Eocene landscape (56 to 34 million years ago). The second oldest of the five major worldwide divisions (epochs) of the Tertiary Period (Cenozoic Era), the interval of time (epoch) extending from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The diversification of life seen in the Paleocene continued in the Eocene, a reflection of the poleward expansion of the tropics, particularly during early Eocene time. Middle and late Eocene time witnessed the development of extensive endemic animal evolution. Bats, flying lemurs, creodont carnivores, artiodactyls (cloven-hoof mammals, such as cattle, deer, and camels) and perissodactyls (odd-toed, hoofed mammals, such as rhinoceroses and horses). Illustration originally captioned: "Brown Coal Forest 50 to 30 million years ago." Lignite, often referred to as brown coal, is a soft brown fuel with characteristics that put it somewhere between coal and peat. It is considered the lowest rank of coal; it is mined in Greece, Germany, Poland, Serbia, Russia, the United States, India, Australia and many other parts of Europe and it is used almost exclusively as a fuel for steam-electric power generation. Up to 50% of Greece's electricity and 25% of Germany's comes from lignite power plants.