TAXA OF LIFE

MAJOR CLADES OF THE ANIMAL KINGDOM

This following figure is a modification of the summaries of Giribet et al. (2007) and Valentine (2004) in which the Animal Kingdom is monophyletic and forms four major clades: the CHOANOFLAGELLATES (CHOANOZOA), PARAZOA (Clade 2), RADIATA (Clade 4), and BILATERIA (Clade 5).   Here, the Bilateria is separated into the Deuterostomata (Clade 6) and the Protostomata (Clade 7).  The Protostomes are further divided into the Ecdysozoa (Clade 8), the Platyzoa (Clade 10), and the Lophotrochozoa (Clade 11).  

MAJOR CLADES OF THE ANIMAL KINGDOM

Clade 1: The Metazoa: Development from a blastula.  Simple life history with gametic meiosis.

Clade 2: The Parazoa at the tissue-level of organization.

Clade 3: Organisms at the organ-level of organization with determinate development and 2-3 tissue layers. 

Clade 4: The Radiata; diploblastic, usually with radial symmetry.

Clade 5: The Bilateria; triploblastic, usually bilaterally symmetrical.  Animal develops from a gastrula that forms a gut, mesoderm, and body cavity.

Clade 6: The Deuterostomes; the blastopore becomes the anus.

Clade 7: The Protostomes; the blastopore becomes the mouth.

Clade 8: The Ecdysozoa; the molting animals.

Clade 9: The Spiralia; the protostomes with spiral cleavage.

Clade 10: The Platyzoa; mostly animals in which the blastocoel becomes the body cavity, a pseudocoelom.

Clade 11: The Lophotrochozoa: animals that have a trochophore larva, some of which bear lophophores.

LITERATURE CITED

Giribet, G., C. W. Dunn, G. D. Edgecombe, and G. W. Rouse. 2007. A modern look at the Animal Tree of Life.  Zootaxa. 1668: 61-79. 

Valentine, J. W. 2004. The Origin of Phyla. University of Chicago Press. Chicago.  614 pp.

By Jack R. Holt.  Last revised: 12/25/2011