<Tr> <Td_colspan="2"> Events of the Cenozoic view discuss edit - 70---- - 60---- - 50---- - 40---- - 30---- - 20---- - 10---- 0--Mesozoic Paleogene Neogene Quaternary n o z o i Phanerozoic An approximate timescale of key Cenozoic events . Axis scale: millions of years before present . </Td> </Tr> <P> The Cenozoic Era (/ ˌsiːnəˈzoʊɪk, ˌsɛ - /; also Cænozoic, Caenozoic or Cainozoic / ˌkaɪnəˈzoʊɪk, ˌkeɪ - /; meaning "new life", from Greek καινός kainós "new", and ζωή zōḗ "life") is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the period from 66 million years ago to the present day . </P> <P> The Cenozoic is also known as the Age of Mammals, because of the large mammals that dominated, such as Entelodon (a so - called "hell pig"), Paraceratherium (a hornless rhinoceros relative) and Basilosaurus (an early whale - despite the "- saurus" misnomer). The extinction of many large diapsid groups such as non-avian dinosaurs, Plesiosauria and Pterosauria allowed the mammals and birds to greatly diversify and become the world's predominant fauna . </P> <P> Early in the Cenozoic, following the K - Pg event, the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians . From a geological perspective, it did not take long for mammals and birds to greatly diversify in the absence of the dinosaurs that had dominated during the Mesozoic . Some flightless birds grew larger than humans . These species are sometimes referred to as "terror birds," and were formidable predators . Mammals came to occupy almost every available niche (both marine and terrestrial), and some also grew very large, attaining sizes not seen in most of today's terrestrial mammals . </P>

When did the cenozoic era begin and end