At the end of this period, there was a mass extinction commonly referred to as the K/T (or Cretaceous/Tertiary) extinction. At this extinction event, many commonly recognized groups such as dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser known groups, died out.
The Maastrichtian is named after the Dutch city Maastricht.
|Lower/Early Cretaceous||Upper/Late Cretaceous|
| Berriasian | Valanginian | Hauterivian|
Barremian | Aptian | Albian
| Cenomanian | Turonian | Coniacian|
Santonian | Campanian | Maastrichtian