The Scenario

This scene depicts late spring in the Northern Great Plains about 10 million years ago, in what is now southern South Dakota. The Black Hills appear in the background, and a shallow stream with braided sandbars winds through the foreground. The water in the stream is deep enough to support a group of beavers. Grasses, shrubs, and trees growing along the streamside provide ample cover for a wolf-size carnivore, distantly related to modern dogs, to stalk the beavers and horses drinking from the stream.

The Environment

Trees were concentrated along the stream border, while further away, more open spaces had a lighter covering of shrubs, brush, and grasses. The climate was temperate with fairly mild winters, during which the temperature rarely fell below freezing and snow was quite unusual. Summers were hot and dry except for occasional thundershowers. At this time of year, water was sparse away from the stream, and stream-flow diminished to form waterholes frequented by most members of the local fauna. While the climate was drier, and the annual range of temperatures was narrower than in the same area today, the seasonal extremes were greater than in the Oligocene.