1. The first period of the Cenozoic Era, lasting from approximately 66 to 23 million years ago, characterized by the diversification of mammals following the extinction of dinosaurs.
Usage: geology; capitalized; also called the Paleocene, Eocene, and Oligocene epochs collectively

1. Of, relating to, or denoting the Paleogene period or its rocks and fossils.
Usage: geology; capitalized

Examples

• The Paleogene period saw the rapid evolution of early primates and ungulates.
• Paleogene rocks in this region contain abundant fossils of extinct mammals.
• Scientists study Paleogene deposits to understand how life recovered after the dinosaur extinction.
• The climate during the Paleogene was generally warmer than today.
• Paleogene sediments reveal the transition from the Mesozoic to the modern world.