Collectively, these large extinct animals are known as the ‘megafauna’. They lived together with the same animals we see today, but disappeared sometime within the last 50,000 years.

Why did megafauna become extinct?
There are several theories as to why megafauna disappeared. Australia has experienced several ice ages over the last million years casing enormous changes to the landscape. This change in climate and the environment may have been unsuitable for many of the large leaf-eating herbivores causing them, and their predators, to die out.

The timing of the extinctions also appears to coincide with the arrival of Aborigines to mainland Australia. Aborigines may have hunted the large slow-moving animals and altered their habitats through frequent burning.

The combination of these factors may have been what was needed to push the megafauna to extinction, as they struggle to survive the changing Australian environment and the appearance of humans.

Included in the Wonambi display are the following 13 extinct species:

• Diprotodon australis • the largest marsupial to ever live in Australia, weighing over two tonnes. It is rarely found in the cave deposits, because its sheer size prevented it from falling through most cave openings.
  
• Simosthenurus occidentalis • stood no taller than a modern grey kangaroo, but was much more robust. It is one of the nine species of leaf-eating kangaroos identified at Naracoorte.
  
• Progura naracoortensis • a giant malleefowl was also first described from Naracoorte’s fossils.
  
• Procoptodon goliah • the largest of the leaf-eating kangaroos (200kg) could stand on tiptoe, prop on its tail and reach leaves up to three metres from the ground. The skull is short and deep, an indication it had enough power in its jaws to grind up very tough leaves.
  
• Megalania prisca • a goanna of terrifying proportions, 6 metres long and able to look you in the eye. The first fossil of this goanna was only found at Naracoorte in 2000.
  
• Megalibgwilia ramsayi • a very large, long-beaked echidna with powerful digging forelimbs. Their diet would probably have included worms and grubs rather than ants.
  
• Palorchestes azael • originally described as a giant kangaroo based on a few fossil teeth. As more fossils of this species were found, researchers realised that it must have walked on four legs. Palorchestes may also have had a small trunk, hence the name “marsupial tapir”.
  
• Thylacoleo carnifex • commonly called the marsupial lion, it had a cat-like skull with large slicing premolars or cheek teeth. Combined with a large retractable thumb claw and powerful forelimbs this animal would have been a fearsome predator.
  
• Phascolarctos stirtoni • a koala similar to the existing species, but about one third larger.
  
• Sarcophilus laniarius • a large form of the modern Tasmanian Devil.
  
• Thylacinus cynocephalus • the thylacine or Tasmanian tiger is now extinct, the last one dying in the Hobart Zoo in 1936. Despite numerous reports each year, there has been no proof presented to show the animal is still alive.
  
• Wonambi naracoortensis • a large, non-venomous snake grew to a length of five to six metres and killed its prey by constriction. Wonambi is an Aboriginal word for the rainbow serpent. The species name naracoortensis reflects the fact it was first described from fossils found at Naracoorte.
  
• Zygomaturus trilobus • a marsupial with no modern day comparisons that probably lived in the wetter areas of Australia, feeding on clumps of reeds and sedges it shovelled up with two fork-like front incisors. The skull has raised nostrils that would be an advantage to the animal when feeding in water.
  

• Sthenurus andersoni
• Simosthenurus baileyi
• S. brownei
• S. gilli
• S. maddocki
• S. newtonae
• S. pales
• Protemnodon anak
• P. brehus

Many fossils of megafauna have been found, yet some animals are still only known from single or very few specimens, for example Propleopus oscillans (a giant rat kangaroo), Congruus congruus (a Wallaby) and Warendja wakefieldi (a wombat).