A Jurassic eutherian mammal and divergence of marsupials and placentals

Almost all living mammals are placentals. A key event in mammalian evolution was the divergence between the ancestors of today's placentals and those of the marsupials. The discovery of a fossil on the placental side of the split takes that divergence back 35 million years, to around 160 million years ago, deep into the Jurassic period. The fossil, from China, shows that the earliest members of the group that includes ourselves and most familiar mammals was a small creature adapted for climbing and scampering among the trees, presumably keeping well clear of the dinosaurs below. The age of the fossil suggests that there was a higher rate of mammal evolution in the Jurassic than previously believed.