The easiest example is of Pentadactyl limbs. This is the 5 bone structure of the 'arm' of different animals being similar, contributing to the explanation of common ancestors. Animals that have this are whales, horses, dogs, cows, birds and even humans. We each share the same five bones in similar places but with some of them changed to suit certain functions ie birds are more spread to support flying, while humans are made for throwing, picking up and holding things.