Miocene

American  

[mahy-uh-seen] / ˈmaɪ əˌsin /

adjective

1. noting or pertaining to an epoch of the Tertiary Period, occurring from 25 to 10 million years ago, when grazing mammals became widespread.

---

noun

1. the Miocene Epoch or Series.

Miocene British  

/ ˈmaɪəˌsiːn /

adjective

1. of, denoting, or formed in the fourth epoch of the Tertiary period, between the Oligocene and Pliocene epochs, which lasted for 19 million years

---

noun

1. this epoch or rock series

Miocene Scientific  

/ mī′ə-sēn′ /

1. The fourth epoch of the Tertiary Period, from about 24 to 5 million years ago. During this time the climate was warmer than it had been in the Oligocene, and kelp forests and grasslands first developed. With the isolation of Antarctica, a circumpolar ocean current was established in the southern Hemisphere, reducing the amount of mixing of cold polar water and warm equatorial water and causing a buildup of ice sheets in Antarctica. The African-Arabian plate became connected to Asia, closing the seaway which had previously separated Africa from Asia. Mammalian diversity was at its peak.

2. See Chart at geologic time

---

Other Word Forms

• post-Miocene adjective

Etymology

Origin of Miocene

First recorded in 1825–35; mio- (from Greek meíōn “less”) + -cene

Example Sentences

The oldest known chameleon fossils date to the early Miocene, about 16 to 23 million years ago, long after many of their arboreal adaptations had appeared.

From Science Daily

The Tatacoa Desert is home to rich deposits of fossils from an epoch known as the Middle Miocene.

From BBC

In a paper published January 2025, Reichgelt and collaborator Christopher West compared the shapes of fossil leaves of the Miocene gathered and analyzed in many previous studies with a dataset of modern leaf morphologies.

From Salon

The fossils dating to the Miocene were encased in a type of fossilized algae called diatomite.

From Los Angeles Times

Identifying how and why Antarctica's major ice sheets behaved the way they did in the early Miocene could help inform understanding of the sheets' behavior under a warming climate.

From Science Daily