We meet Basilosaurus and Dorudon, two early species of whales. Although they have become completely adapted to life in the water, they still retain small hind legs that might have been used during mating. Global temperatures are still warm, and mammals are growing larger. The first elephants have appeared, including Moeritherium, which has adopted a lifestyle similar to that of modern hippos, preferring to spend its time in the water. Brontotherium, a large herbivore (plant eater) related to rhinos, tapirs and horses, moves in large herds across North America and Asia. Andrewsarchus, the largest terrestrial mammalian predator, is hunting the Brontotherium. Andrewsarchus looks like a canid (member of the dog family), but it is actually related to sheep, as can be seen by its hoofed feet. It was named after Roy Chapman Andrews, as he found specimens of it while prospecting in Mongolia in the 1920's. Apidium, a small primate originally thought to be an ungulate (hoofed mammal) was found during a 1907 expedition of the American Museum of Natural History in New York.
The next segment is set 24 million years ago, during the Early Oligocene Epoch (36 to 22.5 million years ago). The Indian subcontinent joins up with Asia. The ice cap at the South Pole has expanded, lowering sea levels. The tropical forests seen in the Early Eocene Period have retreated to the equatorial regions, and deciduous (broad-leafed trees) forests lie between the tropical regions and the poles. Grasses appear, and with them grazing animals. The animals in this segment are found in the Hsanda Gol Formation in Mongolia.
Solitary Indricotheres roam the plains. These giant relatives of the rhinos can reach over 20 feet tall and weigh 15 tons; they were the largest mammals ever to walk the earth. Hyaenodons, which are not really related to hyenas, attempt to prey on young Indricotheres. These predators possessed jaws and teeth capable of crushing bones, and could even eat teeth, as is shown in their coprolites. Amphicyonids, known as "bear dogs," ranged in size from small dog-like creatures to others that were close to the size of grizzly bears. Entelodonts, large, ill-tempered relatives of pigs, are also to be avoided, as they will fight with anyone. A Chalicothere, a herbivore similar in form to the giant sloths, is ambushed by a group of Hyaenodons.
