Unknown phylum
- Micrognathozoa
Acanthocephala (thorny-headed worms)
- Archiacanthocephala
- Eoacanthocephala
- Palaeacanthocephala (ancient thornheads)
Acoelomorpha (simple soft-bodied flatworms)
- Acoela
- Nemertodermatida
Annelida (segmented worms)
- Aelosomata
- Clitellata (earthworms)
- Myzostomida
- Polychaeta (bristle worms)
- Echiura (spoon worms)
- Sipuncula (peanut worms)
Arthropoda (arthropods: insects, crustaceans, arachnids, centipedes, and millipedes)
Chelicerata
- Arachnida (spiders, scorpions, and kin)
- Xiphosura (horseshoe crabs; only 4 extant species)
- Pycnogonida (sea spiders)
Crustacea
- Branchiopoda (fairy shrimp, tadpole shrimp, water fleas, and clam shrimp)
- Cephalocarida (horseshoe shrimp; only 12 described species)
- Malacostraca (crabs, lobsters, crayfish, krill, various shrimp, woodlice, and kin)
- Maxillopoda (barnacles, copepods, fish lice, and other groups)
- Ostracoda (seed shrimp)
- Remipedia
Hexapoda
- Entognatha (coneheads, two-pronged bristletails and springtails)
- Insecta (insects)
Myriapoda
- Chilopoda (centipedes)
- Diplopoda (millipedes)
- Pauropoda
- Symphyla (pseudocentipedes)
Brachiopoda (“lamp shells”)
- Craniforma
- Rhynchonellata
Bryozoa (moss animals)
- Gymnolaemata
- Phylactolaemata
- Stenolaemata
Chaetognatha (arrow worms)
- Archisagittoidea
- Sagittoidea
Chordata (vertebrates, tunicates, and lancelets)
Cephalochordata
- Leptocardii (lancelet)
Tunicata
- Appendicularia (larvaceans)
- Ascidiacea (sea squirts)
- Sorberacea
- Thaliacea (salps, pyrosomes, and doliolids)
Vertebrata
Agnatha
Cyclostomata
- Myxini (hagfish)
- Petromyzontida (lamprey)
Gnathostomata
- Chondrichthyes (cartilaginous fish, mostly sharks and rays)
Tetrapoda
- Amphibia (amphibians)
- Amniota
- Mammalia (mammals)
- Aves (birds)
- Reptilia (reptiles)
Osteichthyes
- Actinopterygii (ray-finned fish, which includes most familiar bony fish)
- Sarcopterygii (lobe-finned fish)
Cnidaria (marine stinging animals)
- Anthozoa (anemones and corals)
- Cubozoa (box jellyfish)
- Hydrozoa (hydroids)
- Malacosporea (marine parasites)
- Myxosporea (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)
- Kinorhyncha
Loricifera
- Loricifera
Mollusca (mollusks)
- Bivalvia (clams, mussels, scallops, and kin)
- Caudofoveata
- Cephalopoda (octopuses, squids and cuttlefish)
- Gastropoda (snails and slugs)
- Monoplacophora
- Polyplacophora (chitons, or sea cradles)
- Scaphopoda (tusk shells)
- Solenogastres
Nematoda (roundworms)
- Adenophorea
- Chromadorea
- Secernentea
Nematomorpha (horsehair worms)
- Gordioidea
- Nectonematoida
Nemertea (ribbon worms)
- Anopla
- Enopla
Onychophora (velvet worms)
- Udeonychophora
Orthonectida
- Orthonectida
Placozoa
- Trichoplacoidea
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
Xenoturbellida
- Xenoturbellida
