Paraceratherium is an extinct genus of gigantic hornless rhinoc-eros-like mammals endemic to Eurasia & Asia during the Oligocene epoch. It is regarded as the largest land mammal known, w/the largest species having an estimated mean adult mass of 12 tons.
The Pyrotheria are a group of extinct mammals that lived during the Eocene and Oligocene in South America and had some similarities with the elephants. But they were not related to this, but are counted to the South American ungulates.
The entolodont Archaeotherium scares away a pair of the primitive dog Hesperocyon from a watering hole. Oligocene of western North America. By Mauricio Anton from the book "National Geographic: Prehistoric Mammals"