Before revision: Paleozoic Era The Paleozoic era spanned roughly (Ma) and is subdivided into six geologic periods ; from oldest to youngest, they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.
After revision: Paleozoic Era The Paleozoic era spanned roughly (Ma) and is subdivided into six geologic periods : from oldest to youngest, they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.