Usually we have Horse fossils from Oligocene to Pleistocene and some Holocene occasionally from Roman deposits in Europe. The earliest known member of the family Equidae was the Hyracotherium, which lived between 45 and 55 million years ago, during the Eocene period. It had 4 toes on each front foot, and 3 toes on each back foot. The extra toe on the front feet soon disappeared with the Mesohippus, which lived 32 to 37 million years ago. Over time, the extra side toes shrank in size until they vanished. All that remains of them in modern horses is a set of small vestigial bones on the leg below the knee, known informally as splint bones. Their legs also lengthened as their toes disappeared until they were a hoofed animal capable of running at great speed. By about 5 million years ago, the modern Equus had evolved.
Reindeer & Red Deer Fossils Rangifer tarandus & Cervus elaphus