Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are primarily found in Australasia, Wallacea, and the Americas. One of the defining features of marsupials is their unique reproductive strategy, where the young are born in a relatively undeveloped state and then nurtured within a pouch.
The platypus, sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. The platypus is the sole living representative or monotypic taxon of its family Ornithorhynchidae and genus Ornithorhynchus, though a number of related species appear in the fossil record.
The fauna of Australia consists of a large variety of animals; some 46% of birds, 69% of mammals, 94% of amphibians, and 93% of reptiles that inhabit the continent are endemic to it. This high level of endemism can be attributed to the continent's long geographic isolation, tectonic stability, and the effects of a unique pattern of climate change on the soil and flora over geological time. A unique feature of Australia's fauna is the relative scarcity of native placental mammals. Consequently, the marsupials – a group of mammals that raise their young in a pouch, including the macropods, possums and dasyuromorphs – occupy many of the ecological niches placental animals occupy elsewhere in the world. Australia is home to two of the five known extant species of monotremes and has numerous venomous species, which include the platypus, spiders, scorpions, octopus, jellyfish, molluscs, stonefish, and stingrays. Uniquely, Australia has more venomous than non-venomous species of snakes.
The Wallace line or Wallace's line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace and named by the English biologist T.H. Huxley that separates the biogeographical realms of Asia and 'Wallacea', a transitional zone between Asia and Australia also called the Malay Archipelago and the Indo-Australian Archipelago. To the west of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origins is present. Wallace noticed this clear division in both land mammals and birds during his travels through the East Indies in the 19th century.
The tiger quoll, also known as the spotted-tail quoll, the spotted quoll, the spotted-tail dasyure, native cat or the tiger cat, is a carnivorous marsupial of the quoll genus Dasyurus native to Australia. With males and females weighing around 3.5 and 1.8 kg, respectively, it is the world's second-largest extant carnivorous marsupial, behind the Tasmanian devil. Two subspecies are recognised; the nominate is found in wet forests of southeastern Australia and Tasmania, and a northern subspecies, D. m. gracilis, is found in a small area of northern Queensland and is endangered.
The northern quoll, also known as the northern native cat, the North Australian native cat or the satanellus is a carnivorous marsupial native to Australia.
The dibbler is an endangered species of marsupial. It is an inhabitant of the southwest mainland of Western Australia and some offshore islands. It is a member of the order Dasyuromorphia, and the only member of the genus Parantechinus. The dibbler is a small, nocturnal carnivore with speckled fur that is white around the eyes.
The long-nosed potoroo is a small, hopping mammal native to forests and shrubland of southeastern Australia and Tasmania. A member of the potoroo and bettong family (Potoroidae), it lives alone and digs at night for fungi, roots, or small insects. It is also a marsupial and carries its young in a pouch. The long-nosed potoroo is threatened by habitat loss and introduced species such as cats or foxes. There are two subspecies: P. t. tridactylus on mainland Australia, and P. t. apicalis on Tasmania, with lighter fur.
The kultarr is a small insectivorous nocturnal marsupial inhabiting the arid interior of Australia. Preferred habitat includes stony deserts, shrubland, woodland, grassland and open plains. The kultarr has a range of adaptations to help cope with Australia's harsh arid environment including torpor similar to hibernation that helps conserve energy. The species has declined across its former range since European settlement due to changes in land management practices and introduced predators.
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 mammalian predators in Australia, the Tasmanian tiger and the marsupial lion, bore a striking resemblance to large canids such as the gray wolf and large cats respectively; 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 or omnivores.
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.
The fauna of New Guinea comprises a large number of species of mammals, reptiles, birds, fish, invertebrates and amphibians.
The narrow-nosed planigale is a species of very small marsupial carnivore of the family Dasyuridae.
The crest-tailed mulgara is a small to medium-sized Australian carnivorous marsupial and a member of the family Dasyuridae which includes quolls, dunnarts, the numbat, Tasmanian devil and extinct thylacine. The crest-tailed mulgara is among a group of native predatory mammals or mesopredators endemic to arid Australia.
Monotremes are mammals of the order Monotremata. They are the only known group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. Although they are different from almost all mammals in that they lay eggs, like all mammals, the female monotremes nurse their young with milk.
A unique and diverse albeit phylogenetically restricted mammal fauna is known from the Caribbean region. The region—specifically, all islands in the Caribbean Sea and the Bahamas, Turks and Caicos Islands, and Barbados, which are not in the Caribbean Sea but biogeographically belong to the same Caribbean bioregion—has been home to several families found nowhere else, but much of this diversity is now extinct.
