The Paleogene

The Paleogene Period of the Cenozoic Era: 65.5 to 23.0 million years ago

The Paleogene is divided into three epochs, the Paleocene, Eocene, and Oligocene. During this relatively short span of time (about as long as the Triassic), the continents began to take on their present form. General cooling and drying began before the end of the Oligocene, but  was probably not a major factor until the middle Miocene. The Paleogene might be thought of as an extension of the Mesozoic -- but with mammals.

Walking With Prehistoric Beasts - DVD also in VHS - by the team that brought you Walking With Dinosaurs