The two species that I selected for my homologous trait are dolphins and humans. Although these two seem to appear different and live in completely different settings, they both share a similar homologous trait and a common ancestor. Humans and dolphins both share the same bone structure including the formation in their extended limbs. Although one would not even consider a dolphin's flipper and human's arm to have any similarities, with further examination, one is able to see the similarity homologous traits. The similar traits that exist in the limbs of a human and dolphin include the carpals, phalanges, ulna, radius and the humerus bone fragments. Anyone can distinguish the fact that their is a difference in size and also the shape between the two. The reason for that is that they both live in different environments and use the functions of each of their limbs in different ways and different methods. Dolphins use their flippers for steering through the water and making sharp turns. In order to turn fast they use their back flipper because that helps push them forward. Their use of flippers is also used as communication be being able to touch and feel other dolphins. Humans on the other hand, also use their hands for many different tasks, (which everyone knows how). We use our hands and arms to eat, drive, write, drive and many other common tasks. Their common ancestor will be a mammal, the reason for this is that all mammals share similarities in limb structures.