There are 2.16 million species out there, to sort them out, the following is a list of the classes in each phylum of the kingdom Animalia. There are 107 classes of animals in 33 phyla in this list. However, different sources give different numbers of classes and phyla. For example, Protura, Diplura, and Collembola are often considered to be the three orders in the class Entognatha. This list should by no means be considered complete and authoritative and should be used carefully.
Acanthocephala (thorny-headed worms) Archiacanthocephala Eoacanthocephala Palaeacanthocephala (ancient thornheads)
Acoelomorpha (simple soft-bodied flatworms) Acoela Nemertodermatida
Annelida (segmented worms)
Clitellata (earthworms) Polychaeta (bristle worms) Sipuncula (peanut worms)
Arthropoda (arthropods: insects, crustaceans, arachnids, centipedes, and millipedes)
Chelicerata
Arachnida (spiders, scorpions, and kin) Xiphosura (horseshoe crabs) Pycnogonida (sea spiders)
Crustacea
Branchiopoda (fairy shrimp, tadpole shrimp, water fleas, and clam shrimp) Cephalocarida (horseshoe shrimp) Pentastomida (tongue worms) Branchiura (fish lice) Mystacocarida Copepoda Ostracoda (seed shrimp) Malacostraca (crabs, lobsters, crayfish, krill, various shrimp, woodlice, and kin) Thecostraca (barnacles) Remipedia
Hexapoda
Entognatha (coneheads, two-pronged bristletails and springtails) Insecta (insects)
Myriapoda
Chilopoda (centipedes) Diplopoda (millipedes) Pauropoda Symphyla (pseudocentipedes)
Brachiopoda ("lamp shells") Lingulata Craniata Rhynchonellata
Bryozoa (moss animals) Gymnolaemata Phylactolaemata Stenolaemata
Chaetognatha (arrow worms) Sagittoidea
Chordata (vertebrates, tunicates, and lancelets)
Cephalochordata
Leptocardii (lancelet)
Tunicata
Appendicularia (larvaceans) Ascidiacea (sea squirts, paraphyletic with respect to Thaliacea) Thaliacea (salps, pyrosomes, and doliolids)
Vertebrata
Agnatha
Cyclostomata
Myxini (hagfish) Petromyzontida (lamprey)
Gnathostomata
Chondrichthyes (cartilaginous fish: chimeras, sharks and rays)
Osteichthyes
Actinopterygii (ray-finned fish, which includes most familiar bony fish) Sarcopterygii Actinistia (coelacanths) Dipnoi (lungfish) Tetrapoda Amphibia (amphibians) Amniota Mammalia (mammals) Aves (birds) Reptilia (reptiles, paraphyletic with respect to Aves)
Cnidaria (marine stinging animals) Octocorallia Hexacorallia Ceriantharia Cubozoa (box jellyfish) Hydrozoa (hydroids) Myxozoa (marine parasites) Scyphozoa (true jellyfish) Staurozoa (stalked jellyfish) Polypodiozoa (marine parasites)
Cycliophora (tiny marine animals) Eucycliophora
Dicyemida (rhombozoa) Dicyemida
Echinodermata (starfish, sea urchins, sand dollars, sea lilies, and others)
Crinozoa
Crinoidea (sea lilies and feather stars)
Asterozoa
Asteroidea (star fish) Ophiuroidea (brittle stars)
Echinozoa
Echinoidea (sea urchins) Holothuroidea (sea cucumbers)
Entoprocta
Entoprocta
Gastrotricha (hairybacks) Gastrotricha
Gnathostomulida (jaw worms) Gnathostomulida
Hemichordata
Enteropneusta (acorn worms) Pterobranchia
Kinorhyncha (mud dragons) Allomalorhagida Cyclorhagida
Loricifera
Loricifera
Mollusca (mollusks) Aplacophora Bivalvia (clams, mussels, scallops, and kin) Cephalopoda (octopuses, squids and cuttlefish) Gastropoda (snails and slugs) Monoplacophora Polyplacophora (chitons, or sea cradles) Scaphopoda (tusk shells)
Micrognathozoa
Micrognathozoa
Nematoda (roundworms) Chromadorea Enoplea Secernentea
Nematomorpha (horsehair worms) Gordioidea Nectonematoida
Nemertea (ribbon worms) Anopla Enopla
Onychophora (velvet worms) Udeonychophora
Orthonectida
Orthonectida
Placozoa
Polyplacotomia
Uniplacotomia
Platyhelminthes (flatworms) Cestoda (tapeworms and relatives) Monogenea Trematoda (flukes) Turbellaria (e.g. Dugesia)
Porifera (sponges) Calcarea (calcareous sponges) Demospongiae Hexactinellida (glass sponges) Homoscleromorpha
Priapulida (priapulid worms) Halicryptomorpha Priapulimorpha Seticoronaria
Rotifera (rotifers) Bdelloidea Monogononta Seisonidea
Tardigrada (tardigrades, water bears, or moss piglets) Eutardigrada Heterotardigrada