In 1798 the zoologists of the British Museum in London met to examine the skin of an extraordinary animal, which had been sent to them from New South Wales by a colonist called Dawson. That animal was completely different from anything they'd ever seen before. Its fur was like that of an otter, it had webbed feet like a duck, a flat tail like a beaver and in place of a mouth a duck's bill. Those experts declared Dawson's animal to be an elaborate hoax, but in reality it was just one example of an entirely different wildlife.
Millions of years of isolation had made it possible for a process of parallel evolution to take place in Australia. Ancient groups of mammals who had tried their luck in the fight for survival had almost entirely disappeared from the other continents. While alone on this enormous island in the Southern Hemisphere, they were able to diversify far away from their better equipped competitors.
Australia separated from the rest of the world became a gigantic Noah's Ark, where those original inhabitants of Gondwana, the super continent which contained all the lands of the Southern Hemisphere were able to prosper. Here, life evolved along different lines and the continent of Australia became home to unique zoological species. The fish experimented with lungs. The birds grew to almost two meters, the trees became fire resistant... and the mammals laid eggs.