The tree was reconstructed with a multidimensional vector space (MVS) method from 62 complete mt AA sequences [2]. The upper and lower half circles on the ancestral nodes and terminals represent the numbers of Hoa and Thr, respectively, relative to those of the root sequence. The decrease of Hoa and the increase of Thr were expressed by gradational changes from dark colors toward light ones of four grades (see the insertion). We defined the root sequence as the most recent common ancestor of Afrotheria and Xenarthra, and estimated the node sequences by applying the maximum parsimony algorithm to three groups of Hoa, Thr and Rma (the remaining AAs except for Hoa and Thr) (Materials and Methods).