from 63 million to 58 million years ago; appearance of birds and earliest mammals

Earliest epoch of the Tertiary period, spanning the time between 65 and 55.5 million years ago. It is named after the Greek words "palaois" (old) and "ceno" (new).

See geologic time.

The first of five epochs in the Tertiary period, lasting from 66.4 to 57.8 Ma. It is preceded by the Late epoch of the Cretaceous period and followed by the Eocene epoch.

the earliest epoch of t he Tertiary period, before the Eocene, during which shallow inland seas drained and the first primates appeared. [AHDOS

The Paleocene, "early dawn of the recent", is a geologic epoch that lasted from 65.5 ± 0.3 Ma to 55.8 ± 0.2 Ma (million years ago). It is the first epoch of the Palaeogene Period in the modern Cenozoic era. As with most other older geologic periods, the strata that define the epoch's beginning and end are well identified but the exact date of the end is uncertain.