A team of scientists from the Universities of Queensland and New South Wales and the Western Australian Museum have discovered two new species of extinct kangaroos in our region that could be the ancestors of all modern kangaroos and wallabies in Australia

Western Australian Museum mammals curator Kenny Travouillon said the new species lived about 23-15 million years ago, were the size of small wallabies, and couldn’t hop.

“These kangaroos moved about on all fours, we know they couldn’t hop because their leg and ankle bones aren’t the right shape,” Dr Travouillon said.

“Our research shows that the new species of kangaroos were direct competitors of a second group of kangaroos that also lived at Riversleigh at the same time – the balbarid or fanged kangaroos. It appears the new species survived and their descendants thrived, we believe evolving into the modern hopping kangaroo and wallaby species, while their fanged cousins became extinct.”

Dr Travouillon discovered skulls belonging to the two new species while working with fossil collections at the Queensland Museum and the University of New South Wales.

The new species, which also belong to a new genus of the animals, were described by a PhD research student he was supervising at the University of Queensland, Kaylene Butler.

The new genus has been named Cookeroo in honour of Dr Bernard Cooke, a distinguished Queensland Museum researcher who pioneered work on the evolution of ancient kangaroos.

The two new species within the genus are Cookeroo bulwidarri, which lived about 23 million years ago, and Cookeroo hortusensis, which lived 20-18 million years ago.

The species are named for the areas in which they were found – Bulwidarri means “white” in the local Waanyi language and is named for the White Hunter Site at Riversleigh; while hortusensis is Latin for “belonging to the garden” for Neville’s Garden site.

Dr Travouillon said the discoveries were extremely significant for science because little is known about the evolution of Australian marsupials.

“The fossil record is fairly patchy, featuring a few mammals from about 55 million years ago and then no fossil record until 26-24 million years ago when we see many of the modern families of marsupials as well as a few that are now extinct, so there is a big gap,” he said.

“Our previous records showed the dominant group at that time to be the now extinct fanged kangaroos, and there was also a killer kangaroo, Ekaltadeta ima, which was probably more an omnivore and is related to the musky rat-kangaroo which lives in the rainforests of northern Queensland and cannot hop. Adding the information about the Cookeroo genus helps us flesh out the evolution of this very important, iconic Australian animal.”