Cretaceous

Cretaceous Period 145–66 million years aby PreЄ Є O S D C P T J K Pg N
Mean atmospheric O 2 content ower period duration	c. 30 vol % (150 % o modren level)
Mean atmospheric CO 2 content ower period duration	c. 1700 ppm (6 times pre-industrial level)
Mean surface temperatur ower period duration	c. 18 °C (4 °C abuin modren level)

The Cretaceous is a geologic period an seestem that spans 79 million years frae the end o the Jurassic Period 145 million years ago (Mya) tae the beginnin o the Paleogene Period 66 Mya. It is the last period o the Mesozoic Era, an the langest period o the Phanerozoic Eon. The Cretaceous Period is uisually abbreviatit K, for its German translation Kreide (cauk, creta in Laitin).

The Cretaceous wis a period wi a relatively wairm climate, resultin in heich eustatic sea levels that creatit numerous shallae inland seas. Thir oceans an seas war populatit wi now-extinct marine reptiles, ammonites an rudists, while dinosaurs conteena'd tae dominate on laund. In this time, new groups o mammals an birds, as weel as flouerin plants, appeared.

The Cretaceous (alang wi the Mesozoic) endit wi the Cretaceous–Paleogene extinction event, a muckle mass extinction in that mony groups, includin non-avian dinosaurs, pterosaurs an muckle marine reptiles dee'd oot. The end o the Cretaceous is defined bi the abrupt Cretaceous–Paleogene boondary (K–Pg boondary), a geologic seegnatur associatit wi the mass extinction that lies atween the Mesozoic an Cenozoic eras.