the Giant Koala wasn't really all that giant. Fossils demonstrate that the species was about 1.3 larger, but much heavier and more robust. What makes the species really interesting is that they happened to live side by side with modern Koalas. They were not their ancestors, but rather their genus sharing cousins. This brings up questions regarding where Koalas actually came from, as for a long time they were considered to be descendants of the Giant Koalas. So far the fossil record hasn't provided the full picture (which is common, as there are very exact conditions that must be met for something to fossilize).