The first period of the Cenozoic Era (after the Cretaceous of the Mesozoic Era and before the Quaternary), thought to have covered the span of time between 65 million years and 3 to 2 million years ago. It is divided into five epochs: the Paleocene, Eocene, Oligocene, Miocene, and Pliocene. It was originally designated an era rather than a period; in this sense, it may be considered to have either five periods (Paleocene, Eocene, Oligocene, Miocene, Pliocene) or two (Paleogene and Neogene), with the Pleistocene and Holocene included in the Neogene.