Maxillopoda is a class of Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... crustaceans, characterised by a reduction of the The abdomen (from the Latin word meaning belly) is the part of the body between the pelvis and the thorax. ... abdomen and its appendages. The most species-rich groups are the Orders Ascothoracica Acrothoracica Thoracica Rhizocephala A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea and is hence distantly related to crabs and lobsters. ... barnacles and copepods.