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.

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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

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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

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Other Word Forms

Derived Forms

• post-Miocene
  adjective

Etymology

Origin of Miocene

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

Example Sentences

We can pinpoint this re-evolution to the Miocene period, when Australia’s climate was becoming drier.

From Science Daily • May 21, 2026

Scientists previously assumed that ancient anacondas would have been even larger than modern ones because snakes are highly sensitive to temperature and the Miocene climate was warmer.

From Science Daily • Dec. 3, 2025

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

From BBC • Jul. 22, 2025

"We are currently not in the best case scenario, but also not the worst case scenario, we’re sort of on a middle trajectory, and that is what the Miocene best represents."

From Salon • Feb. 17, 2025

All had died from some mysterious cataclysm just under twelve million years ago in the time known to geology as the Miocene.

From "A Short History of Nearly Everything" by Bill Bryson