Skeletal System of an Eastern Gray Kangaroo

Macropus giganteus, the Eastern gray kangaroo, has a skeletal system similar to that of most land-dwelling mammals, with the same bones in the same places. What sets it apart from dogs, humans and deer is, primarily, the relative size of the various bones. The kangaroo's skeleton is specially adapted to suit its lifestyle, with elongated bones in the hind legs and a powerful tail.

  1. Skull

    • The Eastern gray kangaroo has a long, low skull, giving the head its distinctive shape. The powerful jaw is only an inch shorter than the skull itself, and is fitted with two types of teeth: sharp incisors near the tip and rows of molars much further back. Kangaroos will bite to defend themselves against enemies such as dingos.

    Spine

    • Kangaroos have a relatively small rib cage but a long thick spine, terminating in a tail that can reach lengths of up to 4 feet. This tail provides balance when in motion and supports the animal like a tripod when standing upright. Male Eastern gray kangaroos will even balance on their tails while boxing with their hind legs in competition with rivals.

    Arms

    • The forelegs of the Eastern gray kangaroo are much shorter than the hind legs, but are strong enough to support walking on all fours when not jumping. The bones of the forearm, both radius and ulna, are nearly twice as long as the humerus. The paws terminate in five fingers, which can be used to hold objects.

    Legs

    • The hind legs and feet are the defining kangaroo feature; the Macropodidae family is named for their big feet. The tibia is twice the length of the femur, which is little longer than the metatarsals. Though Eastern gray kangaroos are capable of walking quadruped-style, they often jump with their hind legs, reaching speeds of 35 miles per hour, traveling 25 feet with every bound. The legs can be used as weapons as well, due to the long, sharp claws that tip the phalanges.