PALEOGENE PERIOD: 65 to 23 million years ago

Paleocene Epoch: 65 to 56 million years ago

Eocene Epoch: 56 to 34 million years ago

Oligocene Epoch: 34 to 23 million years ago



During the Tertiary, the Atlantic and Indian Ocean basins expanded while that of the Pacific decreased. Australia separated from Antarctica. The Tethys Seaway was gradually lost as Africa and India collided with Europe and Asia. Mountain ranges (such as the Himalayas) formed as a result of these collisions. Italy collided with Europe to form the Alps. The Mediterranean (once part of the Tethys) was limited to the west as Africa approached Spain and closed to the East when Saudi Arabia fused with Asia. Great inland seas such as the Caspian and Aral Seas are remnants of the ancient Tethys seaway (Seyfert, 1979).

After the extinction of the dinosaurs, birds became the dominant predators in many areas on earth. As mammals diversified, these giant birds would only remain in isolated areas (such as South America). Ancestors of modern groups evolved such as early ducks and penguins.


At the beginning of the Cenozoic, the only mammals which existed were small, primitive forms. Prior to the diversification of placental mammals, marsupials evolved into many lineages which persisted in isolated continents (such as South America and Australia) with lineages as diverse as bear-sized predators and hippo-sized herbivores.


A number of extinct carnivorous mammal groups evolved which included the mesonychians (more closely related to modern herbivores than carnivorous mammals), creodonts, nimravid cats and bear dogs.


nimravidsbear dog

Whales evolved from four-footed semi-aquatic forms. By the Mid-Cenozoic, 20 meter whales which still retained vestigial hind legs were the top marine predators.


From primitive herbivores known as condylarths, small ancestral cloven-hoof mammals and small, multi-toed horses evolved.


From the earliest generalized primates evolved monkeys and subsequently the first apes.