Megafauna are big (mega) animals (fauna). These are animals that lived in Australia up to 100,000 years ago. They were at least 30% larger than any of their extant relatives. There is significant dispute as to whether the megafauna became extinct due to predation by humans or due to climate change.
The Diprotodon, the largest marsupial believed to have ever lived, was the first fossil mammal described from Australia in 1838. Fossil Diprotodon skulls have since been found in Bacchus Marsh, and are currently on display at Museum Victoria.