Fossils of giant animals have been found across Queensland and Australia; however, they are not from dinosaurs or marine reptiles. Palaeontologists call them ‘megafauna’, which simply means ‘giant animal’. Megafauna evolved long after the Age of Dinosaurs in the later part of the Cenozoic Era, from around 15 million years ago until their extinction approximately 40,000 years ago. Unlike dinosaurs, megafauna do not form a singular related group. Instead, megafauna include giant types of mammals, reptiles and birds. Megafauna fossils were first acquired by Queensland Museum in 1862 and many specimens have been discovered since. Queensland’s megafauna include the world’s largest marsupial (Diprotodon) and lizard (Megalania), alongside giant horned tortoises, tree kangaroos, snakes, possums and even frogs.
After the extinction event 66 million years ago the role of the Earth's biggest land and sea animals was left open. Survivors of this catastrophic event included the mammals, lizards, snakes, frogs, crocodiles and the last surviving group of dinosaurs, the birds. Over time, these groups evolved gigantic varieties, called megafauna.
During the Pleistocene Australia's tropical north was dominated by mega-reptiles, including giant crocodiles, lizards, snakes and tortoises. Most of these species were the apex predators on land and in the freshwater rivers, lakes and billabongs. They even dominated central Australia's Lake Eyre when it was permanently full of water.