Hyracodon (Greek for "hyrax tooth"); pronounced hi-RACK-oh-don
Woodlands of North America
Middle Oligocene (30-25 million years ago)
Size and Weight:
About 5 feet long and 500 pounds
Horse-like build; three-toed feet; large head
Although Hyracodon looked a lot like a prehistoric horse--which were thick on the ground in Oligocene North America--an analysis of this creature's legs shows that it wasn't a particularly fast runner, and therefore probably spent most of its time in sheltered woodlands rather than open plains (where it would have been more susceptible to predation). In fact, Hyracodon is now believed to have been the earliest megafauna mammal on the evolutionary line leading to modern-day rhinoceroses (a journey that included some truly enormous intermediate forms, such as the 15-ton Indricotherium).