Era
From EvoWiki
An era is the second largest subdivision of geologic time, being longer than a period, but shorter than an eon. Earth's history is typically divided into five such eras. Starting from the current and working backwards, they consist of the Cenozoic, Mesozoic, Paleozoic, Proterozoic and Archaean.
See also: Geological timescale and History of the Earth‎.

