Kangaroos Did Not Always Hop?

kangaroos

On Wednesday, scientists who conducted an analysis of the fossilized bones of a group of large extinct kangaroos came to a somewhat startling conclusion. After doing a statistical and biomechanical analysis of the remains, the scientists concluded that the ancient kangaroos likely did not hop.

The group of extinct ‘roos that the scientist studied were ones with relatively short faces and snouts and big bodies. Sthenurines, as they are called, lived in Australia from around 13 million years ago to as recently as 30,000 years ago. Their extinction appears to have roughly coincided with the arrival of the first humans in Australia.

The faces of the kangaroos were similar to those of rabbits. Perhaps the size of them was deterrent enough to make any predators wary and think twice about attacking them. The species called Procoptodon goliah was the largest of the ancient kangaroos who possibly did not hop. These huge animals were around nine tall and three meters in length, weighing in at roughly 500 pounds.

According to a study that the scientists published in the journal PLOS ONE, the scientists noted key anatomical differences between the ancient ‘roos and modern-day ones. They were similar to humans, in that they walked upright and were bipedal. They walked by placing one foot in front of the other, something that modern-day ‘roos just cannot do.

In the words of the study, the ancient kangaroos were “well suited for bearing weight on one leg at a time” but their bodies were not as anatomically suited to hopping.

Besides this important difference in anatomy, the ancient ‘roos also had knee and hip joints that were bigger than those of today’s kangaroos. Their ankle joints were more stable, as well, and they had spines that were simply not made for hopping, ones that were not as flexible as those of kangaroos today. Their tails were likely more rigid, and not used in the same ways that today’s kangaroos use their, sort of like a third leg, to help them balance and stabilize their movements.

The head author of the study, which has the rather inelegant title of “Locomotion in Extinct Giant Kangaroos: Were Sthenurines Hop-Less Monsters?” and was published in PLOS ONE, was paleontologist Christine Janis, of Brown University. She theorized that sthenurines of smaller statures might have walked, in general; but, when greater speed was called for, they might have resorted to hopping.

These findings are preliminary, and further fossil evidence is necessary to confirm them 100 percent. However, the anatomical differences that Janis and the other scientists involved in the study noted when they analyzed the fossilized sthenurine bones seem to point to their having been bipedal, at least at slower speeds.

The ancient kangaroos, known as the sthenurines, probably rarely, if ever, hopped, according to a recent scientific study published in the PLOS ONE journal. Some media wags have said that they were possibly “too fat” to hop, but the real reason they evolved to walk in a bipedal fashion was likely related to their large size and relative lack of predators — that is, up until the arrival of humans in Australia.

Written By Douglas Cobb

Sources:
The Hindu
Weekend Santa Cruz
WallStreetOTC

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