What are the features typical for penguins?

1.The body of the penguin has a streamlined shape and developed muscles of the pectoral keel
2. Penguins cannot fly. Their bones lack cavities that make birds weightless.
3. On land, they either walk vertically on their hind legs, or slide on the snow, lying on their belly, pushing off with all their limbs.
4. The most characteristic external sign of a penguin is the complete absence of flight feathers on the wings, which, in addition, are completely unable to bend