Giant lions and kangaroos once roamed Australia

Marsupial lions, kangaroos as tall as trucks and wombats the size of a rhinoceros roamed Australia's outback before being killed off by fires lit by arriving humans, scientists said on Thursday.
The giant animals lived in the arid Nullarbor Desert around 400,000 years ago, but died out around 50,000 years ago, relatively shortly after the arrival of human settlers, according to new fossil skeletons found in caves.
Fossilised remains were uncovered almost intact in a series of three deep caves in the centre of the Nullarbor desert - east of the west coast city of Perth - in October 2002. "Three subsequent expeditions produced hundreds of fossils so well-preserved that they constitute a veritable "Rosetta Stone for Ice-Age Australia", expedition leader Gavin Prideaux said of the find, detailed in the latest edition of the journal Nature.
The team discovered 69 species of mammals, birds and reptiles, including eight new species of kangaroo, some standing up to 3 metres (9 feet) tall. Protected from wind and rain, and undisturbed due to their remote location, the remains of the mega-beasts are in near-perfect condition, including the first-ever complete skeleton of a marsupial lion, Thylacoleo carnifex.
"Unwary animals bounding around in the case of kangaroos, or running around in the case of marsupial lions and wombats, fell down these holes, as presumably most were nocturnal. It's very difficult to see a small opening on a flat surface at night," Prideaux said.
Research into the fossils challenges recent claims that Australia's megafauna were killed off by climate change, pointing the finger instead at fires, probably lit by the first human settlers who transformed the fragile landscape.
The lands inhabited by the megafauna once supported flowers, tall trees and shrubs. But isotopes extracted from skeletal enamels show the climate was hot and arid, similar to today. The plants, the scientists said, were highly sensitive to so-called fire-stick farming, where lands were deliberately cleared by fires to encourage re-growth.