A web-database of mammalian morphology and a reanalysis of placental phylogeny

Robert J Asher

doi:10.1186/1471-2148-7-108

Abstract

BackgroundRecent 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.ResultsThe 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 (Leptictis,Paleoparadoxia, Plesiorycteropus and Zalambdalestes) vary, highlighting the potential effect of sequence data on fossils for which such data are missing.ConclusionThe combined dataset supports the location of the placental mammal root at Afrotheria or Xenarthra, not at Erinaceus 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.

Highlights

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
(page number not for citation purposes) http://www.biomedcentral.com/1471-2148/7/108 including three fossils (Zalambdalestes, Ukhaatherium, and Centetodon) plus morphology (Fig. 3), places the placental root at Afrotheria followed by Xenarthra
Using a relatively large DNAindel-morphology dataset based on [8,9,17], this study has made a number of changes to both molecular and morphological homology, yet recovers the same basic pattern of living placental phylogeny (Figs. 1, 2, 3), dividing the unrooted tree into Afrotheria, Xenarthra, Euarchontoglires, and Laurasiatheria

Summary

Introduction

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. 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. Cladistic phylogeny reconstruction of mammals has its roots in publications by Malcolm McKenna [1] and was more explicitly algorithmic in the 1980s [2,3]. In the latter publications, discrete characters were analysed with an explicit optimality criterion, and were in principle observable by anyone with access to relevant material, in order to make specific, testable hypotheses regarding mammalian interrelationships. Calls for the improvement of standards by which morphological character data are published, and by which they are selected for inclusion in a given study, have been made [e.g., [6]]

Methods

Results

Conclusion