Natural history of Australia
The natural history of Australia has been shaped by the geological evolution of the Australian continent from Gondwana and the changes in global climate over geological time. 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.
Precambrian
Three areas of the Australian landmass that are made of
Rodinia broke up between 830 and 745 Ma; at around 750 Ma the western side of Rodinia called Laurentia broke away from the landmass made from Australia, India and Antarctica, forming a gap that would become the Pacific Ocean.
The Archean rocks from the Pilbara craton contain some of the first evidence of life, primitive cyanobacterial mats known as stromatolites. Soft-bodied organisms from the Ediacaran collectively known as the Ediacaran biota are found in sandstone around the Flinders Ranges in South Australia, notably at a site known as Wilpena Pound.
Gondwana
Following the breakup of Rodinia, Australia, India and Antarctica made up a large landmass. During plate movements from 750 to 500 Ma South America and Africa moved toward India and Australia, and by 500 Ma South America and Africa had joined with them to form Gondwana.
During the
The continents that had drifted away from Rodinia drifted together again during the
During the Carboniferous glaciation, erosion by ice extended into the Early Permian. Crustal extension and subsidence around 295 Ma formed shallow basins in which thick coal deposits were formed.
During the
The earliest land plants preserved in Australia occur in deposits from the Upper
Most of the modern Australian fauna had its origin in the
Fossils found at
mammals were also found in North America and South America at this time. This find suggests that placental mammals did coexist with marsupials in Australia in the early Tertiary, although only marsupials persisted.Isolation
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 fossil record of reptiles in Australia starts in the Mesozoic Era (250–66 Ma). 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. The earliest significant Australian bird fossil is that of a small primitive flying bird (an enantiornithine), known from one leg bone, Nanatius eos, found in 110 Ma marine sediments in Queensland. 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. The oldest mammal fossils from Australia are monotreme fossils from the Cretaceous of Southern Australia. 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. Several taxa (Teinolophos, Bishops) existed alongside primitive tribosphenic mammals like Ausktribosphenos.
Australia separated from Gondwana 99 Ma, and initially remained warm and humid with rainforest vegetation. Inland Australia had systems of rivers and lakes with abundant wildlife. Fossil birds, platypus, frogs and snakes are present from this period. From 30 Ma there was a period of global cooling, and from 15 Ma the Antarctic ice sheet formed. Sand deserts and large inland salt lakes formed within the last 5 Ma. Climatic oscillation during the Pleistocene over the last million years led to repeated phases of glaciation with lower sea levels that linked Australia to New Guinea, and warmer interglacial periods with higher sea levels.
As early as the
See also
- Geology of Australia
- List of Australian and Antarctic dinosaurs
- Natural history of New Zealand
- South Polar dinosaurs
Notes and references
Notes
References
- G. R. Dyne & D. W. Walton, ed. (1987). Fauna of Australia (Volume 1A – General Articles). Canberra: Australian Government Publishing Service. ISBN 0-644-06055-7.
- Johnson, David P. (2004). The Geology of Australia. ISBN 0-521-84121-6.
- Hill, R. S.; E. M. Truswell; S. McLoughlin; M. E. Dettman (1999). "The Evolution of the Australian Flora: Fossil Evidence Volume 1—Introduction". In A. E. Orchard and H. S. Thompson (ed.). Flora of Australia (2nd ed.). Australian Biological Resources Study/CSIRO Publishing. pp. 251–320. ISBN 0-643-05965-2.
External links
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