Natural history of Australia

The building of the Australian continent and its association with other land masses, as well as climate changes over geological time, have created the unique flora and fauna present in Australia today.

During the Proterozoic, 2,500 to 545 Ma, continent building took place around the existing cratons; the accretions include sedimentary deposition of the banded iron formations and the formation of Australia's major orebodies – sources of gold, copper, lead, zinc, silver and uranium.

From 545 to 390 Ma shallow warm seas covered parts of central Australia, with a series of volcanic arcs and deep water sedimentation in the east.

During the Devonian the first shrub-sized to tree-sized lycopods appeared in Australia and Antarctica; they dominated the flora until the Early Carboniferous.

The first evidence of marsupials in Australia comes from the Tertiary, and was found at a 55-million-year-old fossil site at Murgon, near Kingaroy in southern Queensland.

It was not until the Devonian period (419–359 Ma) that we see the first great diversification of fishes living within Australian freshwater basins and in marginal marine embayments.

Australia has a rich fossil record of early amphibians which first appeared here around 370–375 Ma, based on well-preserved ‘tetrapod’ trackways at Genoa River, Victoria.

The oldest of these remains are of Triassic age and comprise a few superficially lizard-like taxa such as prolacertids (e.g. Kadimakara), and thecodonts.

Two of the world's three major groups of extant mammals had their origin in the Australian part of the Gondwana supercontinent, the monotremes and marsupials.

These lived at a time when Australia was part of a small Gondwana (also including Antarctica and New Zealand) which was beginning to drift apart.

They are based on isolated jaws and postcranial bones from Lightning Ridge, New South Wales and southern Victoria sites (near Inverloch), dated at between 120 and 110 Ma.

The megafauna became extinct in the late Pleistocene, at a time coinciding with both a period of climate change and the first human habitation of Australia.

Recent analysis suggests that the fire-stick farming methods of the Australian Aborigines reduced plant diversity and contributed to the extinction of large herbivores with a specialised diet, like the flightless birds from the genus Genyornis.