The Tertiary period is known as the age of mammals. This period begins 65 million years ago and extends to 2 million years ago. During the tertiary period the continents have already started to break up and many new life forms develop.
The first epoch in the Tertiary period is the Paleocene (meaning ancient recent life). The Paleocene epoch began 65 million years ago. By this time over 75% of all life on earth including the giant dinosaurs were eradicated from the face of the earth. This mass extinction left room for the few animals that survived the catastrophe. Mammals, which had been living in the dinosaur's shadow, began to evolve and rapidly spread throughout the world. The mammals were puny creatures with none exceeding the size of a small modern day bear. All were short-legged and plantigrade, with slim heads and small brain cavities. The majority of the earth's climate was tropical and sub-tropical. This warm climate allowed widespread development of angiosperms and large, flightless birds began to appear.
After the Paleocene epoch is the Eocene epoch. Eocene means Dawn of Recent Life. This epoch began 58 million years ago and spanned a 16 million year period. During this epoch many paleogeographic changes occurred in the world. The expansion of the mid-Atlantic ridge caused Greenland and Scandinavia to break apart forming the Norwegian-Greenland Sea. Due to this expansion a connection was made with the Atlantic Ocean and the Polar Regions which cooled the oceans a few degrees. Sea-level also rose and seas invaded much of Africa, Australia, and Siberia. The climate of the earth was generally warm, with tropical and sub-tropical areas. Tropical palms flourished as far north as the London Basin. Any changes in the vegetation were limited to the migration of types of plants in response to climate changes. Mammals were still radiating into many different forms. Small horses like the Hyracotherium, were common. Early elephants and rhinoceroses appeared. Among the mammals, Rodents became the dominant small mammals. Many different birds that were beginning to evolve include geese, ducks, herons, owls, and hawks. Whales are also appearing in this epoch. A few continents like Africa were separated on all four sides by the ocean and therefor almost completely cut of from the world. The allowed unique fauna to develop in isolation from the world.
The third epoch in the Tertiary epoch was the Oligocene, which began approximately 37 million years ago and spanned roughly for a 13 million-year period. There was a drastic increase in volcanic activity and plate tectonics. The supercontinent Gondwanaland broke up as Australia and South America separated both separated from Antarctica. India collided with Asia forming the Himalayan Mountain range. The overall climate begins to cool and tropical areas were giving way to more temperate grasslands and woodlands. Glaciers began to form in Antarctica, lowering the sea level. Angiosperms are highly dispersed and the vegetation of higher latitudes in the Northern Hemisphere changed from the broad-leaved tropical evergreen forest to a temperate deciduous woodland of evergreen and broad-leaved trees. Following the terminal extinction in the Eocene epoch. New kinds of mammals evolved and expanded into the prehistoric ancestors of dogs, cats, rhinoceroses, and horses.
