Propalaeotherium, was a diminutive ancestor of the modern Horse, coming in two sub-species. One sub-species is around 30 cm maximum, the size of the average cat; and the other sub-species is up to around 55-65 cm long, still very tiny in comparison with the majestic stallions of today. Propalaeotherium, means, 'Before the Ancient Beast'.
Both forms stood no more than 1-2 feet tall, and would have been alert little foragers constantly watching out for danger. They were herbivores that fed on soft leaves and fruits. Propalaeotherium is part of a well charted evolution of the horse, and is one of the earliest known, bar one from being the earliest. It lived 50-45 Million Years Ago, living during the Early Eocene, in Europe.
A tiny mammal by our standards, Propalaeotherium was ironically actually rather large for its day, as the mean average size of mammals for its time as the size of a small shrew. Indeed, even today, this mean average is still only around rat sized. However, we have Elephant sized mammals, whereas during the day of Propalaeotherium, no such great megafaunal mammals existed at all. Propalaeotherium, being so ancient in the linneage of the Equines, hadn't even evolved hoofs. Instead, they had clawed 'hoof-like' toes. This animal would have been heavily reliant on acue sense to protect itself in the dangerous and weird forests of the Early Eocene. Giant Terror Bird, Gastornis, would have been a common predator of Propalaeotherium; needing to ambush such skittish and agile little horse ancestors.