Order Exocycloida is a taxonomic classification of crustaceans, which includes species of marine arthropods such as barnacles, copepods, and krill. Several synonyms are used to refer to the Order Exocycloida. Some of the synonyms include the terms "podocopid, "exopodite-bearing," and "free legged." These terms reflect the anatomy and biology of the crustaceans in this order. The term "podocopid" refers to the presence of a modified first pair of legs that acts as a feeding appendage. The term "exopodite-bearing" refers to the presence of specialized appendages called exopodites, which aid in swimming or feeding. Finally, the term "free-legged" refers to the mobility of the legs, which are not fused together as in other crustacean orders.