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AN INTRODUCTION TO ZOOLOGY 



were fairly large, and the strong jaws were well armed with teeth. 

 While some of them were no larger than a sparrow, others reached a 

 large size, even as much as 27 feet across the wings, and so they must 

 have presented a truly terrific aspect well justifying their popular 

 name of " flying dragons." 



Again, the common Ornithischian stock probably gave rise to 

 the true birds. The forerunner of the Class Aves was a remarkable 



FIG. 178. Reptilian bird, Arch&opteryx (A), compared with pigeon, Columba 

 livia (B). After Lull. 



creature that is found in early Jurassic times and known as Archce- 

 opteryx. Two fairly complete skeletons of this animal are known, 

 but we have no indication of its exact derivation. It was bird-like 

 in many respects, such as the general shape of the body, the feet, and 

 the possession of quite typical feathers and true wings. On the 

 other hand, it had also distinct Dinosaur affinities, which mark it off 

 sharply from modern birds. Thus it had a long pointed tail, short, 



