Palaeocene

After a cooler start, the climate grew warmer during the epoch, far warmer than today, and the world was heavily forested. There were no ice caps at the poles. Warm seas circulated throughout the world, including the poles. The earliest Paleocene featured a low diversity and abundance of marine life, but this trend reversed later in the epoch.^[1] Tropical conditions gave rise to abundant marine life, including coral reefs. With the extinction of marine reptiles at the end of the Cretaceous, sharks became the top predators. At the end of the Cretaceous, the ammonites and many species of foraminifera became extinct.

Marine faunas also came to look like modern faunas. Only the marine mammals and an important family of sharks, the Carcharhinidae, are missing.

Non-avian dinosaurs may have survived to some extent into the early Danian stage of the Paleocene Epoch about 66 mya. The controversial evidence for such is a hadrosaur leg bone found from Paleocene strata in New Mexico;^[2] but such stray late forms may be derived fossils.^[3] This means they were fossilised, then erosion uncovered them, then they were buried again in a younger layer of rocks.

The warm Paleocene climate, much like that of the Cretaceous, supported polar forests. Rainfall is a major factor in plant diversity nearer the equator, but polar plants have to adapt to light (polar nights and midnight suns) and temperature. Because of this, plants from both poles evolved some similar characteristics, such as broad leaves. Plant diversity at both poles increased throughout the Paleocene, especially at the end, with the increasing global temperature.^[4]

The Palaeocene is divided into three stages:^[5]