San Francisco Frontiers - 'Musky' marsupial could solve hopping kangaroo mystery

Kangaroos and closely related wallabies are the only large animals to hop upright on two legs, researchers from Australia's Flinders University said Thursday, but why remains a mystery.

They believe the answer may lie with the small musky rat-kangaroo, a bush-dwelling marsupial weighing about the same as a loaf of bread.

Musky rat-kangaroos are a distant ancestor of the larger kangaroo species that famously roam the country's outback.

Researcher Amy Tschirn said musky rat-kangaroos -- named for their pungent scent -- were the only member of the "macropodoid" family that did not hop.

"As the only living macropodoid that doesn't hop, the musky rat-kangaroo provides a crucial insight into how and when the iconic hopping form of locomotion evolved in Australia."

Scientists tracked the creatures, also known as "muskies", through the tropical rainforests of far-northern Queensland state.

They observed the creatures moving in a "bounding" motion -- hopping with their back legs while their front paws remained on the ground.

It suggested a kind of mid-point in the evolutionary journey from walking on all fours to hopping on two, the researchers said.

"These results signal a potential pathway to how bipedal hopping evolved in kangaroos," said Harvard University biologist Peter Bishop, who was involved in the work.

"Perhaps it started with an ancestor that moved about on all fours like other marsupials, then an animal that bounded like the muskies, and finally evolved into the iconic hopping kangaroos we see in Australia today."

Kangaroos and wallabies are the only hopping species heavier than five kilogrammes (11 pounds), the researchers said.

Some smaller species of rodent also hop.

The researchers said they hoped to find fossils of ancient marsupials to better understand the evolution of modern-day kangaroos.

Their findings were published Thursday in peer-reviewed journal Australian Mammalogy.

X.Roberts--SFF