(demosponge) |
(flatworm) |
KINGDOM ANIMALIA
(=Metazoa)* |
(featherduster worm) |
(sea urchin) |
(octocoral) |
(gastropod) |
Modified from
Tree of Life (after Ruppert & Barnes 2004 p. 220; Brusca & Brusca 2003 p. 875) |
(crab) |
(sea squirts) |
========================================== Porifera (sponges) | | ======================================= Placozoa (placozoans, Trichoplax) | | | | =================================== Cnidaria (jellyfish, anemones, corals, etc.) | | | <<=M=| | | ================================ Ctenophora (comb-jellies) | | | | | | | | ======================== Platyhelminthes (flatworms, tapeworms,etc.) | | | | | =T=| | | | =(branch uncertain)= Aschelminthes (nematodes, rotifers,etc.) | | | | | | | | =P==| | ================ Nemertea (ribbon worms) | | | | | | | =E==| | | =A==| | ======= Mollusca (snails, clams, squids, etc.) | | | | | ======| | | | =C==| | ======= Sipuncula(peanut worms) | | | | | | | | | | ==== Annelida (segmented worms) | | | ===| ===| | | | | ===| ==== Pogonophora (beard worms, vent worms; now put in the Annelida) ===| | | | | | | ===| ======= Echiura (proboscis worms) | | | | | | ======= Onychophora (velvet worms) | | ===| | | | ==== Tardigrada (water bears) | | ===| =B==| ==== Arthropoda (insects, spiders, crabs, etc.) | | ===================== Chaetognatha (arrow worms) | | | |==================== lophophorates (bryozoans, brachiopods, etc.) | | ==DA===| ============ Echinodermata (starfish, urchins, etc.) | ===| ======| ============ Hemichordata (acorn worms, pterobranchs) | =============== Chordata (sea squirts, vertebrates, etc.)
TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):
b) sessile adult, superficial radial symmetry** c) monociliated cells** d) radial, indeterminate cleavage e) blastula stage embryo f) diplosome** g) type IV collagen T: motile adults; dorso-ventral body axis, true radial symmetry b) diploblastic organization c) gastrula stage embryo d) blind gut (no anus) e) true gonads f) true nervous system with synapses g) striated muscle b) cephalization c) triploblastic organization (extensive mesoderm) d) organ-system level of organization e) protonephridia |
b) mesoderm from single (mesentoblast) cell c) mesoderm develops from mesenchyme cells c) fate of first derm cell set at 5th cleavage d) mouth (and sometimes anus) from blastopore e) sheets of subepidermal muscles f) multiciliated cells A: anus present (i.e., complete gut) b) trochophore-like larva with apical cilia c) larvae swim with compound cilia b) mesoderm from epithelial cells c) coelom via enterocoely d) blastopore yields anus e) tripartite coelom and body plan f) monociliated cells** (some multiciliated) |
Important differences include:
- Wolf, Y. I. et al. (2004). Coelomata and not Ecdysozoa: Evidence from genome-wide phylogenetic analysis. Genome Research 14(1): 29-36.
- Hughes, A. L. and R. Friedman (2004). Shedding genomic ballast: Extensive parallel loss of ancestral gene families in animals. Journal of Molecular Evolution 59: 827-833.
For another detailed consideration of phylogenetic relations that includes fossil taxa and references to the original literature, see Mikko's Phylogeny Archive.