A red kangaroo’s fore limbs are much smaller than the both the tail and the roo’s hind legs. And that’s the key to the animal’s pentapedal gait.

The red kangaroo has a large body, long powerful hind legs and feet for hopping and leaping, with a long heavy tail used for balance. The kangaroo can leap up to 40' (12 m).

The kangaroo is the only animal that uses its tail in this way, essentially as an extra leg, the researchers said. It's evolved a structure capable of handling the task, they say.

Red Kangaroo – the largest of all, often taller than humans. Eastern Grey Kangaroo – more common and highly adaptable. Western Grey Kangaroo – smaller and very agile.

The length from the red kangaroo's head to its rump is 3.25 to 5.25 feet (1 to 1.6 meters) long. Its tail adds another 35.5 to 43.5 inches (90 to 110 centimeters) to its length and its entire body ...

Figure 1: Pentapedal locomotion in the red kangaroo. Kangaroos moved pentapedally across a force platform (checkered flooring). (a–d) A complete stride starting with contact of the front limbs (t = 0) ...

A red kangaroo mid-stride. Kangaroos are the first known animals to use their tail as a leg while walking. Though larger red kangaroos are known to reach a running speed of some 40 mph (64 km/h ...

The Red Kangaroo is the largest of Australia’s native marsupials. The adult male of the species can grow to about 5 foot, 10 inches tall on its hind legs and weigh about 200 pounds.