Ìgbà Ìbíniàtijọ́

Paleogene (ni ibomiiran, Palæogene, ni isale Ilẹ-ẹkọ giga) jẹ akoko ẹkọ-aye ati eto ti o bẹrẹ 65.5 ± 0.3 ti o pari 23.03 ± 0.05 milionu ọdun sẹyin o si ni apakan akọkọ ti Cenozoic Era.[1] Ọdun miliọnu 42 ti o pẹ, Paleogene jẹ ohun akiyesi pupọ julọ bi akoko eyiti awọn osin wa lati kekere diẹ, awọn fọọmu ti o rọrun sinu ẹgbẹ nla ti awọn ẹranko oniruuru ni ji ti iṣẹlẹ iparun Cretaceous–Tertiary ti o pari akoko Cretaceous ti o ṣaju. Diẹ ninu awọn ẹran-ọsin wọnyi yoo yipada si awọn fọọmu nla ti yoo jẹ gaba lori ilẹ, nigba ti awọn miiran yoo ni agbara lati gbe ni inu omi, ilẹ amọja ati paapaa awọn agbegbe afẹfẹ. Awọn ẹiyẹ tun wa ni riro lakoko yii, ti o yipada si awọn fọọmu ode oni aijọju. Pupọ julọ awọn ẹka igbesi aye miiran lori ilẹ ko yipada ni afiwe si awọn ẹiyẹ ati awọn ẹranko ni asiko yii. Diẹ ninu awọn continental išipopada mu ibi. Awọn oju-ọjọ tutu diẹ lori iye akoko Paleogene ati awọn okun inu ilẹ ti o pada sẹhin lati Ariwa America ni kutukutu akoko naa.

The Paleogene (alternatively Palæogene, informally Lower Tertiary) is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era.Formerly the period covered by the Paleogene was called the first part of the Tertiary, which usage is no longer official. "Whatever happened to the Tertiary and Quaternary?" Lasting 42 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Tertiary extinction event that ended the preceding Cretaceous Period. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial and even airborne environments.  Birds also evolved considerably during this period, changing into roughly modern forms.  Most other branches of life on earth remained relatively unchanged in comparison to birds and mammals during this period.  Some continental motion took place.  Climates cooled somewhat over the duration of the Paleogene and inland seas retreated from North America early in the period.

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