= Pennsylvanian
{c}
The <Pennsylvanian> is the later subperiod of the <Carboniferous>, following the <Mississippian> and preceding the <Permian>. It spans roughly 323 to 299 million years ago. The corresponding rocks form the <Pennsylvanian> subsystem: a time interval and the rocks deposited during it are related but distinct uses of the name.<International Chronostratigraphic Chart by International Commission on Stratigraphy (2026-06)>[Carboniferous subdivision and boundary ages]{ref}
The word is useful when comparing <fossils> from different regions. A <fossil> described as <Pennsylvanian> belongs to this interval rather than to an undifferentiated stretch of the <Carboniferous>. The classification provides a shared temporal framework; it does not imply that every locality had the same environment or preserved the same <organisms>.
Back to article page
