| Summary: | <p>Abstract</p> <p>Background</p> <p>Recent publications concerning the interordinal phylogeny of placental mammals have converged on a common signal, consisting of four major radiations with some ambiguity regarding the placental root. The DNA data with which these relationships have been reconstructed are easily accessible from public databases; access to morphological characters is much more difficult. Here, I present a graphical web-database of morphological characters focusing on placental mammals, in tandem with a combined-data phylogenetic analysis of placental mammal phylogeny.</p> <p>Results</p> <p>The results reinforce the growing consensus regarding the extant placental mammal clades of Afrotheria, Xenarthra, Euarchontoglires, and Laurasiatheria. Unweighted parsimony applied to all DNA sequences and insertion-deletion (indel) characters of extant taxa alone support a placental root at murid rodents; combined with morphology this shifts to Afrotheria. Bayesian analyses of morphology, indels, and DNA support both a basal position for Afrotheria and the position of Cretaceous eutherians outside of crown Placentalia. Depending on treatment of third codon positions, the affinity of several fossils (<it>Leptictis</it>,<it>Paleoparadoxia</it>, <it>Plesiorycteropus </it>and <it>Zalambdalestes</it>) vary, highlighting the potential effect of sequence data on fossils for which such data are missing.</p> <p>Conclusion</p> <p>The combined dataset supports the location of the placental mammal root at Afrotheria or Xenarthra, not at <it>Erinaceus </it>or rodents. Even a small morphological dataset can have a marked influence on the location of the root in a combined-data analysis. Additional morphological data are desirable to better reconstruct the position of several fossil taxa; and the graphic-rich, web-based morphology data matrix presented here will make it easier to incorporate more taxa into a larger data matrix.</p>
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