| The Middle subperiod was marked by the Sui unification and their supplementation by the Tang, the Second Split, and the Song unification. |
| In the Pennsylvanian subperiod of the Carboniferous geological period, these rock layers were narrowed and folded as a result of the Variscan orogeny. |
| This sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. |
| Synapsida, a clade that contains mammals and their extinct relatives, originated during the Pennsylvanian subperiod, when they split from reptilian and avian lineages. |
| The first amniotes apparently arose in the Pennsylvanian subperiod of the Carboniferous. |
| There are three issues resulting from the geochronologic extension of fossil Holometabola to the Pennsylvanian-Mississippian Subperiod boundary or even earlier. |
