Stop the hop: for huge ancient kangaroos, hopping was dicey

An artist's rendering shows a big-bodied, short-faced kangaroo called a sthenurine that lived in Australia from about 13 million years ago until about 30,000 years ago. Photo: Reuters 

 

WASHINGTON — Kangaroos hop, right? Well, not all of them.

Scientists said yesterday (Oct 15) that a biomechanical and statistical analysis of fossil bones of a group of huge extinct kangaroos shows that the largest of the bunch in all likelihood could not hop as their modern-day relatives do with aplomb.

The study focused on a group of big-bodied, short-faced kangaroos called sthenurines that lived in Australia from about 13 million years ago until about 30,000 years ago, disappearing after the first humans arrived on the continent.
These kangaroos were more heavily built than modern ones and had faces reminiscent of a rabbit. The largest, a species called Procoptodon goliah, weighed about 240kg, stood 2m tall and was 3m long.
The study found important anatomical differences in sthenurines’ limb bones compared with other kangaroos.
In terms of locomotion, they were unlike today’s kangaroos, with an anatomy ill-suited for hopping. They likely walked in an upright bipedal stance — putting one foot in front of the other, just like people — in a way modern kangaroos cannot, the study found.
This was facilitated by larger hips and knee joints as well as stabilised ankle joints unlike today’s kangaroos but like animals that walk or run. They also had a relatively inflexible spine not conducive for hopping.
“Today’s kangaroos mostly use hopping as their fast gait — although tree kangaroos rarely hop. But for slow speeds they use a type of ‘pentapedal’ walk, using all four legs and the tail,” said Brown University paleontologist Christine Janis, who led the study published in the scientific journal PLOS ONE.
With their stiff backs and specialised hands, this “pentapedal” gait would have been difficult for sthenurines. They also lacked certain specialised anatomical features of modern large hopping kangaroos, the researchers said.
Professor Janis said she suspected smaller sthenurines used bipedal walking at slow speeds and may have switched to hopping at faster speeds. “But the largest ones may have walked rather than hopped most if not all of the time,” Prof Janis said.