Data S1. Key to taxonomic groupings
BILATERIAN OUTGROUPS
Porifera (sponges)
Ctenophora (comb jellies)
Cnidaria
Anthozoa (corals, sea anemones, sea pens)
Hydrozoa (hydroids and hydromedusae)
Scyphozoa (true jellyfish)
BILATERIA
Acoelomorpha (acoels and nemertodermatids)
PROTOSTOMATA
(mouth and anus derive from the blastopore)
Ecdysozoa (clade of moulting animals)
Priapulida (microscopic burrowing worms; penis worms)
Kinorhyncha (microscopic spiny-headed worms)
Nematoda (roundworms)
Onychophora (velvet worms; soft bodies and unsegmented legs)
Tardigrada (water bears; clawed legs, exoskeleton)
Arthropoda (most speciose metazoan phylum)
Hexapoda (arthropods with six walking legs)
Collembola (direct developing, wingless; springtails)
Insecta
Diptera (true flies with one pair of functional wings)
Hymenoptera (membrane-winged insects: bees, wasps, ants)
Lepidoptera (scale-winged insects: moths, butterflies)
Crustacea
Cladocera (microscopic branchiopod crustaceans)
Copepoda (planktonic maxillopodan crustaceans)
Cheliceriformes (spiders, scorpions, horseshoe crabs, sea spiders)
Arachnida (eight walking legs)
Myriapoda (millipedes and centipedes)
Chaetognatha (arrow worms)
Lophotrochozoa(clade of animals with lophophores or trochophore larvae)
Rotifera (microscopic aquatic invertebrates with an oral crown of cilia)
Platyhelminthes
Cestoda (tapeworms)
Trematoda (flukes)
Turbellaria (free-living flatworms)
Gastrotricha (microscopic worms, marine and freshwater)
Phoronida (lophophorates known as horseshow worms)
Brachiopoda (lamp shells)
Ectoprocta (also known as Bryozoa; moss animals)
Entoprocta (small animals superficially similar to some Ectoprocts and hydroids)
Nemertea (unsegmented ribbon or proboscis worms)
Annelida (segmented worms)
Hirudinea (leeches)
Oligochaeta (earthworms, segmented freshwater worms)
Polychaeta (marine worms including tube and fan worms)
Pogonophora (beard worms)
Echiura (unsegmented benthic coelomate worms)
Sipunculida (peanut worms: unsegmented, U-shaped gut, dorsal anus)
Mollusca
Aplacophora (shell-less marine molluscs)
Bivalvia (clams, mussels)
Cephalopoda (squid, octopi, cuttlefish)
Gastropoda (snails, slugs)
Gnathostomulida (microscopic vermiform animals with monociliated epidermis)
DEUTEROSTOMATA
(mouth is not derived from blastopore)
Echinodermata
Asteroidea (sea stars)
Crinoidea (sea lilies, feather stars)
Echinoidea (sea urchins)
Holothuroidea (sea cucumbers)
Hemichordata
Enteropneusta (acorn worms)
Pterobranchia (colonial hemichordates)
Chordata
Urochordata (tunicates or sea squirts)
Cephalochordata (lancelets: Amphioxus)
Vertebrata
Agnatha* (jawless vertebrates: hagfish and lampreys)
Gnathostomata (jawed vertebrates)
Chondrichthyes (sharks, rays and chimaeras)
Osteichthyes (bony fish and tetrapods)
Actinopterygii (ray-finned bony fish)
Teleostei (modern bony fish, including zebrafish and sticklebacks)
Sarcopterygii (lobe-finned fish and tetrapods)
Dipnoi (lungfish)
Tetrapoda
Amphibia
Anura (frogs and toads)
Urodela (newts, axolotls, and salamanders)
Amniota (terrestrial vertebrates whose eggs contain an amnion)
Sauropsida (living and extinct reptiles, dinosaurs and birds)
Testudines (turtles, terrapins and tortoises)
Squamata (snakes and lizards)
Archosauria (crocodiles, pterosaurs, dinosaurs and birds)
Aves (birds)
Synapsida (mammals and extinct mammal-like reptiles)
Mammalia
Monotremata (egg-laying mammals)
Metatheria (marsupials)
Eutheria (placental mammals)
Legend
BILATERIAN CLADES
Protostome clades
Phyla
Subphyla
Classes
Subclasses
Orders
Large monophyletic groups
*Paraphyletic group