undefined are categorized as invertebrate animals belonging to the subphylum Crustacea. This vast and diverse group primarily consists of aquatic arthropods, encompassing decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, opossum shrimps, amphipods, and mantis shrimp. Within the clade Mandibulata, crustaceans can be treated as a subphylum. Recent findings indicate that the hexapods, which include insects, evolved from within the crustacean group, leading to the completion of the Pancrustacea classification. Notably, the classes Cephalocarida, Branchiopoda, and Remipedia are found to be more closely related to the hexapods than any other crustacean class.