"The fossilized remains of giant lions and other ferocious monsters... A wombat — a burrowing, pig-like marsupial that carries its young in a pouch — the size of a mini car and the world's largest kangaroo [10 feet tall] were among the creatures unearthed in caves on the Nullarbor Plain, the vast desert stretching from Kalgoorlie in Western Australia to South Australia's Gawler Ranges."

The article says that the fossils are "believed to be around 1.5 million years old", even though they are still waiting for dating test results, and the arrival of humans 60,000 years ago is offered as one reason for their extinction.

Like many other "bone caves" around the world, we have a bunch of creatures that would never hang out together, all dying at the same time in a mysterious way. Sheltering from a cataclysm is a reasonable possibility for why they were together.