The Pennsylvanian Period was from about 325 million to 280 million years ago. It is part of the Paleozoic Era. The Pennsylvanian and the Mississippian (345 to 325 MYA) are often grouped together as the Carboniferous Period.
The Tertiary Period (including the Pliocene, Miocene, Oligocene, Eocene, and Paleocene Epochs) lasted from about 65 million years ago to 1.8 million years ago. It is part of the Cenozoic Era, along...