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The Cenozoic Era ( or ; also Cænozoic, Caenozoic or Cainozoic or ;〔Oxford English Dictionary Second Edition, 1989.〕 meaning "new life", from Greek ''kainos'' "new", and ''zoe'' "life"〔(【引用サイトリンク】url=http://www.etymonline.com/index.php?term=Cenozoic&allowed_in_frame=0 )〕) is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the period from 65 million years ago to present day. The Cenozoic is also known as the Age of Mammals, because the extinction of many groups allowed mammals to greatly diversify. 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 large reptiles that had dominated during the Mesozoic. Some flightless birds grew larger than the average human. 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. Climate-wise, the Earth had begun a drying and cooling trend, culminating in the glaciations of the Pleistocene Epoch, and partially offset by the Paleocene-Eocene Thermal Maximum. The continents also began looking roughly familiar at this time and moved into their current positions. ==Subdivisions== The Cenozoic is divided into three periods: The Paleogene, Neogene, and Quaternary; and seven epochs: The Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene. The Quaternary Period was officially recognized by the International Commission on Stratigraphy in June 2009, and the former Tertiary Period was officially disused in 2004 because of the necessity to divide the Cenozoic into periods more like that of the previous Paleozoic and Mesozoic eras.〔(International Stratigraphic Chart )〕 The common use of epochs during the Cenozoic helps paleontologists better organize and group the many significant events that occurred during this comparatively short interval of time. There is also more detailed knowledge of this era than any other because of the relatively young strata associated with it. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cenozoic」の詳細全文を読む スポンサード リンク
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