Marsupial Lion Among Finds in Treasure Trove of Fossils in Oz

The animal was 9ft long, and probably the most fearsome predator on the continent. But the marsupial lion may have been wiped out in Australia by the arrival of humans 50,000 years ago, according to a first analysis of a treasure trove of fossils unearthed in southern Australia. The discovery has been described by scientists as the "find of the century".

"They constitute a veritable Rosetta stone for ice age Australia," said Gavin Prideaux, a palaeontologist at the Western Australia Museum, who led expeditions to recover and study the fossils. "We discovered 69 species of mammals, birds and reptiles, including a remarkable eight new species of kangaroo, the most common of which sported unusually large brow ridges."

The animals are thought to have fallen into the underground caves in the Nullarbor plains between 200,000 and 800,000 years ago, through narrow, 20 metre-long openings. Little is known about Australia from this period, known as the middle Pleistocene.

The hundreds of fossils were extremely well preserved. "Animals wander into these caves and then die - their remains are not subject to the normal rigours of fossilisation," said Norm McLeod, head of palaeontology at the Natural History Museum in London. "They simply dry out, the flesh rots away and you're left with the skeletons."

Scientists published the first analysis of the fossils today in Nature.The most impressive find was the first complete skeleton of the marsupial lion, Thylacaleo carnifex. "We didn't have a complete skeleton of that animal at all until we made that discovery; now we have dozens," said Bert Roberts of the University of Wollongong, who helped to date the bones.

The marsupial lion, which raised its young in a pouch like modern kangaroos and wallabies, would have been the biggest predator on the Australian continent in its prime.

The kangaroos discovered included several species that are now extinct; some had small horns, while others looked as if they lived in trees.

The fossils may shed light on an enduring mystery - why so many species of large mammals suddenly died out around the world 100,000 years ago. There are two prevailing theories behind the disappearance - either natural climate change made Australia too dry for mammals to survive or the arrival of humans somehow upset the regional ecosystem.