Eocene
/ˈiːəʊsiːn/adjective
1- Geology of, relating to, or denoting the second epoch of the Tertiary period, between the Palaeocene and Oligocene epochs【地质】（与）始新世（有关）的。
1.1
- as noun the Eocene the Eocene epoch or the system of rocks deposited during it始新世; 始新世岩石。
The Eocene epoch lasted from 56.5 to 35.4 million years ago. It was a time of rising temperatures, and there was an abundance of mammals, including the first horses, bats, and whales.
词源
mid 19th cent.: from Greek ēōs 'dawn' + kainos 'new'.