Paleógeno

Paleógeno is the earliest of the three periods in the Cenozoic Era. It spans from 66 to 23 million years ago. The Paleogene Period is divided into three epochs: the Paleocene, Eocene, and Oligocene. This period began with the Cretaceous–Paleogene extinction event, which wiped out the non-avian dinosaurs, and marked the beginning of the age of mammals.

During the Paleocene, the Earth's climate began to warm. Continents continued to drift towards their present positions. Mammals, which were small and lived in the shadow of dinosaurs during the Mesozoic Era, began to diversify and increase in size and ecological dominance. Early primates, rodents, and ungulates appeared.

The Eocene was characterized by a generally warm climate, with global temperatures peaking in the early Eocene. This warmth facilitated the spread of forests across much of the globe. Mammalian evolution continued rapidly, with the diversification of many modern orders. Whales evolved from land-dwelling mammals, and birds also became more diverse.

The Oligocene saw a cooling trend and the development of more modern ecosystems. Grasslands began to expand, leading to the evolution of grazing mammals. Ice sheets began to form in Antarctica. The climate became more seasonal, and many modern plant and animal families became established. The Paleogene Period concluded with the start of the Neogene Period.