Cainozoic Era
About 65 million years ago to present.
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The Quaternary
About 1.78 million years ago to present.
This period is further divided into Pleistocene Epoch (duration about 1.77 million years) and Holocene Epoch (about 10 thousand years).
This was a period of successive ice ages, the last at its peak about 18000 years ago. Modern humans were present from about 100000 years ago. Some of the large mammals of the Northern Hemisphere and the giant megafauna of Australia became extinct about 50000 years ago.
Pictures of Quaternary life.
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The Tertiary (Sub-era)
About 65 to 1.78 million years ago.
This sub-era is further divided into Epochs named Paleocene (duration about 10.2 million years), Eocene (about 21.1 million years), Oligocene (about 9.8 million years), Miocene (about 18.5 million years) and Pliocene (about 3.5 million years).
This interval is sometimes called the 'Age of Mammals' because of the marked increase in the diversity and abundance of mammals of all kinds. Flowering plants, grasslands and deciduous trees were widespread, and insects, crocodiles, turtles, and tortoises continued to evolve. Fish increased in variety (including giant sharks more than 20 metres long about 15 million years ago). Most invertebrates were similar to those living today. Towards the end of the Tertiary, a number of very large mammals appeared. In the Northern hemisphere, these included ancestors of the mammoth and sabre-toothed cat; in Australia they were giant marsupials and lizards, and large, flightless birds.
Pictures of Tertiary life.
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Mesozoic Era
About 251 to 65 million years ago.
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Cretaceous Period
About 141 to 65 million years ago.
Dinosaurs dominated life on land; giant turtles and other marine reptiles, sponges and molluscs were abundant in the ocean. Birds developed into flying and flightless types. Marsupial and placental mammals, nectar-bearing plants and modern insects appeared. A mild climate favoured the growth of deciduous trees. Ichthyosaurs became extinct about 95 million years ago; dinosaurs, pterosaurs, plesiosaurs, ammonites, and many other animals became extinct 65 million years ago. The "Age of Reptiles" came to an end.
Pictures of Cretaceous life.
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Stegosaurus.
Photographer: Frank Coffa.
Source: Museum Victoria.
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Jurassic Period
About 205 to 141 million years ago.
Dinosaurs, flying pterosaurs and crocodiles were abundant, the first birds appeared, and a variety of small mammals evolved. Cycads and conifers were dominant. Ammonites, brachiopods and bivalves were in great abundance in the sea; aquatic reptiles such as ichthyosaurs were dominant in the oceans. Modern sharks appeared; frogs and toads replaced the large amphibians of past periods. The 'Age of Dinosaurs' continued.
Pictures of Jurassic life.
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Triassic Period
About 251 to 205 million years ago.
Mammal-like reptiles were dominant at the beginning of the Triassic, but were replaced by dinosaurs and the first mammals by the end of the period. This and the next two periods were the 'Age of Dinosaurs'. The first giant marine reptiles appeared; ammonoids, marine snails and bivalve molluscs were common. The first turtles and frogs appeared; cycads and conifers were dominant land plants.
Pictures of Triassic life.
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Palaeozoic Era
About 545 to 251 million years ago.
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Permian Period
About 298 to 251 million years ago.
This was a time of severe climatic variation and plant and animal extinctions. Deciduous trees and conifers became abundant, mammal-like reptiles and modern insects such as cicadas and beetles emerged; ammonites, brachiopods, bryozoans and corals flourished in the seas. The period ended with the greatest of all 'mass extinctions', with many plants and animals becoming extinct or much less diverse.
Pictures of Permian life.
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Carboniferous Period
About 354 to 298 million years ago.
Forests of tall evergreen trees, fern-like plants, horsetails and creepers lived in the swamps of this period, and eventually formed much of the Earth's coal. The period is therefore known as the 'Coal Age'. It is also known as the 'Age of Amphibians', as these were the dominant land animals. Corals and brachiopods were abundant in the sea. Reptiles and winged insects appeared on land.
Pictures of Carboniferous life.
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Devonian Period
About 410 to 354 million years ago.
Sponges, corals and brachiopods were abundant. The Devonian Period is often called the 'Age of Fishes' because of the evolution and spread of sharks and bony fish. The Devonian is also distinctive for the first appearance of insects and spiders. Amphibians appeared late in the period, as did ferns, horsetails and seed-ferns.
Pictures of Devonian life.
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Silurian Period
About 434 to 410 million years ago.
The first fossil evidence of land plants and animals (e.g. scorpions) is from this period. Brachiopods and graptolites were abundant. Eurypterids were fresh-water 'scorpions' that evolved to become the largest arthropods of all time (more than 2 metres long).
Pictures of Silurian life.
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Ordovician Period
About 490 to 434 million years ago.
Life was confined to the sea. The period is sometimes called the 'Age of Graptolites', but cephalopods, trilobites, corals and brachiopods were also numerous. Seaweeds were the only plants. The first well-preserved jawless fish are from the Ordovician.
Pictures of Ordovician life.
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Cambrian Period
About 545 to 490 million years ago.
The first fossils of animals with shells or hard parts occur in rocks of Cambrian age. Life in the Cambrian was confined to the sea and included the first representatives of many invertebrate animals. The first vertebrate animals are known from late in this period. The Cambrian is sometimes called the 'Age of Trilobites', as these were one of the most dominant life forms.
Pictures of Cambrian life.
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The Precambrian
About 4600 to 545 million years ago.
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The first evidence of life on Earth is from about 3500 million years ago. During the Precambrian, life was confined to the sea and consisted of simple, single-celled organisms such as bacteria, algae, and soft-bodied animals like jellyfish and worms.
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