This undated photo provided by the University of New South Wales is a skull fossil of a flesh eating kangaroo

Scientists in Australia have found fossils of flesh-eating kangaroos and ancient tree-climbing crocodiles.   These bizarre animals inhabited the continent up to 20 million years ago.  The remains of at least 20 previously unknown species were found in the northern Australian state of Queensland. 

Paleontologists uncovered some of unusual treasures at the famous Riversleigh fossil fields in northwest Queensland.

Among others, they found evidence of a saber-toothed kangaroo and a giant bird they nicknamed the "demon duck of doom."  It would have been more than three meters tall and weighed around 400 kilograms.

Professor Mike Archer, who led the team of fossil hunters, says they made some extraordinary discoveries.

"One of the ones that sort of was most amazing to us was a range of kangaroos," said Mr. Archer.  "There are weird, flesh-eating kangaroos. None of the kangaroos, and there are about 35 different kinds of extinct kangaroos in these deposits, none of them would've looked like anything we would have recognized today, because they didn't hop, these were galloping kangaroos, with big powerful forelimbs, some of them had long canines like wolves."

Other discoveries include the remains of marsupial lions, which carried its young in a pouch, and tree-climbing crocodiles.

Paleontologist Sue Hand says the researchers unearthed some frightening specimens.

"Some very large crocodiles, and also very, very big birds, some of these things are called thunderbirds, and they were very big, you know, some of the biggest ever found in the world," she noted.  "And the ones that we found at Riversleigh include things that would've been about 200 kilos or more."

The Riversleigh fossil area was listed as a World Heritage site in 1994. Tucked away in a remote corner of the Australian outback, it is one of the world's most impressive fossil sites.

The scientists say the finds will give great insight into the evolution of many of Australia's unique animals, including the strictly vegetarian kangaroos of today.