High-level metazoan phylogeny is in a state of flux. This is a time of unparalleled research activity and funding possibilities. Reconstructing the tree of life has been afforded similar priority status as the various genome-sequencing projects. As a result, the next decade will witness a great expansion and refinement of our developing views about the phy-logenetic history of life. The overview presented in this article should thus be considered as merely a tentative sketch, parts of which will be consolidated as new data accrue, while other parts will inevitably be significantly altered. The mono-phyly of Protostomia, the phylogeny within Lophotrochozoa, and the sequence of divergences of nonbilaterians are some of the most pressing questions of high-level metazoan phylogenetics. However, similar unanswered questions also prevail on lower levels, ranging from the phylogeny of the basic gnathostome clades within the Vertebrata, to the phylogeny of extant birds. Irrespective of what the final topology of the animal tree of life will look like, we are certain to learn a lot in the next few years.
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