The major discordance between the two types of data concerns the rooting of the bilaterians, and the bilaterian sister-taxon.
Furthermore, neither brachiopods nor chaetognaths group with deuterostomes brachiopods are allied with the molluscs and annelids (Lophotrochozoa), whereas chaetognaths are allied with the ecdysozoans. Both types of data agree that arthropods are not closely related to annelids: the former group with nematodes and other molting animals (Ecdysozoa), and the latter group with molluscs and other taxa with spiral cleavage. Thus, we set out to explore animal phylogeny by analyzing with maximum parsimony 138 morphological characters from 40 metazoan groups, and 304 18S rDNA sequences, both separately and together.
Insight into the origin and early evolution of the animal phyla requires an understanding of how animal groups are related to one another.
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