Huge Ancient Kangaroos Walked Instead of Hopping
Posted on October 20, 2014
Modern kangaroos are known for their hopping mode of locomotion. This is also known as pentapedal locomotion. They move using all four legs and their tail. Researchers from Brown University have determined that huge ancient extinct kangaroos, called sthenurines, likely walked around the Australian outback instead of hopping.
Sthenurines were walking around the outback between 30,000 and 100,000 years ago. The researchers say the ancient kangaroo had bigger bones and a stiffer spine than today's kangaroos. Sthenurines grew as tall as seven feet and weighed up to 550 pounds. They also had larger hips, a broader pelvis and bigger knees compared to hopping kangaroos. The broad pelvis would have supported larger gluteal muscles. Another feature that differed in sthenurines were the ankles. The researchers say sthenurines had a flange at the lower end of the tibia that wraps over the back of the joint. Modern kangaroos lack this flange which helps the ankle support greater weight.
The researchers were led by Christine Janis, professor of ecology and evolutionary biology at Brown University. They studied the bones of sthenurines and other kangaroos past and present and made nearly 100 measurements on each of more than 140 individual kangaroo and wallaby skeletons. Janis says the researchers found that hopping would have been difficult for a sthenurine but walking would not have been.
Janis says, "If it is not possible in terms of biomechanics to hop at very slow speeds, particularly if you are a big animal, and you cannot easily do pentapedal locomotion, then what do you have left? You've got to move somehow."
While the biomechanical analysis points toward these ancient kangaroos walking on two feet, Janis notes in a release that it would be helpful to have a discovery like preserved sthenurine tracks to confirm the hypothesis. A research paper making the case for bipedial sthenurines can be found here in the journal PLOS One.
Here is a video that shows the pentapedal locomotion of a modern kangaroo. Take a look: