and water courses. It would have coexisted with many of the so-called Australian megafauna such as Diprotodon, giant kangaroos, and Megalania, as well as giant wallabies like Protemnodon, the giant wombat Phascolonus, the giant snake Wonambi, and the thunderbird Genyornis. T. hilli was a similar size to a contemporaneous thylacinid species, Wakaleo alcootaensis, and may have occupied habitat to the exclusion of that carnivore. Australia's Pleistocene megafauna would have been the prey for the agile T. carnifex, who was especially adapted for hunting large animals, but was not particularly suited to catching smaller prey. The relatively quick reduction in the numbers of its primary food source around 40,000 to 50,000 years ago probably led to the decline and eventual extinction of the marsupial lion. The arrival of humans in Australia and the use of fire-stick farming precipitated their decline. The extinction of T. carnifex makes Australia unique from the other continents because no substantial, apex mammalian predators have replaced the marsupial lions after their disappearance. Extinction It was believed that the extinction was due to the climate changes, but human activities as an extinction driver of the most recent species is possible yet unproven. There is a growing consensus that the extinction of the megafauna was caused by progressive drying starting about 700,000 years ago (700 ka). It is revealed recently that there was a major change in glacial-interglacial cycles after ~450 ka. As for human involvement's contribution to the extinction, one argument is that the arrival of humans was coincident with the disappearance of all the extinct megafauna. This is supported by the claims that during MIS3, climatic conditions are relatively stable and no major climate change would cause the mass extinction of megafauna including Thylacoleo. Although believed to have been a victim of climate change, some scientists now believe Thylacoleo to have been exterminated by humans altering the ecosystem with fire in addition to hunting its prey. "They found Sporormiella spores, which grow in herbivore dung, virtually disappeared around 41,000 years ago, a time when no known climate transformation was taking place. At the same time, the incidence of fire increased, as shown by a steep rise in charcoal fragments. It appears that humans, who arrived in Australia around this time, hunted the megafauna to extinction". Following the extinction of T. carnifex, no other apex mammalian predators have taken its place. Discoveries The first specimens of Thylacoleo were