Convergent evolution

independent evolution of similar features in species of different lineages; creates analogous structures

name of various species of extinct mammals

thumb|Porcelain crabs resemble true crabs, but are more closely related to [[squat lobsters and hermit crabs.]]

thumb|upright=1.35|Cancer pagurus, the edible or brown crab ([[Brachyura)]] Crabs are decapod crustaceans, either the Brachyura (the "true crabs") or various groups within the closely related Anomura (hermit crabs and allies), characterised by having a heavily armoured shell, their tail segments concealed under the body, the ability to run sideways, and the habit of hiding in rocky crevices. They do not form a single natural group or clade, but have convergently evolved multiple times from the ancestral decapod body plan through carcinisation, the process of creating this set of characteristic