what era is the age of mammals
The Age Of Mammals Begins. The Tertiary Period marks the beginning of the Cenozoic Era. It began 65 million years ago and lasted more than 63 million years, until 1.8 million years ago. The Tertiary is made up of 5 epochs 1  : The Paleocene Epoch - 65 to 54 million years ago. 2  The Eocene Epoch - 54 to 38 million years ago.