Researchers at The University of Queensland, have revealed an ancient and extinct kangaroo fossil, found at the Riversleigh World Heritage Area in north-western Queensland, Australia. The ancient kangaroo fossil defines a new species of extinct, non-hopping kangaroos. 

This new genus is known as Cookeroo, named in honour of a museum researcher, Bernard Cooke. Cooke led most of the research program that focused on the evolution of ancient kangaroo species known as Cookeroo buldwidarri and Cookeroo hortusensis. 

"They lived around 15-23 million years ago and were the size of very small wallabies or pademelons," University of Queensland researchers Kaylene Butler said, according to a press release. The kangaroo species also moved on all four legs and were situated in a densely forested habitat. 

This new found species appears to have also been a direct competitor with a fanged kangaroo species found in Riversleigh. "It seems likely that the fanged cousins were out-competed by our new species and their descendants," said Butler. This may be because the Cookeroo species adapted better to the environmental change, from rainforest to a more open woodland. 

Professors Michael Archer and Suzanne Hand, of the University of New South Wales also contributed to the research and study of the ancient kangaroo species. 

Findings have been published in the Journal of Vertebrate Paleontology.