Australian megafauna is a word used to describe a number of animal species in Australia that are quite a bit bigger than their closest living relatives. These species became extinct during the Pleistocene (16,100±100 - 50,000 years before present), but exact dates for their extinction have only been discovered recently.

Some mythological creatures from the Aboriginal dreamtime look a bit like animals from the prehistoric Australian megafauna.

Extinction
Scientists have been unable to agree on the reasons the megafauna became extinct. It is possible when humans came to Australia (around 48,000-60,000 years ago), and began hunting and using fire, they may have caused the extinction of the megafauna. Climate change, which made the country much drier during an Ice Age about 18,000 years ago, may have also have led to the extinction of the megafauna. Some scientists say that climate change alone caused the extinction of the megafauna. This argument does not allow for the fact that the megafaunal species had lived through two million years of climate changes. They had lived through a number of dry times before their sudden extinction.

New evidence
Scientists have got new evidence, based on new and better ways of finding dates, using optically stimulated luminescence and Uranium-thorium dating of megafaunal bones. This suggests that humans were the main cause of the extinction of megafauna in Australia. The dates show that the last of the megafauna became extinct around the same time, about 47,000 years ago. This was the time in which humans first arrived in Australia. The dates suggest the main reason for extinction was human burning of the land. Many plants were not able to survive regular fires, and so the types of plants changed. Scientists have studied oxygen and carbon isotopes from teeth of megafauna. These show sudden, dramatic, non-climate-related changes in plants, and in the diet of surviving marsupial animals, as well as the loss of megafaunal species. Further study of the teeth of megafauna shows the climate was dry at the time of extinction, similar to the dry climate of today, and that the megafauna were able to live in dry climates.

Living Australian megafauna

Extinct Australian megafauna: pre-1788 
The following is a list of some of the Australian megafauna. It shows:

 Latin name (scentific name), (common name, when it lived), and a brief description.

Mammals 
Mammals are set out by size with largest at the top.

1000-2000 kilograms 
 Diprotodon optatum  was the largest type of Diprotodontid. About three metres long, two metres high at the shoulder and weighing up to two tonnes, it looked like a giant wombat. It is the largest marsupial currently known.
Diprotodon minor
 Zygomaturus trilobus was a smaller, about the size of a cow, about two metres long and one metre high. It was a Diprotodontid that may have had a short trunk (like an elephant). It appears to have lived in wetlands, using two fork-like teeth to dig up reeds for food.
 Palorchestes azael (the Marsupial Tapir) was a Diprotodontoid, about the same size as the Zygomaturus, with long claws and a long trunk. It lived in the Pleistocene (Mackness 2009).

100-1000 kilograms
 Euowenia grata
 Nototherium mitchelli
 Euryzygoma dunense
 Phascolonus gigas
 Ramsayia magna
 Procoptodon goliah (the Giant Short-faced Kangaroo) is the largest kangaroo to have ever lived. It grew 2–3 metres (7–10 feet) tall, and weighed up to 230 kilograms. It had a flat, shortened face with jaw and teeth able to chew tough, desert plants. It had forward-looking eyes providing three dimensional vision. Procoptodon was one of seventeen species, in three genera in the Sthenurine subfamily, which are all extinct. Sthenurines lived in open woodlands in central northern Australia. All sthenurines had a hoof-like, fourth toe on the back legs. Their other toes were not fully formed. They also had elastic ligaments between the toe bones; this gave them more spring and speed compared to modern kangaroos. Sthenurine front legs were long, with two long fingers and claws, compared with the small, stiff arms of modern kangaroos. These may have been used for pulling branches nearer for eating and for walking on all four legs for short distances.
 Procoptodon rapha, P. pusio and P. texasensis
 Protemnodon a type of giant wallaby with four species.
 Palorchestes parvus
 Macropus pearsoni and M. ferragus

