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