The Thanetian (also known as the Landenian or Heersian) is the last stage of the Paleocene Epoch, corresponding to the Late Paleocene sub-epoch. It spans the time between 58.7 ± 0.2 Ma and 55.8 ± 0.2 Ma (million years ago). The name derives from the Thanet Beds, the oldest Paleocene deposits in the London Basin, named after the area of Kent known as the Isle of Thanet.
The Sézanne flora is a fossil assemblage preserved in freshwater limestone deposits at Sézanne, laid down during the Thanetian faunal stage, when Europe enjoyed a tropical climate. In the lagerstätte, leaves, entire flowers and seeds are minutely preserved.
|Paleocene epoch||Eocene epoch||Oligocene epoch|
| Danian | Selandian|
| Ypresian | Lutetian|
Bartonian | Priabonian
|Rupelian | Chattian|