On the International Chronostratigraphic Chart (v2024/12), the Paleozoic spans 538.8 to 251.902 million years before present.
base of the unit x base of the next younger unit -> spanA span is not stated anywhere on the chart: the chart gives boundary ages, and the span between two of them is composed from the two lines the premises cite.
- definition basis: International Chronostratigraphic Chart v2024/12; the chronostratigraphic counterpart of the Paleozoic is the Paleozoic Erathem.
- precision note: The chart states that numerical ages are subject to ongoing revision and do not define units; GSSPs do.
Evidence support: Derived from the cited evidence one source
Evidence: Cohen 2024 Primary authority