The dinosaurs of Australia disappeared at the end of the Cretaceous, as they did the world over. Their departure marked the end of the supercontinent of Gondwana. By the middle of the Eocene, some fifty-five million years ago, only Australia, Antarctica and South America remained as it straddled the South Pole.
Free of ice and the giant marine and flying reptiles, a new line-up of mammals, flightless birds, crocodiles, snakes and turtles thrived in the warm, wet climate, rapidly adapting and dominating the forests, oceans and skies. New and fanciful creatures, the monotremes, marsupials and placentals explored and took root in the Gondwanan forests as conifers gave way to broad-leaved trees in an ever changing landscape.