Eocene

A geological period division, the second to first when the Paleogene of the Cenozoic Era is divided into three periods. It refers to the period from approximately 56 million years ago to 33.9 million years ago. The strata formed during the Eocene are called the Eocene series. The climate was significantly warmer than today, and sea levels were high. In the animal kingdom, the ancestors of horses and elephants appeared in mammals, and large mammals also appeared. However, there are still very few animal species that are common to modern mammals. In the plant kingdom, maples, beeches, palms, and other trees increased in number.

[Toshiyuki Yamaguchi August 19, 2015]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

地質時代の時代区分の一つで、新生代の古第三紀を三つに分けたときの初めから2番目の時期。およそ5600万年前から3390万年前までの時代をいう。始新世に形成された地層を始新統という。気候は現在よりも著しく温暖で、高海面期にあたる。動物界の哺乳(ほにゅう)類ではウマやゾウの祖先型が出現し、大形のものも現れた。しかし、現在と共通する動物の種はまだきわめて少ない。植物界ではカエデ、ブナ、ヤシなどが増加した。

［山口寿之　2015年8月19日］

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