Proterozoic

[ prot-er-uh-zoh-ik, proh-ter- ]

noun

1. the longest geologic eon and the most recent division of Precambrian time, during which the presence of oxygen in Earth’s atmosphere became significant, causing certain life forms to adapt to the use of oxygen and leading to a proliferation of complex multicellular life.

adjective

1. of or relating to this eon.

Proterozoic

/ ˌprəʊtərəʊˈzəʊɪk /

noun

1. See Archaeozoic
   the later of two divisions of the Precambrian era, during which the earliest plants and animals are assumed to have lived Compare Archaeozoic

adjective

1. of or formed in the late Precambrian era

Proterozoic

/ prŏt′ər-ə-zō′ĭk /

1. The later of the two divisions of the Precambrian Eon, from about 2.5 billion to 540 million years ago. The Proterozoic was characterized by the formation of stable continents, the appearance of abundant bacteria and archaea, and the buildup of oxygen in the atmosphere. By about 1.8 billion years ago the oxygen buildup was significant enough to cause many types of bacteria to die out. At this time eukaryotes, including multicellular algae and the first animals, first appear in the fossil record.
2. See Chart at geologic time

Word History and Origins

Origin of Proterozoic¹

First recorded in 1905–10; protero- + zo- + -ic

Example Sentences

Proterozoic , the age of invertebrate dominance, containing an early and a late ice age.

From Project Gutenberg

Proterozoic fossils have been found in places where the present average temperature approaches 0°C.

From Project Gutenberg

The recent discovery of glaciation in latitudes as low as 30° in the Proterozoic is correspondingly significant.

From Project Gutenberg

Hence, uplift alone cannot account for extensive glaciation in subtropical latitudes during the Permian and Proterozoic.

From Project Gutenberg

The late Proterozoic or very earliest Cambrian was probably the time of the great splitting up into groups.

From Project Gutenberg