Editing Forelimb (section)

=== Wings ===
All tetrapod forelimbs are homologous, evolving from the same initial structures in [[Sarcopterygii|lobe-finned fish]]. However, another distinct process may be identified, [[convergent evolution]], by which the wings of [[bird]]s, [[bat]]s, and extinct [[pterosaur]]s evolved the same purpose in drastically different ways.<ref name=":1">{{Cite web|url=https://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_09|title=Homologies and analogies|website=evolution.berkeley.edu|access-date=2019-12-09}}</ref> These structures have similar form or function but were not present in the [[Most recent common ancestor|last common ancestor]] of those groups.

Bat wings are composed largely of a thin membrane of skin supported on the five fingers, whereas bird wings are composed largely of feathers supported on much reduced fingers, with finger 2 supporting the [[alula]] and finger 4 the primary feathers of the wing; there are only distant homologies between birds and bats, with much closer homologies between any pair of bird species, or any pair of bat species.