The geological period following the Mesozoic (Secondary) era, constituting the first of two periods of the Cenozoic Era, the second being the Quaternary. It comprises the epochs Palaeocene, Eocene, Oligocene, Miocene, and Pliocene. It extended from the end of the Cretaceous to the beginning of the Quaternary, from 66.4-1.6 million years ago. The Miocene and Pliocene epochs were important in Hominid Evolution. Some prefer not to use the term Tertiary and instead divide the interval into two periods, the Paleogene Period (66.4-23.7 mya) and the Neogene Period (23.7-1.6 mya). Most of the existing mountain belts and ranges, notably the Andes, the Rockies, the Alps, the Himalayas, and the Atlas Mountains, were formed either partly or wholly during the Tertiary. The emergence and submergence of land bridges between continents, especially between North and South America, Eurasia and Africa, and Asia and North America, critically affected the migration of faunas and floras. The earliest generally accepted hominid fossils, those of Australopithecus, come from rocks of Pliocene age (5.3-1.6 mya) in eastern Africa.