| Name | From | To | Age range |
|---|---|---|---|
| Alnus paleocordata | Late Miocene | Late Miocene |
|
| Alnus parva | Paleogene | Neogene |
|
| Alnus pentagona | Late Eocene | Late Eocene |
|
| Alnus pentaporina | Maastrichtian | Paleocene |
|
| Alnus percuriosa | Paleogene | Neogene |
|
| Alnus pigmaeus | Maastrichtian | Maastrichtian |
|
| Alnus polleminensis | Quaternary | Quaternary |
|
| Alnus praerhombifolia | Oligocene | Oligocene |
|
| Alnus pre-cordata | Late Paleocene | Early Pliocene |
|
| Alnus pre-japonica | Late Paleocene | Early Pliocene |
|
| Alnus precordata | Late Eocene | Late Eocene |
|
| Alnus principalis | Paleogene | Neogene |
|
| Alnus ptolemais | Late Neogene | Late Neogene |
|
| Alnus quadrangula | Middle Pliocene | Middle Pliocene |
|
| Alnus quadrapollenites | Late Cretaceous | Early Pliocene |
|
| Alnus quadriangula | Early Oligocene | Early Oligocene |
|
| Alnus quadropollenites | Eocene | Priabonian |
|