22 mayo 2015
A unique adaptation in the foot of birds is the presence of a thumb-like opposable toe, which allows them to grasp and perch. However, in their dinosaur ancestors, this toe was small and non- opposable, and did not even touch the ground, resembling the dewclaws of dogs and cats. Remarkably, the embryonic development of birds provides a parallel of this evolutionary history: The toe starts out like their dinosaur ancestors, but then its base (the metatarsal) becomes twisted, making it opposable.
http://feeds.sciencedaily.com/~r/sciencedaily/~3/UepHyjdo6H0/150522174534.htm
