MesozoicCenozoic

MesozoicCenozoic is not a formal term in the current geologic timescale, but it may be used to refer collectively to the Mesozoic and Cenozoic eras, the two most recent major intervals of Earth’s history after the Paleozoic. This combined reference highlights a lengthy span during which complex life, fossils, and climate underwent significant changes, culminating in the rich diversity of mammals and flowering plants seen today.

The Mesozoic era, lasting from about 252 to 66 million years ago, is divided into the Triassic, Jurassic, and Cretaceous periods. It is known for the dominance of dinosaurs and the evolution of the first true crocodilians, pterosaurs, and early birds, as well as the diversification of marine reptiles. Gymnosperms and later angiosperms became prominent, and the supercontinent Pangaea gradually broke apart. The era ended with the Cretaceous-Paleogene boundary, marked by a mass extinction that affected non-avian dinosaurs and many marine groups, likely caused by an asteroid impact and volcanic activity.

The Cenozoic era, from about 66 million years ago to the present, includes the Paleogene, Neogene, and Quaternary periods. It features rapid mammalian and avian diversification, the rise of most modern plant groups, and climatic shifts toward cooler, more variable conditions. The Neogene saw further faunal evolution and the appearance of many modern mammal lineages, while the Quaternary is characterized by repeated ice ages and the emergence of Homo sapiens in the late Pleistocene and Holocene epochs.

In practice, MesozoicCenozoic serves as a shorthand for discussing the broad late-Paleozoic to present Earth history, rather than as a formal timescale term.