About 50 million years ago at the beginning of the middle Eocene, Orohippus appeared. It was still of similar size and stature as Hyracotherium. Front limbs still ended in four, hind limbs in three toes. Over time, Orohippus' teeth showed some adaptation to a slightly coarser diet, including leaves and maybe some grasses. One of the premolars became more similar to a molar, providing more grinding surface.
During this time, the temperatures slowly started to decrease, which marked the onset of the transition in vegetation.