CREATION BY EVOLUTION 



merely reptiles that were especially adapted to aerial naviga- 

 tion. Nature essayed this adaptation twice with the reptiles, 

 one product being the pterodactyls or winged reptiles of the 

 Mesozoic era. The pterodactyls and the birds have much in 

 common, even to certain minute details of pneumatic bones 

 with comparable openings of communication one with 

 another: lightness of skull, with a precocious consolidation 

 of cranial bones, and loss of teeth and their replacement by 

 a beak in later forms. The marked distinctions lie in the 

 mechanism of flight — ^by wing feathers in the birds and by a 

 bat-like wing membrane in the pterodactyls. The two groups 

 are doubtless derived from the same or a related non-flying 

 ancestry, and much of their similarity is probably due to 

 community of habit and its reaction on the mechanical struc- 

 ture. 



The links leading to the pterodactyls are still unknown, 

 for our first fossil record of these creatures are the remains 

 of forms that had already attained sustained flight; of the 

 first steps in that direction we have no direct knowledge. 

 Not all conditions of life, however, are equally susceptible 

 of preservation in the fossil record, and this is particularly 

 true of flying forms, for a prerequisite to fossilization is 

 complete burial either in water-borne or air-borne sediments, 

 such burial as befalls flying forms only in very exceptional 

 circumstances. A single locality, a quarry near Solenhofen, 

 Bavaria, worked commercially for limestone used in the art 

 of lithography, has given us nearly all the flying creatures 

 of Middle Jurassic age that we know. Here are pterodactyls, 

 some of which have the delicate wing membrane preserved 

 in perfect detail; but these are already highly specialized 

 fliers. Here also are the first known birds, feathers and all, 

 and among the whole list of connecting links known to us 

 none is perhaps more satisfying. Three individuals are rep- 



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