An asterisk (*) marks the crabs included in the clade Thoracotremata.
Crabsare decapodcrustaceansof theBrachyurainfraorder or division.
As members of the order Decapoda, which also includes crayfish,lobsters, prawns, andshrimp, crabs have ten legs: the last five pairs of the eight pairs of thoracic appendages characteristic of crustaceans. As members of the Brachyura taxon, crabs typically have a very short tail or the abdomen is entirely hidden under the thorax ((Greek:brachy= short,ura= tail). Crabs typically are characterized by the first pair of the five pairs of appendages being modified into chelae (claws), a thickexoskeleton, and an upper body shield or carapace that is generally broad, hard, and flattened.