A long, long time ago, marsupials the size of small trucks, 2-meter-tall "thunder birds" and 5-meter-long venomous lizards roamed Australia. These animals—and more—were Australia's megafauna.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Australia was once home to a group of extraordinary animals known as Megafauna. What became of them ...