Any member of the crustacean order Decapoda, comprising species possessing 5 pairs of jointed, thorassic limbs such as crabs, crayfish, lobsters and shrimp. Also used historically in reference to molluscs of the Cephalopod superorder Decapodiformes, members of which have 8 short limbs plus 2 longer tentacles and include cuttlefish and squid.