2020 Volume 60 Issue 2 Pages 269-278
In this article, the recent progress in molecular phylogenetics of placental mammals and eutherians was reviewed. It was established that the eutherians consisted of three major clades: Afrotheria, Xenarthra, and Boreotheria, which corresponded to Africa, South America, and the ancient northern continent, Laurasia. This finding suggested that vicariance due to the breakup of the supercontinent played an important role in the evolution of eutherians. Furthermore, the time-tree analyses of molecular data showed that oversea dispersals also played an important role. The recent accumulation of abundant genome data allowed us to infer not only the phylogeny but also the life history traits of common ancestors. An application of the new method detected a post K-Pg nocturnal bottleneck, where all ancestral lineages of extant eutherians were nocturnal just before the Eocene-Oligocene transition at 33.9 mya.