10-100 kilograms

 Simosthenurus pales
Sthenurus tindalei and S. atlas
 Phascolarctos stirtoni was a koala, the same as a modern koala, but one third larger.
 Phascolomys medius
 Lasiorhinus angustioens
 Congruus congruus a wallaby from Naracoorte.
 Troposodon minor
 Sthenurus oreas
 Simosthenurus occidentalis (another Sthenurine), about as tall as a modern Eastern Grey Kangaroo, but much stronger. It is one of the nine types of leaf-eating kangaroos found as fossils in the Naracoorte Caves National Park.
 Simothenurus brownei
 Propleopus oscillans (the Carnivorous Kangaroo), from the Miocene and Pliocene, was large rat kangaroo, up to , with large cutting and tough grinding teeth. These show it was a carnivore able to eat insects, animals (possibly carrion), fruits, and soft leaves. It grew to about  to   tall.
 Simothenurus maddocki
 Sthenurus andersoni
 Thylacoleo carnifex, (the Marsupial Lion), was the size of a leopard. It had a cat-like skull with large slicing teeth. It had a thumb-claw, that could be pulled back in, and very big front legs. It ate meat, and it lived in trees.
 Vombatus hacketti
 Macropus thor
 Macropus piltonensis
 Zaglossus hacketti was a sheep-sized echidna. It was found in Mammoth Cave in Western Australia, and is the largest monotreme so far discovered.
 Macropus rama
 Simothenurus gilli
 Warrendja wakefieldi a wombat from Naracoorte.
 Zaglossis ramsayi
 Sarcophilus harrisii laniarius was a large type of the Tasmanian Devil.
 Megalibgwilia ramsayi was a large, long-beaked echidna with powerful front legs for digging. It would have eaten worms and grubs, rather than ants.

Birds 

 Family Dromornithidae: this group of birds was closely related to waterfowl (ducks), not the modern ratites (emus and cassowaries).
 Dromornis stirtoni, (Stirton's Thunder Bird, Miocene epoch) was a bird that did not fly. It was  tall and weighed about . It is one of the largest birds so far discovered. It lived in subtropical open woodlands and may have been carnivorous. It was heavier than the Moa and taller than the Aepyornis.
 Bullockornis planei (the 'Demon Duck of Doom') was another large member of the Dromornithidae. It was up to  tall and weighed up to , and was probably carnivorous.
 Genyornis newtoni (the Mihirung) was related to Dromornis. It was about the height of an ostrich. It was the last survivor of the Dromornithidae. It had a large lower jaw and was probably omnivorous.
 Leipoa gallinacea (formerly Progura) was a giant malleefowl.

Reptiles 

 Varanus priscus (formerly Megalania prisca) was a giant, carnivorous goanna that might have grown to as long as , and weighed up to  (Molnar, 2004).
 Wonambi naracoortensis was a snake about  in length. It would catch animals at a water hole and kill by crushing. It was not a poisonous snake.
 Quinkana sp., was a land crocodile, which grew up to  in length. It had long legs positioned underneath its body, and chased down mammals, birds and other reptiles for food. Its teeth were sharp for cutting, not pointed for gripping like water living crocodiles. It was part of the Mekosuchine subfamily (all now extinct). It was discovered at Bluff Downs in Queensland.
 Liasis sp., (Bluff Downs Giant Python), lived during the Pliocene epoch, grew up to  long, and is the largest Australian snake known. It hunted mammals, birds and reptiles in woodlands near rivers. It is similar to the Olive Python (Liasis olivacea).
Meiolania was a group of huge land cryptodire turtle measuring  in length, with a horned head and spiked tail.

References 

 Field, J. H. and J. Dodson. 1999. Late Pleistocene megafauna and archaeology from Cuddie Springs, south-eastern Australia. Proceedings of the Prehistoric Society 65: 1-27.
 Wroe, S., J. Field, and R. Fullagar. 2002. Lost giants. Nature Australia 27(5): 54-61.
 Mackness, B.S. 2009. Reconstructing Palorchestes (Marsupialia: Palorchestidae) — from Giant Kangaroo to Marsupial ‘Tapir’. Proceedings of the Linnean Society of New South Wales 130: 21-36.
Gavin J Prideaux, Richard G. Roberts, Dirk Megirian, Kira E. Westaway, John C. Hellstrom, John M. Olley. 2007. Mammalian responses to Pleistocene climate change in southeastern Australia. Geology, v. 35, n. 1, p. 33-36.

Other websites 
 Cuddie Springs 
 Interview with Dr John Long, curator at the Museum of Victoria
 Naracoorte caves in South Australia 
 Lost Kingdoms 

Lists of animals
Animals of Australia