This video says about itself:
Mammals of Australia – Video Learning – WizScience.com
16 aug. 2015
The “mammals of Australia” have a rich fossil history, as well as a variety of extant mammalian species, dominated by the marsupials, but also including monotremes and placentals. The marsupials evolved to fill specific ecological niches, and in many cases they are physically similar to the placental mammals in Eurasia and North America that occupy similar niches, a phenomenon known as convergent evolution. For example, the top predator in Australia, the Tasmanian tiger, bore a striking resemblance to canids such as the gray wolf; gliding possums and flying squirrels have similar adaptations enabling their arboreal lifestyle; and the numbat and anteaters are both digging insectivores. Most of Austarlia’s mammals are herbivores and or carnivores.
The fossil record shows that monotremes have been present in Australia since the Early Cretaceous 145–99 MYA.
Marsupials probably existed in Australia at least from the early Paleocene, although the earliest found undoubted fossils of Australian marsupials are from the late Oligocene 25 MYA.
The indisputable remains of Australian placental mammals started from the Miocene, when Australia moved closer to Indonesia. After 15 MYA bats appeared reliably in the fossil record, and after 5-10 MYA rodents did. The subsequent introductions of placental mammals into Australian fauna were about 1 MYA , several thousand years ago, and 200 years ago ; the last two were made by humans.
Some claims were made about placental mammal fossils from the Eocene of Australia, called “Tingamarra“. These claims are based on only one found tooth having some characteristic features of condylarth, and were discussed widely. But both the age and placental nature of these fossils were challenged by other researchers.
From the Mammal Review:
The good, the bad, and the ugly: which Australian terrestrial mammal species attract most research?
6 March 2016
1. The Australian mammalian fauna is marked by high endemism and evolutionary distinctiveness and comprises monotreme, marsupial, and eutherian (‘placental’) native species. It has suffered the highest extinction rate of any mammalian fauna in any global region; surviving species are threatened by competition and predation from a range of introduced mammal species, and receive low levels of conservation-oriented funding compared with species in many other countries.
2. We investigated research foci on this unique fauna by using species h-indices (SHI), and identified both taxonomic bias and subject bias in research effort and research impact for 331 Australian terrestrial mammal species. Species broadly fell into categories we labelled as the ‘good’, the ‘bad’, and the ‘ugly’.
3. The majority of studies on monotremes and marsupials (the ‘good’) are directed towards their physiology and anatomy, with a smaller ecological focus. By contrast, introduced eutherians (the ‘bad’) have attracted greater attention in terms of ecological research, with greater emphasis on methods and technique studies for population control. Despite making up 45% of the 331 species studied, native rodents and bats (the ‘ugly’) have attracted disproportionately little study.
4. While research on invasive species is directed towards problem solving, many Australian native species of conservation significance have attracted little research effort, little recognition, and little funding. Current global and national conservation funding largely overlooks non-charismatic species, and yet these species may arguably be most in need of scientific and management research effort.