Fig. 1.

—Phylogenetic tree of 28 vertebrate species. The tree topology is from Takezaki and Nishihara (2017). The branch lengths were estimated by the maximum likelihood method for each of 24 partitions obtained by PartitionFinder with BIC criterion and weighted averages were taken by excluding four partitions in which a single species had a long terminal branch (see Materials and Methods). Cartilaginous fish was used as outgroup. The numbers that follows N (N29–N54) are those given to internal nodes. The red circles indicate the three nodes used as calibration points in this study.