Animals with Limb Variations Skeleton & Superficial Muscles (Side View)

Kangaroo characteristics: Forelimb small; has five digits with strong claws. Large, powerful hind limb with long, strong, narrow foot. Muscular thigh; muscle mass of lower leg positioned on upper half, toward knee. In foot, large fourth and smaller fifth digits transmit force during locomotion; first digit missing, small digits two and three bound together by skin. Long tail, thick at base, used for body support at rest and balance during hopping. Fast locomotion is by leaping with hind limbs only. Walking: Hind limbs, forelimbs, and tail in contact with ground at various times. Sitting: Body rests on entire foot and tail; arms hang loosely. Pouch in female opens forward, supported by two long, thin bones. Sea lion characteristics: Webbed flipper-like forefoot and hind foot. Front flipper thicker on front edge. Skin of flipper extends past tips of toe bones, supported by individual cartilages attached to ends of toe bones. Noticeable claws on three middle toes of hind foot; other claws tiny and inconspicuous. Front flipper triangular; hind flipper rectangular. Hind limb can be advanced forward—can walk, but thigh and lower leg encased in skin of abdomen (seals can’t walk—their hind limbs permanently extended backward). Elbow also enclosed in body skin, but forearms are free. Body streamlined (torpedo-shaped) for swimming. Thick insulating blubber layer between skin and muscles. Thick, flexible, muscular neck. Pelvis and femur small. Sternum has forward projection. Small external ears present (absent in seals). Ears and slit-like nostrils can be closed under water. Short, stubby tail. Very short hair; fur much darker when wet. Body uniform in color (no spots). Males larger than females. Closely related to terrestrial carnivores. Pinniped is not scientific classification, but means “fin footed.”