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.

Carbon-dating teeth suggests two large mammal species roamed northeastern Brazil 3,500 years ago Geologist Fábio Faria and colleagues carbon-dated eight fragments of megafauna teeth of different ...