How long did the Paleogene Period last?

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Cenozoic migration routes — Cenozoic Era Principal Cenozoic faunal migration routes and barriers.

The Paleogene Period lasted for 43 million years, spanning the interval from 66 million to 23 million years ago.123

As the oldest of the three stratigraphic divisions of the Cenozoic Era, it comprises three distinct epochs:
* Paleocene Epoch: 66 million to 56 million years ago13
* Eocene Epoch: 56 million to 33.9 million years ago13
* Oligocene Epoch: 33.9 million to 23 million years ago13

The term Paleogene, meaning "ancient-born," was established to categorize these early Cenozoic strata, which were formerly grouped within the now-obsolete Tertiary Period.123