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For example, the Cretaceous–Paleogene extinction event, marks the lower boundary of the Paleogene System/Period and thus the boundary between the Cretaceous and Paleogene systems/periods. For divisions prior to the Cryogenian , arbitrary numeric boundary definitions ( Global Standard Stratigraphic Ages , GSSAs) are used to divide geologic time.
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.
c. 145 Ma – End of Jurassic and beginning of Cretaceous Period. c. 145 Ma – First mantises. c. 140 Ma – Earliest orb-weaver spiders evolve. c. 130 Ma – Laurasia and Gondwana begin to split apart as the Atlantic Ocean forms. First flowering plants. Earliest anglerfish. c. 125 Ma – Sinodelphys szalayi, the earliest known marsupial ...
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.
Badlands near Drumheller, Alberta, where erosion has exposed the Cretaceous–Paleogene boundary. The End Cretaceous extinction, or the K–Pg extinction (formerly K–T extinction) occurred at the Cretaceous (Maastrichtian) – Paleogene transition. [19] The event was formerly called the Cretaceous-Tertiary or K–T extinction or K–T ...
That is, Cretaceous and Paleogene squamates filled the same niches. Nonetheless, there was a faunal turnover of squamates, and groups that were dominant by the Eocene were not as abundant in the Cretaceous, namely the anguids , iguanas , night lizards , pythons , colubrids , boas , and worm lizards .
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.