Homology vs. analogy
The wings of pterosaurs (1), bats (2), and birds (3) are analogous as wings, but homologous as forelimbs. This is because they are similar characteristically and even functionally, but evolved from different ancestral roots.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Homology (biology)."
http://en.wikipedia.org/wiki/Homology_(biology)%23Anatomical_homology
Wikipedia
CC BY.