This episode of Walking with Beasts features the largest land mammal ever, Paraceratherium, and other similarly extraordinary creatures of the Oligocene Epoch. Set in Mongolia, 25 Million Years Ago, the episode has an extremely rich source of fossil evidence in the form of the heavily fossil laden Hsanda Gol Formation. Discovered over a century ago, this Mongolia fossil site is a clear and thorough window into a world long lost. Climate change is continuing throughout the Oligocene, a process which began during the Eocene. It is noted that the plants and animals have adapted and are still adapting to the climate changes, with a recent example of the consequences of the changes taking their toll, being the end Eocene minor extinction event - in which 1 species in 5 perished.