proterozoic
/ˌprɑtərəˈzoʊɪk/
adjective
- Relating to the geological eon from about 2.5 billion to 541 million years ago, before the Paleozoic era.
- Fossils from the Proterozoic era are rare but very important to scientists.
- The Proterozoic eon saw the rise of oxygen in Earth's atmosphere.
- Proterozoic rocks contain some of the earliest evidence of complex life.
noun
- The Proterozoic eon, a division of geologic time before the Paleozoic.
- Geologists divide the Proterozoic into three major periods.
- The Proterozoic lasted for nearly two billion years.
- During the Proterozoic, the first multicellular organisms appeared.