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The end of the Cretaceous Period is marked
by another mass extinction. It is the second most devastating extinction after the one at the end of the Permian Period. It marks the end of the Mesozoic Era. About half of all animal families became extinct. The most significant losers included nearly all of the giant reptiles (leaving only the crocodile and turtle), the ammonites and the belemnites. Plants were relatively unscathed, and fishes were not significantly reduced in families. As a result, there was a completely different balance of living things on land at the beginning of the Cenozoic Era.
The Cenozoic Era The Tertiary Period
(Below) Tertiary ants in amber.
(Below) Tertiary gastropod.
Pliocene Epoch 1.6 million to 5 million years ago
Miocene Epoch 5 million to 26 million years ago
Oligocene Epoch 26 million to 37.5 million years ago
Eocene Epoch 37.5 million to 54 million years ago
Paleocene Epoch 54 million to 65 million years ago
Beginning of Ice Age
Largest sharks and whales Early humankind
First recorded occurrence of grasses First recorded large mammals Mammals become much more common
(Below) Quaternary mammoth tooth.
With the extinction of large reptiles many remaining families became more abundant. Molluscs and gastropods became numerous, but echinoids
and corals were much less common. Mammals developed quickly in this period. Starting as
small animals, they became rapidly bigger and more diverse, with legs and arms developed
for grasping or running, and specialised
teeth. Plant-eaters, such as horses, camels
and elephants, were soon followed by hunters such as cats. Hominids – people – developed at the end of the Tertiary Period.
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