Question: is a crab a fish or a mammal

title: Crab
text: Crabs are decapod crustaceans of the infraorder Brachyura , which typically have a very short projecting `` tail '' ( abdomen ) ( Greek : βραχύς , translit . brachys = short , οὐρά / οura = tail ) , usually entirely hidden under the thorax . They live in all the world 's oceans , in fresh water , and on land , are generally covered with a thick exoskeleton and have a single pair of claws . Many other animals with similar names -- such as hermit crabs , king crabs , porcelain crabs , horseshoe crabs , and crab lice -- are not true crabs . 

Answer: answer: Crabs are decapod crustaceans, many other animals with similar names - such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice - are not true crabs.