Why crustaceans keep evolving to look like crabs, and how to tell 'true' crabs from 'false' ones

Few animals are as recognisable as the crab: a rounded, flat body covered in a hard shell, attached to scuttling legs and a pair of pincers.

But not everything that looks like a crab is, technically, a true crab.

Crustaceans have evolved a crab-like body at least five times, resulting in thousands of species of "false crabs".