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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 Australia's mammals are herbivores and or carnivores. ==Evolutionary history== The fossil record shows that monotremes have been present in Australia since the Early Cretaceous 145–99 MYA.〔 Archer, M. et al., 1985. First Mesozoic mammal from Australia-an early Cretaceous monotreme. ''Nature'' 318:363–366〕 Marsupials probably existed in Australia at least from the early Paleocene (64-65 MYA), 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 (rats), several thousand years ago (dingo), and 200 years ago (many species); the last two were made by humans. Some claims were made about placental mammal fossils from the Eocene of Australia,〔 Godthelp, H. et al. 1992. Earliest known Australian Tertiary mammal fauna. ''Nature'', 356:514–516〕 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.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mammals of Australia」の詳細全文を読む スポンサード リンク
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