Cambrian Period

Cambrian Period covers the time between 545 and 490 million years ago.

It starts after a long period (longer than the whole Paleozoic Era which the Cambrian is only a part of) of ice ages and mass extinctions in the end of Precambrian Era.

 Artist's Concept of a Young, Turbulent Earth
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As the ice ages ended and the climate got warmer, a lot of warm shallow seas were created.

Artist's Concept Showing How the Surface of Earth Appeared During the Hadean Eon
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Conditions were perfect for the Cambrian Explosion - the event where, after almost 3000 years of primitive life consisting of procaryotic and eukaryotic cells and stromatolite-forming cyanobacteria, an amazing amount of animal species suddenly evolved only within a few million years - leaving behind a lot of Cambrian fossils.

Mountain Peak with a Sunlit Layer of Cambrian Limestone
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Cambrian animals were marine animals such as shellfish, corals, gastropods, crinoids, bivalves, graptolites, ammonites, brachipods, bryozoans and trilobites - still primitive compared to today's animals, but they were the first animals with skeletons (either shells or vertebrates); and trilobites were the first animals with eyes. Before the Cambrian period, no-one had actually seen the world.

A Species of Pirania, a Primitive Sponge That Populated the Ocean Floors 505 Million Years Ago
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Australia was still connected to Gondwana continent, and the eastern third of it, from Cape York peninsula in north to Adelaide in south, was deep, open ocean. .

Portuguese Man O' War Swarm over the Surface of a Cambrian Ocean
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Tasman Line - a line drawn inland from Cairns to south-western Queensland and north-eastern South Australia, then a turn to New South Wales (Broken Hill) and then south-west to Kangaroo Island - marks the original coastline of Gondwana, and the eastern edge of Precambrian Rocks.

A Moon Rises over a Young World
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Shallow seas covered much of Northern Territory and South Australia. Most of Cambrian fossils in Australia are found in sedimentary rocks in these areas. Some good examples are Flinders Ranges in South Australia, MacDonnells Ranges in Northern Territory and Kimberleys in northern Western Australia. There are no records of Cambrian rocks in southern WA.

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