The Cretaceous is unrelated with Paleogene extinction event.
The Cretaceous -LRB- -LSB- pronkrᵻˈteɪʃəs -RSB- , -RRB- is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago -LRB- Mya -RRB- to the beginning of the Paleogene Period Mya .. geologic period and system. geologic period. Jurassic. Jurassic. Mya. annum. Paleogene. Paleogene. It is the last period of the Mesozoic Era .. Mesozoic Era. Mesozoic Era. The Cretaceous Period is usually abbreviated K , for its German translation Kreide -LRB- chalk -RRB- .. German. German language. The Cretaceous was a period with a relatively warm climate , resulting in high eustatic sea levels that created numerous shallow inland seas .. climate. climate. eustatic sea levels. Sea level#Local and eustatic. inland seas. Inland sea ( geology ). These oceans and seas were populated with now-extinct marine reptiles , ammonites and rudists , while dinosaurs continued to dominate on land .. extinct. extinct. ammonites. ammonites. rudists. rudists. During this time , new groups of mammals and birds , as well as flowering plants , appeared .. birds. birds. flowering plants. flowering plants. The Cretaceous ended with a large mass extinction , the Cretaceous -- Paleogene extinction event , in which many groups , including non-avian dinosaurs , pterosaurs and large marine reptiles died out .. Paleogene. Paleogene. mass extinction. mass extinction. The end of the Cretaceous is defined by the abrupt Cretaceous -- Paleogene boundary -LRB- K -- Pg boundary -RRB- , a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras .. Paleogene. Paleogene. mass extinction. mass extinction. Cenozoic. Cenozoic. eras. era ( geology )