Maastrichtian

The Maastrichtian is the last age or stage of the Late Cretaceous epoch, spanning roughly from 72 to 66 million years ago. It follows the Campanian and precedes the Paleogene Danian, ending with the Cretaceous–Paleogene extinction event that wiped out many terrestrial and marine groups, including most non-avian dinosaurs.

The term Maastrichtian is derived from Maastricht, a city in the Netherlands, where rocks of this age were first studied and described. In the International Commission on Stratigraphy framework, the base of the Maastrichtian is defined by global stratigraphic markers within the Late Cretaceous, and its top coincides with the Cretaceous–Paleogene boundary. Regional stratigraphy often subdivides the Maastrichtian into lower and upper portions based on fossil content and lithology.

Climate during the Maastrichtian was generally warm, with relatively high sea levels producing widespread shallow seas in some regions. The fossil record shows continued dinosaur diversity up to the end of the period, including large theropods, hadrosaurs, and ceratopsians in suitable regions, many of which were eliminated at the K–Pg boundary. Marine life included mosasaurs and a variety of marine invertebrates, with ammonites and other groups providing key biostratigraphic signals. The flora saw the continued diversification of flowering plants, contributing to significant ecological shifts in many ecosystems.

Significance of the Maastrichtian lies in its role as the final stage of the dinosaur era, marking the transition to the Paleogene and shaping our understanding of late Cretaceous biogeography, climate patterns, and the events surrounding the mass extinction at the end of the Cretaceous.