Morphological Modifications Page 1

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.

The Wings

Pterosaur wing.
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.



© Patrick Lyons 1998.