These fossils are from a time called the Oligocene Epoch. The Oligocene extended from about 32 million years ago until 23 million years ago.
This was about the time that the finishing touches were being put on Wind Cave. Visitors to the place we call Wind Cave National Park would have seen a very different world.
The Great Plains Provide Habitat
The Great Plains were just beginning to develop. Dense woodlands were giving way to wooded grasslands. The climate became cooler and drier for a long period transforming the vegetation of the Earth to something far more like that of today. These changing environments had a dramatic effect on the lives of mammals around the world.
Time of the Mammals
Mammals, which blossomed with the disappearance of the dinosaurs, were expanding both in range and variety as land bridges between the continents allowed them to invade new territory. Here in South Dakota the Great Plains was a rich environment where many animals, ones we would identify as quite unusual, lived their lives. The first teeth noticed at the site were those of a Subhyracodon - a cow-sized rhinoceros. Another animal found was a Mesohippus - a greyhound-sized horse.
For more information about the Centennial Site click on the links below.