Notice how these tetrapod limbs are similar to one another: They are all built from many individual bones. They are all spin-offs of the same basic bone layout: one long bone attached to two other long bones.
Image use policy: For non-commercial, educational purposes, this image may be used with a Creative Commons CC BY-NC-SA 4.0 license. Please credit as follows: © University of California Museum of Paleontology, Understanding Evolution, www.understandingevolution.org
This image is part of a series: