The tertiary consisted of two main epochs. The Paleocene, the Eocene and the Oligocene, which make up the Paleogene; and the Miocene and Pliocene, which make up the Neogene. The close of the Cretaceous Period marked a major transition in Earth’s history. Ammonoids and marine reptiles disappeared from the sea. Marine taxa that persist as familiar inhabitants of modern ocean, among them bottom dwelling molluscs. On the land, the flowering plants of the Paleogene resembled those of latest Cretaceous time in many ways, but animal life changed dramatically. Taking the place of dinosaurs were the mammals, which were univ