Paleogene Period

Diversification of flowering plants and mammals

The Paleogene Period (66–23 Ma) is in the Cenozoic Era, occurring after the Mesozoic Era, and before the Neogene Period.

Geologic Age

  • 66.023.03 million years ago


Eon / Era / Epoch

What happened during this time?


  • Climate cools during the middle to late Paleogene

  • Carbon dioxide levels begin around 900 ppm, increase to 1,000 ppm at the PETM, and then start to drop to 500 ppm by the end of the period

  • Oxygen levels start at 23% and hover around 21.5%, close to modern levels

  • Continents in similar geography to today



  • The Paleogene is a time of recovery from the Cretaceous extinction

  • Many extant modern plants arose during this time.

  • As the Earth cools and dries, many wet, tropical plants are replaced by coll-adapted, dry-adapted plants

  • Conifers, retreat to mountainous areas due to angiosperm competition


  • Animals recover from the Cretaceous extinction

  • This is the rise of mammals in which they begin to fill the niches left empty by dinosaur extinction

Additional Resources