The key features of a penguin's skeleton are its flattened bones and a joint that holds the elbow and wrist together, according to Penguins World. Penguins' forelimbs have developed into flippers that are shaped like small paddles. These are used to allow penguins to swim fast without getting tired.
Penguins World states that a penguin's body is tapered at both ends, allowing it to glide through the water easily. Penguins have large heads and long bodies, and the proportion of their heads to their bodies helps them navigate in the water. The feathers on their flippers are quite short, which helps prevent them from drowning, prevents the water from penetrating their skin and keeps them warm. The feet and legs of penguins are set far back from the rest of the body to maintain balance and to help them walk upright on land. Penguins also have claws on the bottom of their feet. Some penguin species slide on their bellies when attempting cross icy land, as they can move much more quickly this way.
Another aspect of penguin anatomy is the bill, which varies based on each subspecies' eating habits, according to Penguins World. Penguins that feed on krill have short, wide bills, while those that mainly eat fish have long, narrow bills.