Arthropoda arthropods, 'jointed legged animals' characterized by segmented bodies and jointed appendages; have gills or tracheae; easily the largest phylum of all animals & of great economic importance, possibly a polyphyletic group --[ToL ucmp ummzADW links] Crustacea crustaceans, mainly graytic animals with gills and a dorsal carapace or shell, includes crabs, lobsters, shrimps etc --[ummzADW links] Branchiopoda branchiopods --[ummzADW links] Anostraca fairy shrimps (Artemia) --[links] Cladocera water fleas (Bosmina, Daphnia) --[links] Conchostraca clam shrimps (Leptestheria) --[links] Notostraca tadpole shrimps (Lepidurus, Triops) --[links] Branchiura fish lice; incl in Maxillopoda of some authors (Argulus, Chonopeltis) Cephalocarida --[ ummzADW links] Cirripedia barnacles; incl in Maxillopoda of some authors (Balanus, Lepas) --[links] Copepoda copepods; incl in Maxillopoda of some authors (Acartia, Calanus, Caligus, Cyclops, Diaptomus, Ergasilus, Harpacticus) --[researchers links] Malacostraca large group with heavily calcified external skeleton, two pairs of well-developed antennae, 8 segments in thorax each with a pair of appendages, 6-7 segments in abdomen; many well known representatives, including: --[ummzADW links] Decapoda --[links] Natantia prawns, shrimps (Alpheus, Crangon, Hippolyte, Macrobrachium, Pandalus, Penaeus) --[links] Reptantia Anomura hermit crabs (Callianassa, Pagurus, Upogebia) --[links] Astacura crayfish, true lobsters (Astacus, Cambarus, Homarus, Nephrops, Orconectes, Procambarus) --[links] Brachyura true crabs (Callinectes C.sapidus -- blue crab, Cancer, Maja, Ocypode, Scylla, Uca) --[links] Palinura slipper lobsters, spiny lobsters (Jasus, Palinurus, Panulirus) --[links] Euphausiacea krill (Meganyctiphanes, Thysanoessa) --[links] Stomatopoda mantis shrimps (Squilla) --[links] Amphipoda amphipods (Corophium, Gammarus, Talorchestia) --[dedicated site links] Cumacea cumaceans --[dedicated site links] Isopoda isopods, pill bugs, woodlice (Armadillidium, Idotea, Ligia, Limnoria, Oniscus, Porcellio) --[ToL links] Mysidacea mysids (Mysis, Neomysis) --[links] Ostracoda ostracods; incl in Maxillopoda of some authors (Candona, Limnocythere) --[links] Trilobitomorpha trilobites, known only from fossils (Calymene, Phacops) --[dedicated site ucmp links]