Earliest Known Ancestor of Placental Mammals Discovered Earliest Known Ancestor of Placental Mammals Discovered Earliest Known Ancestor of Placental Mammals Discovered «Earliest Known Ancestor of Placental Mammals Discovered» «Earliest Known Ancestor of Placental Mammals Discovered» «Earliest Known Ancestor of Placental Mammals Discovered» Earliest Known Ancestor of Placental Mammals Discovered. 125 million of years of evolution at work Nationalgeographic: Eomaia Earliest Known Ancestor of Placental Mammals Discovered