The Cenozoic Era in Australia

The Cenozoic Era was the era of mammals.

Cenozoic era starts with the extiniction of dinosaurs 65 million years ago.

Although the first mammals evolved not long after dinosaurs in the end of Triassic period, mammals were small and unable to compete with the successful dinosaurs during the Mesozoic Era.
A Brontotherium Leaves His Forest Habitat in Search of a Meal
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Now that the dinosaurs were extinct, mammals got the chance and started evolving into many different species including large animals. The Eocene Epoch saw the first whales and primates. Then there were some cold times with ice ages during Oligocene, Miocene and Pliocene. Homo Erectus and Homo Habilis evolved in the late Pliocene, while Neanderthals and Homo sapiens evolved in the end of Pleistocene.

An Elasmotherium Grazing
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Australia during the Cenozoic Era
For Australia, the extinction of dinosaurs roughly coincided with the final breakup of Gondwanaland, when Australia and Antarctica separated from each other and Australia finally got the shape it has today.

A Paraceratherium Mother Grazes on Leaves and Twigs of a Poplar Tree
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Australia is a Moist Continent
Antarctica was not covered in ice, and Australia was a much moister continent than it is today. It was covered in tropical rainforests, remaining pockets of which can still be seen in Daintree in north Queensland, Finke Gorge in Northern Territory, and Carnarvon Gorge in central Queensland, amongst others.

Brontotherium Wander the Lush Late Eocene Landscape
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Australian Continent Dries
But about 30 million years ago, Australia had drifted far enough away from Antarctica that a complete circumpolar current could form around Antarctica. First that current was reasonably warm, and both continents still supported temperate rainforests. About 15 million years ago however, the temperatures got cooler and Antarctica developed glacial conditions. As the ice cover growed on Antarctica, Australia got drier, partly because of the amount of water that is tied up in glaciers. The drying of Australia has been going on, with small exceptions, until today, when 2/3 of Australian continent is covered in deserts and semi-deserts.

A Pack of Dire Wolves Crosses Paths with Two Mammoths During the Upper Pleistocene Epoch
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The Oldest Mammal Fossils in Australia
Some of the oldest animal fossils found in Australia are these of platypus - the monotreme mammal that has apparently been living here continuously for 110 million years (way back into the age of dinosaurs!). The oldest bird fossil is a 115 million years old feather, and the oldest frog fossil dates back to 54.5 million years.

A Megalodon Shark from the Cenozoic Era
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Megafauna of the Cenozoic Era
As in many other parts of the world, some species of Australian mammals developed into very large animals. Such "megafauna" evolved in Australia about 1 million years ago, and included giant kangaroos, echidnas, wombats, 3m-high emus, 7m-long goannas and some species with no living relatives such as diprotodons, palochesters, and carnivorous marsupial lions that could climb trees. All these megafauna got quite suddenly extinct in Australia about 46,000 years ago. A hotspot for megafauna fossils is the Riversleigh fossil field in Lawn Hill National Park in north-western Queensland.

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