AUSTRALIA'S GIANT ANIMALS:

The Megafauna

 information from The Australian Museum

 

Tourists and pleasure-seekers had visited the spectacular limestone formations in Naracoorte Caves for over a century, unaware that within nearby hidden chambers a detailed record of the local fauna had been steadily accumulating for more than 3,000 centuries. Cave explorer Grant Gartrell and palaeontologist Rod Wells of Flinders University were exploring Victoria Cave hoping to find fossil bones when they broke through to a concealed passageway. In the unexplored caverns beyond they discovered the largest, most diverse and best-preserved Pleistocene vertebrate fossil assemblage in Australia, in what is now known as the Fossil Chamber.

For more than 300,000 years sediment and animal bones filled the Fossil Chamber through an opening in the ceiling, forming an enormous cone-shaped pile. The cave acted like a huge natural pitfall trap: animals that fell in were unable to escape through the high entrance and died, their skeletons lying nearly undisturbed for millennia. As the cone grew, fans of sediment and animal bones spread out over the cave floor. The sediment pile eventually grew up to the ceiling and blocked the entrance about 15,000 years ago, sealing the cave and its contents until discovery. Over nearly 30 years of excavation and research more than 5000 catalogued specimens have been excavated from only 4% of what is estimated to be a staggering 5,000 tonnes of bone-rich sediment.

The Marsupial Lion Thylacoleo carnifex moves in on a potential meal: the giant marsupial herbivore Diprotodon optatum in a snowy ice-age Plestocene terrain. The bones of Pleistocene animals such as these are found in abundance in the fossil deposits at Naracoorte.
[Reconstruction by Anne Musser]

 

The flat-faced Macropus titan, a now- extinct giant form of the Grey Kangaroo

The Naracoorte fauna includes elements of the extinct Australian megafauna. During the Late Tertiary there was a trend of increasing body size in animal species. The ancestors of modern species were larger then, and some species that are now extinct were very big. Zygomaturus trilobus and the marsupial 'tapir' Palorchestes azael were large marsupial herbivores. They browsed alongside giant kangaroos such as Macropus titan, a giant form of the Grey Kangaroo and Procoptodon goliah, a hoof-toed Giant Short-faced Kangaroo that could reach 3m. Wonambi naracoortensis, a gigantic snake, searched for prey along with Thylacinus cynocephalus, the Tasmanian Tiger, Sarcophilus harrisii, the Tasmanian Devil and Thylacoleo carnifex, the leopard-sized marsupial lion.

Key stages in the evolution of the Australian climate and biota are included in the time span represented by the Naracoorte assemblage, including the period during which humans first arrived in Australia. The continent was becoming increasingly cool and dry, with occasional periods of warmer, wetter climate towards the Late Pleistocene. The dry and wet periods correspond to glacial and interglacial periods respectively on the other continents. These climatic changes, in particular increasing aridity, had profound effects on the Australian fauna and flora. By 15,000 years ago a significant number of large mammal species had become extinct.

 

Pleistocene 300,000 - 15,000 BP
Time line and position of the continents during formation of the Naracoorte Fossil Chamber deposit.
Throughout this period Australia was virtually in the same position that it is in today (red). The continent is still moving northwards and will collide with South-east Asia within the next 30 million years. The Pleistocene Epoch lasted from 2 million years ago to 10,000 years ago.