Proterozoic

Prot er o zo ic |ˌprōtərəˈzōik ˌproʊtərəˈzoʊɪk | ▶adjective Geology of, relating to, or denoting the eon that constitutes the later part of the Precambrian, between the Archean eon and the Cambrian period, in which the earliest forms of life evolved. • (as noun the Proterozoic ) the Proterozoic eon or the system of rocks deposited during it. The Proterozoic lasted from about 2,500 million to 570 million years ago. For millions of years only bacteria, algae, and other simple organisms existed, and the early invertebrates that followed were soft-bodied and rarely left any trace in the form of fossils. ORIGIN late 19th cent.: from Greek proteros ‘former ’ + zōē ‘life, ’ zōos ‘living ’ + -ic .

Proterozoic

Proterozoic |ˌprəʊt (ə )rəˈzəʊɪk | ▶adjective Geology relating to or denoting the aeon that constitutes the later part of the Precambrian, between the Archaean aeon and the Cambrian period, in which the earliest forms of life evolved. • (as noun the Proterozoic ) the Proterozoic aeon or the system of rocks deposited during it. The Proterozoic lasted from about 2,500 to 570 million years ago. For millions of years only bacteria and single-celled organisms existed, and the early invertebrates that followed were soft-bodied and rarely left any trace in the form of fossils. ORIGIN late 19th cent.: from Greek proteros ‘former ’ + zōē ‘life ’, zōos ‘living ’ + -ic .