The pterosaurs resembled both birds and bats in their overall structureand proportions. This is not surprising because the design of any flyingvertebrate is subject to aerodynamic constraints. Both the pterosaurs and thebirds have hollow bones, a feature that represents a savings in weight. In thebirds, however, these bones are reinforced more massively by internal struts.
Although scales typically cover reptiles, the pterosaurs probably hadhairy coats. T. H. Huxley reasoned that flying vertebrates must have beenwarm-blooded because flying implies a high rate of metabolism, which in turnimplies a high internal temperature. Huxley speculated that a coat of hairwould insulate against loss of body heat and might streamline the body toreduce drag in flight. The recent discovery of a pterosaur specimen covered inlong, dense, and relatively thick hairlike fossil material was the first clearevidence that his reasoning was correct.
Efforts to explain how the pterosaurs became airborne have led tosuggestions that they launched themselves by jumping from cliffs, by droppingfrom trees, or even by rising into light winds from the crests of waves. Eachhypothesis has its difficulties. The first wrongly assumes that the pterosaurs hind feet resembled a bats and could serve as hooks bywhich the animal could hang in preparation for flight. The second hypothesisseems unlikely because large pterosaurs could not have landed in trees withoutdamaging their wings. The third calls for high waves to channel updrafts. Thewind that made such waves however, might have been too strong for thepterosaurs to control their flight once airborne.
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