Kangaroo relative may have walked around ancient Australia on two feet

A giant kangaroo relative that lived 100,000 years ago may have used its hind two legs for walking, not hopping, according to a new study.

And by “walking,” the authors of the paper mean real bipedal walking -- upright, on two feet. Kind of like you and me, except perhaps more bow-legged.

These rabbit-faced kangaroo cousins, which went extinct about 30,000 years ago, must have been pretty imposing. The largest members could grow up to 7 feet tall and weighed up to 530 pounds.

“I think it would have been pretty scary,” said Christine Janis, a professor of ecology and evolutionary biology at Brown University and the lead author of the study. “I can’t imagine them being cuddly.”

In a paper published Wednesday in PLOS One, Janis provides several anatomical lines of evidence to show that members of the extinct kangaroo sub-family called sthenurinae probably employed a bipedal walking gait, in addition to hopping. She also argues that some of the largest members of the group could probably not hop at all -- they would have been too heavy.

Even modern-day kangaroos don’t hop exclusively. They hop to cover long distances, but when they forage for food on the ground they are more likely to use a pentapedal walk, putting all four feet on the ground and using their tail as a fifth limb to propel them forward.

This posture, however, requires a flexible back, something sthenurines did not have. Janis also notes that these ancient creatures had different ankles, pelvises and knee joints than the ancestors of modern kangaroos.

“No one feature is the absolute key,” said Janis. “It’s like looking at a jigsaw puzzle, and the bipedal walk is the best way to explain how the pieces fit together.”

Janis said the animals’ upright stance may have helped them to reach for the leaves and shrubs that made up their diet. They also had a very elongated third and fourth finger and greater range of movement in their arms than modern-day kangaroos. This could have allowed these large beasts to reach into bushes and pull food toward their mouths.

Janis said she may be able to test her hypothesis sometime soon. Researchers have found preserved tracks of other animals that inhabited the same era of Australia’s history.

“If we could find some made by sthenurinae, that would really help our story,” she said.

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