Varanus priscus, more commonly known as Megalania or the giant ripper lizard, was a type of giant monitor lizard and was the largest terrestrial lizard and the largest venomous veterbate to have ever lived. It was a top predator in Southern Australia, and would have probably preyed on large marsupials and flightless birds. It would have had frequent competition with Thylacleo, the marsupial lion, which lived in the same area at the same time.