Australia: The Land Where Time Began
Significant Events in Australia's Biological History
| Cainozoic | 10,000 ya | Holocene | Also called recent. In Australia biotas are much the same as present. |
| 2 Ma | Pleistocene | Aboriginal People arrived between 50,000 and 120,000 BP, probably about 60,000 BP. Extinction of many megafauna species. Those represented at Naracoorte around 35,000 BP - perhaps because of climate change and human activity. Dingoes introduced about 4,000 BP. Cool dry climate and low sea levels alternate with warm wet climate and high sea levels as polar ice caps expand and contracted. | |
| 5.2 Ma | Pliocene | Australia drifts into lower latitudes, cools and aridity sets in. Rainforests continue to decline and eucalypts and grasslands continue to spread. First appearance of a variety of modern types of animals including specialised grazers. Many lineages become gigantic - megafauna. | |
| 23.3 Ma | Miocene | Early to Mid Miocene characterised by lush forests (e.g., at Riversleigh). Australia crashed into islands of south-eastern Asia, and soon after rodents enter Australia. By Late Miocene rainforests decline and grasslands begin to spread. | |
| 35.4 Ma | Oligocene | By the end of this period koala, kangaroos, possums and other modern families present. Fossil deposits in Tasmania, South Australia and Queensland contain diverse vertebrates faunas, most indicative of forest communities. | |
| 56.5 Ma | Eocene | Rainforest covers much of southern Australia. Australia's oldest marsupials, bats, frogs, and snakes. (Murgon). Non-marine mammals known from Antarctica-where forests still flourish. | |
| Cainozoic | 65 Ma | Palaeocene | World climates cool. Mammals begin to diversify on all continents following decline of dinosaurs. First horses, primates, carnivores and other groups appear. Marsupials diversify at least in South America. |
| Mesozoic | 145.6 Ma | Cretaceous | In the early part of this period, Australia is covered by shallow seas. There were many giant aquatic reptiles in the seas. Flowering plants appear and rapidly spread. Conifers and cycads decline. At the end of the period dinosaurs and other groups became extinct. Australia's oldest known mammal is a platypus-like animal. Australia's oldest birds. At least some exchange of plants took place between Australia and the lands to the north. |
| 210 Ma | Jurassic | Australia's climate is warm and wet. Conifers, ferns and cycads are plentiful. Many large herbivorous and aquatic reptiles. Ray-finned fishes present. Earliest birds found in Northern Hemisphere. See also Mammals diversify, but are tiny, not bigger than mice. | |
| Mesozoic | 245 Ma | Triassic | Mammal-like reptiles present on all continents. Australia's climate gets warmer and drier. Insects, primitive amphibians and reptiles well represented. Gondwana begins to break up. First mammals known from many continents, but not Australia. Many groups went extinct or sharply declined at the end of this period. |
| Palaeozoic | 290 Ma | Permian | Glaciers cover parts of Gondwana. Climates changes to more temperate with swamp forests. Insects, fish and early amphibians plentiful, but in Australia, no reptiles. Trilobites go extinct, major mass extinction at the end of this period. |
| 362.5 Ma | Carboniferous | Starts with warm conditions, then glaciers over much of Gondwana rifts from Laurasia and drifts towards the South Pole. Club mosses die out and are replaced by hardier seed ferns. Many kinds of fish and amphibians. First reptiles appear in the Northern Hemisphere. | |
| 408.5 Ma | Devonian | Plants spread from water margins into swampy areas forming thick vegetation with tree-like club mosses and ferns. Fish have diversified, lungfish, sharks and armoured fish in sea and fresh water. First amphibians evolve and move onto the land. | |
| 439 Ma | Silurian | Life invades the land. Land plants evolve from seaweeds. Jawless fish and sea "scorpions" live in fresh water. First fish with jaws appear in seas. First coral reefs formed. | |
| 510 Ma | Ordovician | Varieties of marine life become extensive, brachiopods, bivalves, crinoids, first jawless fish evolve. Australia's being among the earliest. | |
| Palaeozoic | 570 Ma | Cambrian | No life on land, but seas teaming with life, including jellyfish, sea anemones, sponges, trilobites, brachiopods and molluscs. |
| Proterozoic | 2 Ga |
Precambrian
|
Oxygen becomes abundant in atmosphere and life diversifies. Multicellular organisms develop from single cellular organisms. Algae, jellyfish, primitive worms and sponges appear. |
| Archaean | 4.5 Ga |
Precambrian
|
Life evolves at least by 3.5 Ga. Some cyanobacteria produce oxygen that forms ozone that shields the Earth from UV radiation that allows life to exist. |
| Author: M. H. Monroe |
| Email: admin@austhrutime.com |
| Last Updated 25/02/2011 |
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