A giant dragon capable of killing a rhinoceros is related to the world's largest living lizard, scientists have discovered. The 23ft Megalania prisca, or ancient giant ripper, lived in Australia nearly 20,000 years ago. It was the largest lizard to have stalked the Earth, weighing more than two tons and it has now been revealed as an ancestor of the Komodo dragon which roams the planet today. Scientists believe that the massive lizard was a scavenger and ambush predator.