Proterozoic 元古宙
The Proterozoic (pronunciation: ) is a geological eon representing the time just before the proliferation of complex life on Earth. The name Proterozoic comes from Greek and means "earlier life",the Greek root protero-,means "former, earlier" and zoic-,means "animal, living being". The Proterozoic Eon extended from 7016788940000000000♠2500 Ma to 7016171042192000000♠542.0±1.0 Ma (million years ago), and is the most recent part of the Precambrian. It is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.