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Around the world, kangaroos and wallabies are well-recognized symbols of Australia, but a new discovery highlights the deeply linked environmental identities of Australia and New Guinea.

Australian paleontologists from Flinders University have described a new species of fossil kangaroo from central Australia, linking it to the kangaroo tribe of forest-wallabies .

The group of forest-wallabies, called Dorcopsini, had relatives on the Australian mainland around 6 million years ago, according to a patchy fossil record that so far has described two other species of these large wallabies in Australia.

The new species of this "funny little wallaby" has been named Dorcopsoides cowpatensis, due to its bones being found at a location known as Cowpat Hill on Alcoota Station in the southern Northern Territory.

Lead investigator Dr. Isaac Kerr says forest-wallabies probably dispersed into New Guinea from Australia around 12 million years ago and vanished from Australia for reasons yet unknown sometime over the past 5 million years.

"During that time, the islands of New Guinea and mainland Australia were periodically connected by a 'land-bridge' due to lower sea levels, rather than separated by the flooded Torres Strait as they are today. So early Australian mammals moved into the rainforests of New Guinea," says Dr. Kerr, from the Paleontology Lab at the Flinders University College of Science and Engineering.

"When the Torres Strait flooded again, however, these populations of animals became disconnected from their Australian relatives, and so didn't experience the dramatic drying-out that still defines much of Australia."

Dorcopsoides cowpatensis bears many of the features of the living forest-wallabies, but lived in a very different environment, the researchers say. Its home was dry, scrubby bush, with widespread mallee and some denser woodland around ephemeral creeks and lakes.

"This species is thought to have hopped swiftly, but only for short periods, moving from safer dense vegetation into more open areas to feed on leaves, fruits and fungi," says Dr. Kerr.

These prehistoric connections between the more arid Australia outback and New Guinea's wetter, forested and mountainous terrain are seen in the two previously discovered fossil dorcopsins from the upper Miocene in the continental interior and lower Pliocene of southeastern Australia.

This dryland fossil offshoot of these species are part of the primitive group of wallabies called the dorcopsins, with six surviving species found only in the forests of New Guinea.

Professor Gavin Prideaux, co-author of the just published in the journal Alcheringa: An Australasian Journal of Palaeontology, says the forest-wallabies of New Guinea are little known to science, with basic information like diet and habitat uncertain for most of them.

"Living forest-wallabies are cute and peculiar, with slightly sad, whippet-like faces. Their strong, curved tails are used like a fifth limb during slow movement, much like in gray kangaroos, except that the tail arches so only the very tip touches the ground," says Professor Prideaux.

The Flinders University researchers hope that, as they continue to investigate the Australian-Papuan evolutionary interrelationships, they may help to build relationships and connections across the Torres Strait.

"Our research has taken us to Papua New Guinea twice now," explains Dr. Kerr, "and mid-last year we spent weeks digging out marsupial fossils along cliffs over the Watut River in eastern PNG. The university staff and local miners and villagers were immensely warm and friendly and helpful to us.

"The experience demonstrated to me just how much our two nations have in common in the present day as much as in the prehistoric past."