Australasia

Australasia includes Australia and New Guinea. Australia's endemic mammals belong mainly to the order Marsupialia (the pouched mammals). Fewer large-mammal genera went extinct in Australia than in North America. However, one might argue that since it is smaller in area than North America, has a drier climate with poor soils (no vast rich loess deposits along a major interior drainage like the Mississippi), Australia deserves a handicap. In fact, if we define large mammals in Australia, which do not exceed 1,000 kilograms (2,200 pounds), as ranging down to 15 kilograms (about 30 pounds) in adult body weight, and compare them with those North American large mammals that range from 3,000 kilograms (6,600 pounds) down to 40 kilograms (roughly 90 pounds), and compare the extinction of species rather than genera, the records are comparable. Peter Murray (1991) lists 46 extinct species between 40 and 3,000 kilograms for North America north of Mexico and 41 extinct species between 15 and 1,000 kilograms for Australia (see figure 5). The number of taxa lost to extinction is similar; the mass of the species lost is greater in America.

Australasia saw the near-time extinction of Thylacoleo, the only genus of large mammalian carnivore that it had to lose. The best-known species of this genus, T. carnifex, is sometimes called the "marsupial lion."

Figure 3. The patterns of megafaunal extinctions in northern Eurasia. The timelines estimate the latest survival of selected large mammals in Europe and Siberia, including their relation to environmental changes and to replacement of Neanderthals by modern humans. The inferred extinction dates are staggered compared with the pulse of extinctions in North America at 11,000 C14 years ago. First to disappear are straight-tusked elephant and hippo; the last are the giant deer and woolly mammoth. The latter persisted on Wrangel Island until after 4000 C14 years ago. It is clear that extinctions do not cor-rolate with episodes of climatic change. They suggest that extinctions of temperate species (elephant and hippo) preceded those better adapted to high latitudes and colder climates as modern humans became better adapted to higher latitudes. Reprinted from MacPhee, ed., 1999. Used with kind permission of Springer Science and Business Media.

Figure 3. The patterns of megafaunal extinctions in northern Eurasia. The timelines estimate the latest survival of selected large mammals in Europe and Siberia, including their relation to environmental changes and to replacement of Neanderthals by modern humans. The inferred extinction dates are staggered compared with the pulse of extinctions in North America at 11,000 C14 years ago. First to disappear are straight-tusked elephant and hippo; the last are the giant deer and woolly mammoth. The latter persisted on Wrangel Island until after 4000 C14 years ago. It is clear that extinctions do not cor-rolate with episodes of climatic change. They suggest that extinctions of temperate species (elephant and hippo) preceded those better adapted to high latitudes and colder climates as modern humans became better adapted to higher latitudes. Reprinted from MacPhee, ed., 1999. Used with kind permission of Springer Science and Business Media.

Size Procoptodon With Human
Figure 4. Extinct Australian megafauna, scaled. A. Megalania (giant varanid lizard); B. Simosthenurus; C. Phascolonus; D. Zygomaturus; E. Procoptodon; F. Genyornis; G. Diprotodon; H. Macropus titan; I. Thylacoleo. From Murray 1991, in P.V. Rich et al., Vertebrate paleontology of Australasia.

It weighed up to 130 kilograms (about 285 pounds), intermediate in size between an African lion and a leopard. Although too old to date by radiocarbon, a remarkable number of well-preserved Thylacoleo carcasses have been discovered in sinkholes in the Nularbor Plain, a vast region of flat-lying karst limestone in south-central Australia. The carnivorous nature of Thylacoleo is suggested by its prominent incisors and large, bladelike premolars. It also had a large, hooked claw on each thumb, and, like us, it could move its thumbs independently of its other fingers, a useful feature if it was arboreal, as some paleontologists suspect was the case.

In Australia the predator-scavenger niche may have been partly filled by reptiles, as it is today. Megalania, a giant varanid or monitor lizard 5 to 9 meters (16 to 30 feet) in length, may have attained 880 kilograms, or 2,000 pounds (Molnar 2004). This is almost ten times the weight of its close relative the "ora" or Komodo dragon, the leopard, and the extinct Thylacoleo, according to recent estimates by Stephen Wroe (Wroe and others 2003). In weight, Megalania may have matched America's short-faced bear, Arctodus, as a giant carnivore. However, its reptilian physiology would have tolerated longer periods of starvation. Some sus-

North America

Australia

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