Eurohippus and modern horse. Artwork comparing two mature Eurohippus (lower left) from 42 million years ago to an adult modern horse (Equus ferus caballus). Eurohippus was only some 50 centimetres long and a few kilograms in weight, while the modern horse nearly 2 metres tall at the shoulder, and weighs nearly half a ton. An ancient ancestor to modern horses, donkeys, and zebras, Eurohippus was about the size of a small dog and possessed three toes instead of a single hoof. Modern equines are adapted to the varying and sometimes harsh climates of grasslands. Eurohippus lived and foraged in the relative comfort of warm and moist forests.