Mitogenomic analyses of eutherian relationships.

Reasonably correct phylogenies are fundamental to the testing of evolutionary hypotheses. Here, we present phylogenetic findings based on analyses of 67 complete mammalian mitochondrial (mt) genomes. The analyses, irrespective of whether they were performed at the amino acid (aa) level or on nucleotides (nt) of first and second codon positions, placed Erinaceomorpha (hedgehogs and their kin) as the sister group of remaining eutherians. Thus, the analyses separated Erinaceomorpha from other traditional lipotyphlans (e.g., tenrecs, moles, and shrews), making traditional Lipotyphla polyphyletic. Both the aa and nt data sets identified the two order-rich eutherian clades, the Cetferungulata (comprising Pholidota, Carnivora, Perissodactyla, Artiodactyla, and Cetacea) and the African clade (Tenrecomorpha, Macroscelidea, Tubulidentata, Hyracoidea, Proboscidea, and Sirenia). The study corroborated recent findings that have identified a sister-group relationship between Anthropoidea and Dermoptera (flying lemurs), thereby making our own order, Primates, a paraphyletic assembly. Molecular estimates using paleontologically well-established calibration points, placed the origin of most eutherian orders in Cretaceous times, 70-100 million years before present (MYBP). The same estimates place all primate divergences much earlier than traditionally believed. For example, the divergence between Homo and Pan is estimated to have taken place approximately 10 MYBP, a dating consistent with recent findings in primate paleontology.