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ZoomDinosaurs.com
The Mesozoic Era (248 - 65 million years ago) Ages of the Mesozoic Era
Triassic Period
248 - 206 mya
First dinosaurs and mammals
Jurassic Period
206-144 mya
Many dinosaurs and the first birds
Cretaceous Period
144-65 mya
First flowering plants, the height of the dinosaurs. Ends in huge extinction.
Early - Middle
248-227 mya
Late
227-206 mya
Early
(Lias)

206-180 mya
Middle
(Dogger)

180-154 mya
Late
(Malm)

154-144 mya
Early
(Neocomian)

144-127 mya
Middle
(Gallic)

127-89 mya
Late
(Senonian)

89-65 mya

THE CRETACEOUS PERIOD


THE CRETACEOUS PERIOD

The Cretaceous period was the heyday of the dinosaurs. Huge carnivores like Tyrannosaurus rex and Giganotosaurus appeared, as did Triceratops and many, many others. There was a tremendous diversity in dinosaur species. Mammals were flourishing, and flowering plants developed and radically changed the landscape.

The breakup of the supercontinent Pangaea into separate continents was underway. The separation of Laurasia and Gondwana was complete. In the first half of the Cretaceous, temperatures were warm, seasonality was low, and global sea levels were high (no polar ice!). At the end of the Cretaceous, there were severe climate changes, lowered sea levels, and high volcanic activity .

The Cretaceous period ended 65 million years ago with the extinction of the dinosaurs and many, many other prehistoric life forms. This mass extinction was the second-most extensive in the history of the Earth.

Creta is the Latin word for chalk. The Cretaceous period is named for chalky rock from southeastern England that was the first Cretaceous period sediment studied.



OTHER ANIMALS AND PLANTS IN THE CRETACEOUS
The first placental mammals appeared at the beginning of the Cretaceous. The Cretaceous saw the rise and extinction of the toothed birds, Hesperornis and Ichthyornis. The earliest fossils of birds resembling loons, grebes, cormorants, pelicans, flamingos, ibises, rails, and sandpipers were from the Cretaceous.

During the Cretaceous, primitive flowering plants (anthophytes, also called angiosperms) continued to develop (they evolved about 140 million years ago, during the late Jurassic period). Flowering plants (like magnolia, ficus, credneria, sassafras, viburnum) quickly outnumbered the other plants (mostly ferns , horsetails, trees (like conifers and gingkos), and cycads ), changing the environment tremendously. The extinction of bennettitaleans (a major group of plants) also occurred at this time.


GEOLOGY AND CLIMATE DURING THE CRETACEOUS
There was no polar ice during the mild warm, subtropical Cretaceous. The land was covered with forests surrounded by shallow seas. Seasonality was increasing.

Most of the land mass was at or around sea level until the mid-Cretaceous, a time of high tectonic activity (continental plate movement) and accompanying volcanic activity . This is when many mountain ranges were formed, including California's Sierra Nevadas, the Rocky Mountains in the western USA and the European Alps. The sea levels rose during the mid-Cretaceous, covering about one-third of the land area. Toward the end of the Cretaceous, there was a drop in sea level, causing land exposure on all continents, more seasonality, and greater extremes between equatorial and polar temperatures. Also, the continents were taking on their modern-day forms.



THE END OF THE CRETACEOUS AND THE END OF THE DINOSAURS

The Cretaceous period ended with a bang! About 65 million years ago, a mass extinction wiped out the dinosaurs (except for the birds) and many other animals, including pterosaurs , ichthyosaurs , ammonites, mosasaurs, plesiosaurs, and half of all invertebrate marine organisms. The primary cause of the Cretaceous-Tertiary extinction is thought to be an asteroid impact , but there are a lot of other theories, including high volcanism, climate changes due to continental drift, the effects of disease, and/or competition from egg-eating mammals . Although this extinction was huge, it was small when compared to the Permian-Triassic extinction (which preceded the existence of the dinosaurs).

The Age of Reptiles came to an end. The Age of Mammals was about to begin.

Printout:
Cretaceous animal printouts



ZoomDinosaurs.com
The Mesozoic Era (248 - 65 million years ago) Ages of the Mesozoic Era
Triassic Period
248 - 206 mya
First dinosaurs and mammals
Jurassic Period
206-144 mya
Many dinosaurs and the first birds
Cretaceous Period
144-65 mya
First flowering plants, the height of the dinosaurs. Ends in huge extinction.
Early - Middle
248-227 mya
Late
227-206 mya
Early
(Lias)

206-180 mya
Middle
(Dogger)

180-154 mya
Late
(Malm)

154-144 mya
Early
(Neocomian)

144-127 mya
Middle
(Gallic)

127-89 mya
Late
(Senonian)

89-65 mya



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