Before revision: O2 showed major variations until reaching a steady state of more than 15%DIF < by the end of the Precambrian,Christopher R. Scotese, Back to Earth History : Summary Chart for the Precambrian, Paleomar Project followed by an evolutionary radiation event known as the Avalon explosion, where complex metazoan life forms (including the earliest cnidarians, placozoans and bilaterians) first proliferated.
After revision: during the Proterozoic, including Boring Billion|a billion-year periodof euxinia,O2 showed major variations until reaching a steady state of more than 15%DIF < by the end of the Precambrian,Christopher R. Scotese, Back to Earth History : Summary Chart for the Precambrian, Paleomar Project followed by an evolutionary radiation event known as the Avalon explosion, where complex metazoan life forms (including the earliest cnidarians, placozoans and bilaterians) first proliferated.