from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Of or relating to the later of the two divisions of Precambrian time, from approximately 2.5 billion to 570 million years ago, marked by the buildup of oxygen and the appearance of the first multicellular eukaryotic life forms. See Table at geologic time.
  • n. The Proterozoic Eon.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Of, or relating to the geologic eon from about 2,500 to 570 million years ago; comprises the Paleoproterozoic, Mesoproterozoic and Neoproterozoic eras; marked by the build up of oxygen in the atmosphere and the emergence of primitive multicellular life.
  • proper n. The Proterozoic eon.

from The Century Dictionary and Cyclopedia

  • Of or pertaining to the life existing before the time of the Cambrian or first fossils: a term originally proposed as a substitute for Azoic, Eozoic, Archæan, etc., in order to avoid the assertions contained in these words if taken literally.
  • n. The time during which the simplest life-forms were developed: applied to the interval between the Archeozoic and Paleozoic as used by Chamberlin and Salisbury. It is assumed that life existed, but no determinable forms have yet been found. The subdivisions of the Proterozoic are Keweenawan, Animikean, and Huronian.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. from 2,500 to 544 million years ago; bacteria and fungi; primitive multicellular organisms
  • adj. formed in the later of two divisions of the Precambrian era


from The American Heritage® Dictionary of the English Language, 4th Edition

Greek proteros, earlier, former; + -zoic.


  • The assembly and regulatory diversification of the genetic toolkit for animal development undoubtedly underpin Proterozoic and Cambrian evolution …


  • Late Proterozoic, so let's say 1,000 to 542.0 million years ago.

    Of Books and the Sea

  • Eukaryotic one-celled organisms became dominant in the Proterozoic Eon.

    Geologic time

  • We parked and spent the afternoon on the rocky beaches, surrounded by high granite cliffs (an unnamed granite formation dating from the Late Proterozoic), searching for bits of beach glass.

    "We've been watching you with all our eyes..."

  • In amongst the wildly contorted Proterozoic strata, we spotted small fish, an assortment of hermit crabs (Pagurus spp.), small spider crabs (Libinia spp.), and a number of different taxa of cancroids, including juvenile Rock crabs (Cancer irroratus).

    "Here, by the ocean, the sky's filled with leaves..."

  • Knoll and Carroll think there was a mass extinction event at the Proterozoic-Cambrian border.


  • This in turn surrounds less common remnants of Proterozoic sediments.

    Australian Fossil Mammal Sites, Australia

  • The fossil record shows that the first eukaryotic life appeared on Earth at the beginning of the Proterozoic aeon, about two gigayears ago, when the Earth was only about half its present age.

    George’s Cosmic Treasure Hunt

  • A complex of Silurian and Carboniferous volcanics and intrusives with Mesoproterozoic serpententites and ultramafics border Proterozoic rocks to the northwest and the McBride basalt to the north.

    Einasleigh upland savanna

  • Proterozoic rocks found to the west of the McBride basalt are some of the only parts of eastern Australia that remained above sea level during the Cretaceous period.

    Einasleigh upland savanna


Log in or sign up to get involved in the conversation. It's quick and easy.