Pliocene
The world continued to get cooler and drier in the Pliocene. Tropical rain forests and deciduous forests shrank. Grasslands grew, and many herbivorous mammals became grazers instead of browsers. Of this we are certain, because their teeth tell us what kind of food they ate. Browsers eat leaves and small branches, and grazers eat grass. The concept of mesowear deals with this. Mesowear is a method based on animals' tooth wear fingerprints. Each animal has special feeding habits, which cause unique tooth wear. Rough feeds cause serious tooth abrasion, while smooth one triggers moderate abrasion. So browsers have teeth with moderate abrasion and grazers have teeth with rough abrasion. Seeing the teeth of browsers next to those of grazers is convincing.