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The Paleogene Period (IPA: / ˈ p eɪ l i. ə dʒ iː n,-l i. oʊ-, ˈ p æ l i-/ PAY-lee-ə-jeen, -lee-oh-, PAL-ee-; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 Ma (million years ago) to the beginning of the Neogene Period 23.04 Ma.
The Cretaceous–Paleogene (K–Pg) extinction event, [a] also known as the K–T extinction, [b] was the mass extinction of three-quarters of the plant and animal species on Earth [2] [3] approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs.
The date of the impact coincides precisely with the Cretaceous–Paleogene boundary (K–Pg boundary), slightly more than 66 million years ago. [7] The crater is estimated to be over 150 km (93 mi) in diameter [10] and 20 km (12 mi) in depth, well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out, widely thought to have been caused by the impact of a large asteroid that formed the Chicxulub crater in the Gulf of Mexico.
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk.
The stegosaurians appear to have gone extinct at some point in the late Early Cretaceous or early Late Cretaceous. A major change in the Early Cretaceous, which would be amplified in the Late Cretaceous, was the evolution of flowering plants. At the same time, several groups of dinosaurian herbivores evolved more sophisticated ways to orally ...
The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Cretaceous–Paleogene extinction event. The age ended , being followed by the Selandian. [5]
The Cenozoic began at the Cretaceous–Paleogene extinction event with a massive disruption of plant communities. It then became just as much the age of savannas, or the age of co-dependent flowering plants and insects. At 35 Ma, grasses evolved from among the angiosperms.