---
title: "Natural history of Australia"
chunk: 2/2
source: "https://en.wikipedia.org/wiki/Natural_history_of_Australia"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:46:52.520128+00:00"
instance: "kb-cron"
---

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 Mesozoic, when the Earth became much warmer, 251 to 140 Ma, the  Australian landmass was covered with riverine plains. Humid conditions allowed the formation of peatlands, particularly in the east. Dinosaurs, reptiles and primitive mammals were present in Australia. Between 140 and 99 Ma, sea levels rose, and much of the continent was covered. In the same period (between 120 and 105 Ma), there was more volcanism in eastern Australia, leading to uplift creating the Tasman Sea to the southeast and the Coral Sea to the north.
The earliest land plants preserved in Australia occur in deposits from the Upper Silurian and the Lower Devonian in marine sediments in Victoria, named the Baragwanathia Assemblage for its most prominent element, the simple vascular plant the lycopod Baragwanathia. The assemblage also included Rhyniophyta, Zosterophyllophyta, and Trimerophyta in addition to other lycopods. All these plants were herbaceous, coastal and required an aqueous environment for reproduction. During the Devonian the first shrub-sized to tree-sized lycopods appeared in Australia and Antarctica; they dominated the flora until the Early Carboniferous. In the mid- to Late Carboniferous, as Australia drifted from equatorial latitudes to polar latitudes, the lycopods waned and were replaced by seed-ferns, and the Nothorhacopteris-Fedekurtzia-Botrychiopis complex.
Most of the modern Australian fauna had its origin in the Cretaceous. From pollen records from the Late Cretaceous it is proposed that the flora of the Cretaceous either evolved within the Austro-Antarctic region or entered Australia from Antarctica. Angiosperms evolved in the northern Gondwana/southern Laurasia during the Early Cretaceous and radiated worldwide. Prominent members of this early angiosperm flora were the Nothofagus.
Fossils found at Lightning Ridge, New South Wales, suggest that 110 million years ago Australia supported a number of different monotremes, but did not support any marsupials. Marsupials appear to have evolved during the Cretaceous in the contemporary northern hemisphere, to judge from a 100-million-year-old marsupial fossil, Kokopellia, found in the badlands of Utah. Marsupials would then have spread to South America and Gondwana. 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. The Murgon fossil site has yielded a range of marsupial fossils, many with strong South American connections — unsurprising since the two continents were both a part of Gondwana. At Murgon evidence of a placental mammal, a Condylarth (Tingamarra porterorum), was discovered. Placental 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.
Regarding Australian Flora, the first evidence of life created by photosynthesis dates back to 3500 million years ago. The evidence of photosynthesis comes from sedimentary structures called stromatolites, which are built from photosynthesis. These are unambiguous records of life, as they still exist today. 

== Isolation ==

The Devonian period (419–359 Ma) saw 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 on the continent 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 Nanantius, a small primitive flying bird known from one leg bone 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 eastern and southeastern Australia, and consist of isolated jaws and postcranial bones from Lightning Ridge, New South Wales and sites near Inverloch, Victoria, dated at between 120 and 110 Ma. These mammals lived at a time when Australia comprised part of the supercontinent Gondwana, which at that time also included Antarctica and New Zealand.
Australia separated from Antarctica in the Late Eocene (c45-30 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 Miocene (23 to 5.3 Ma) and into the Pleistocene (20,000–50,000 years before present) the Australian megafauna developed. 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. The World Heritage-listed Naracoorte Caves in South Australia are the best record of the Australian megafauna. The placental mammals made their reappearance in Australia in the Pleistocene, as Australia continued to move closer to Indonesia, both bats and rodents appearing reliably in the fossil record. The geographic isolation of Australia created a sharp division between Australian fauna and Asian fauna at the Wallace Line.

== See also ==
Geology of Australia
List of Australian and Antarctic dinosaurs
Natural history of New Zealand
South Polar dinosaurs

== Notes and references ==

=== Notes ===

=== References ===

== External links ==
Fossil Sites of Australia