PALEOCENE

Paleocene, Paleocene epoch

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

Source: WordNet® 3.1

Etymology

Adjective

Paleocene (not comparable)

(geology) Of or pertaining to the Paleocene epoch.

Proper noun

Paleocene

(geology) A geologic epoch within the Paleogene period from about 65 to 56 million years ago; marked by the rise of the first large mammals in a tropical climate.

Usage notes

Also designated by the symbol P_ε.

Source: Wiktionary