An ancient, tough little wallaby set the stage for kangaroo bounding success, research found.

Flinders University paleontologists have found more clues about why kangaroos and wallabies have endured to become one of the continent’s most prolific marsupial groups. They have analyzed the powerful limbs of ancient Australian “true” kangaroos—the common ancestors of modern kangaroos and wallabies.

The paleontologists focused on the limb bones of the extinct Dorcoposides fossilis, found only in the Alcota Fossil Field in the southern Northwest Territories.

Lead investigator Dr Isaac Kerr says these hardy-hopping marsupials, which lived around 7.7 million years ago during the late Miocene, are part of a group known as forest wallabies or Dorcosini.

Although restricted to New Guinea today, the dorkpson had relatives on the Australian mainland by about 5 million years ago.

“When first described in 1967 from some partial jaws, teeth and foot bones, it has since received minimal attention despite the collection of many more specimens,” says Dr Kerr, from the Palaeontology Lab at Flinders University’s College of Science and Engineering. Royal Society Open Science.

“For the first time we have analyzed all their fossil limb bones and compared them with the limbs of (extant) species, to shed light on kangaroo evolution.”

Macropodine kangaroos are those in the subfamily Macropodinae, which includes all living kangaroos and wallabies except one (the banded wallaby).

Between 11 and 7 million years ago, central Australia lost its rains and became increasingly arid. This triggered an evolutionary radiation in macropodian kangaroos, with many new species evolving to exploit the new dry, open habitats.

“During this period, macropodines became a dominant feature of the Australian landscape, which they still are today. However, until this study of Dorcapsidus fossilis, we have no fossil evidence for the evolution of their famous hindlimbs during this period,” explained Dr Kerr.

“Although D. fossilis is generally similar to resident forest wallabies, it has some special features – shown in – for example – gray kangaroos, which means strength and some ability to hop efficiently. These features indicate that the species was partially adapted to move in open habitats, able to move efficiently to find food in dry landscapes.”

This is the first direct evidence of adaptation to open, more arid environments in kangaroos from this time, co-author Professor Gavin Pardo added, adding, “This is evidenced from recent fossils and from genetic analyzes of the timing and nature of the rise of macropodines.”

As far as De Fossilius could have seen, Dr. Kerr says, “Living forest wallabies are strange, with slightly sad, whippet-like faces. During slow movement the arch of their strong, curved tails barely touches the ground. Dorcopoides fossilis probably looks like a larger, elongated version.”