally elongated, folding into deep grooves along the front of the shell like retractable periscopes.
### Habitat & Range This species is a specialist of the "sticky" stuff. It thrives in fine-grained muddy or sandy-mud substrates on the continental shelf, typically at depths of 10 to 100 meters. You’ll find them throughout the Northeast Atlantic, from the rocky coasts of the British Isles down to South Africa, as well as across the Mediterranean. They are rarely seen by beachgoers, as they remain offshore in the sublittoral zone.
### Behaviour Angular Crabs are the master architects of the seabed. They are tireless excavators, spending their days in complex, Y-shaped burrow systems with multiple circular entrances. Primarily nocturnal, they emerge at dusk to forage or defend their territory. If threatened, they use those spindly, elongated claws not just for pinching, but as "fencing foils" to keep rivals at a distance.
### Diet An opportunistic scavenger and predator, *G. rhomboides* sifts through the silt for small benthic invertebrates, such as polychaete worms and tiny mollusks. They also feed on organic detritus that settles into the mud, using their smaller mouthparts to filter nutrients from the sediment.
### Fascinating Fact The Angular Crab is a generous landlord! Its deep, oxygenated burrows are frequently shared with the Fries's Goby (*Lesueurigobius friesii*). This "odd couple" relationship is a classic example of commensalism, where the fish gains a safe home, and the crab gains a vigilant roommate that helps stir up the sediment.