NOTE: The cladograms posted on these pages were assembled using selected information from several sources (but see Important Notes About Animal Relations below), including:

• The Tree of Life web site: http://tolweb.org/tree/phylogeny.html

• Andrade, S.C.S et al. 2015. Phylogenomics & annelid relationships. Mol. Biol. Evol. 32:2860-2875.

• Brusca, R.C. & G.J. Brusca. 2016. Invertebrates, Sinauer, 3rd ed.

• Delsuc et al. 2006. Tunicates not cephalochordates are closest living relatives of vertebrates. Nature 439:965.

• Eernisse, D. J., J. S. Albert, and F. E. Anderson. 1992. Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralian metazoan morphology. Systematic Biology 41:305-330.

• Janies, D. 2001. Phylogenetic relationships of extant echinoderm classes. Canadian Journal of Zoology 79:1232-1250.

• Martindale, M.Q., Finnerty, J.R. & J. Q. Henry. 2002. The Radiata and the evolutionary orginis of the bilaterian body plan. Molecular Phylogenetics & Evolution 24: 358-365.

• Meglitsch, P.A. & F.R. Schram. 1991. Invertebrate Zoology, 3rd Ed., Oxford.

• Nielsen, C. 2012. Animal Evolution. Interrelationships of the Living Phyla, 3rd Ed. Oxford.

• Pawlowski, J. 2015. Protist evolution and phylogeny. DOI: 10.1002/9780470015902.a0001935.pub2

• Pearse, V., J. Pearse, M. Buchsbaum & R. Buchsbaum. 1987. Living Invertebrates, Blackwell.

• Regier et al. 2010. Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences. Nature 463:1079-1084.

• Ruppert, E.E., R.S. Fox & R.D. Barnes. 2004. Invertebrate Zoology, 7th Ed, Thomson - Brooks/Cole.

• Sperling, E.A., Peterson, K.J. and D. Pisani. 2009. Phylogenetic-signal dissection of nuclear housekeeping genes supports the paraphyly of sponges and the monophyly of Eumetazoa. Molecular Biology & Evolution 26:2261-2274.

• Telford, M. J. 2008. Xenoturbellida: The fourth deuterostome phylum and the diet of worms. genesis 46:580-586.

• Torruella, G. et al. 2015. Phylogenomics reveals convergent evolution of lifestyles in close relatives of animals and fungi. Current Biology 25:2404-10.

• Wagele, J.-W. and B. Misof. 2001. On quality of evidence in phylogeny reconstruction: A reply to Zrzavy's defence of the 'Ecdysozoa' hypothesis. Journal of Zoological Systematics and Evolutionary Research 39: 165-176.

• the Porifera may be paraphyletic
• the Ctenophora may lie basal to the Cnidaria (or even the Porifera!)
• the Platyhelminthes may be paraphyletic (Acoelomorpha may lie outside the Protostomia)
• the Protostomia is split into two major clades: Spiralia (composed of two clades: lophophore bearing animals and animals having a trochophore larva) and the Ecdysozoa (clade of molting animals). However, support for the Ecdysozoa clade is based largely on DNA sequence data, and some papers using data from complete genome sequences do not support the Ecdysozoa clade:
  - 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. & R. Friedman. 2004. Shedding genomic ballast: Extensive parallel loss of ancestral gene families in animals. Journal of Molecular Evolution 59: 827-833.

• several aschelminth (pseudocoelomate) phyla may be placed in the Ecdysozoa or other phyla
• lophophorates may group with other protostomes in the Spiralia instead of in the Deuterostomia
• 'Uniramia' is likely polyphyletic (Myriapoda is sister to Crustacea+Hexapoda) and the Crustacea may be paraphyletic (Remipedia+Cephalocarida may be closer to Hexapoda than to other Crustacea; see alternative Panarthropoda molecular phylogeny)

  For another detailed consideration of phylogenetic relations that includes fossil taxa & references to original literature, see Mikko's Phylogeny Archive Page or the University of California Museum of Paleontology.

Some recent, accessible papers on molecular phylogenies for animal phyla include:

• Philippe et al. 2009. Phylogenomics revives traditional views on animal relations. Current Biology 19:706-12.
• Philippe et al. 2011. Resolving difficult phylogenetic questions: Why more sequences are not enough. PLoS Biology 9(3) e1000602.
• Schierwater et al. 2009. Concatenated analysis sheds light on early metazoan evolution and fuels a modern "Urmetazoon" hypothesis. PLoS Biology 7(1): e1000020. doi:10.1371/journal.pbio.1000020.

CONCLUSION: Experts disagree about which tree is closest to the 'true' phylogenetic tree of animal life, which means we have much yet to learn about how molecules and morphology evolve, and about which evidence provides more valuable clues. Beware trees that do not emphasize well-defined synapomorphies!

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