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Flight has evolved three times among vertebrates: Pterosaurs, Birds and Bats. In all three cases it is an example of convergent evolution; all evolved independently of one another. While all three are completely unrelated, they do share some similar morphological features. The reason for this is that the requirements of an aerial existence are high and demand very specific adaptations. Pterosaurs are reptiles and therefore have had to undergo extensive modification of their morphology. The most obvious modification is the change of the forelimbs into wings. There are many modifications and the following pages will discuss some of the more obvious ones. |
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The Wings |
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Pterosaur wing. |
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 © Patrick Lyons 1998. |
The
wings of pterosaurs are membranes of skin that are held out
from the body by an extremely elongated fourth finger. The
bones in the wrist have become fused for added strength and
the hand only comprises four fingers; the fifth having being
lost somewhere on the evolutionary path.
The hand also contains a completely new bone
not found on any other reptiles. The development of a
completely new bone; the pteroid is very unusual and rare in
nature.
