THE BEGINNINGS OF FLIGHT 



9 



flight. Just such tufts of feathers are 

 known to have occurred in Archceoptcryx 

 (BerUn specimen), and Mr. Beebe con- 

 chides that, Uke the back fins of the fly- 

 ing fish, they served to support the 

 hinder part of the botly as the creature 

 sailed — or as our Enghsh cousins prefer 

 to put it — parachuted through the air. 

 For Mr. Beebe doubts that even Archoeop- 

 teryx was capable of true flight, believing 

 that the fore limbs, like the hind, were 

 rigidly extended at right angles to the 

 body and not flapped. 



A most striking bit of e\idence is the 

 fact that just as o\-erlapping co^•erts 

 are found above the secondaries of the 

 bird's wing and alternately with them, 

 so the bristle-like quills on the thigh of 

 the pigeon are surmounted l)y a series 

 of quills placed precisely like the wing 

 coverts. 



A later stage when there has begun a shortening; iif 

 the tail and concentration of the tail feathers 



The value of any character or piece of 

 evidence does not lie in its size but in its 

 constanc^', or in its apparent relation to 

 other characters, so these little bristle- 

 like feathers of the nestling dove, accord- 

 ing to Mr. Beebe, hint at a time when, 

 as just noted, the;s' ser\ed a useful pur- 

 pose and were sufficiently developed to 

 support, or help support, the hinder por- 

 tion of the body. At this stage in the 

 development of birds, which shoukl be 



somewhere near the lower Jurassic, 

 about seven million years ago, both fore 

 and hind limbs bore feathers; but neither 

 pair of limbs took an active part in 

 aerial locomotion, their fmiction being 

 that of planes, purely passive. This 

 phase of the development Mr. Beebe 

 terms the Tdrapteryx or four-winged 

 stage. At this stage, to quote from Mr. 

 Beebe, "flight was merely gliding, the 

 fingers were too free, the arm bones too 

 delicate, the sternum small or absent, 

 and these facts considered in connection 

 with the small, weak pehis, make it 

 impossible to picture the creature as 

 flying skillfully about. In succeeding 

 generations the pelvic wings would be- 

 come more and more reduced. Having 

 arisen from among the surrounding 

 scales, they had for a time volplaned 

 through the air of early ages, a structure 

 passive and, as future centuries would 

 show, of merely transitory function. 

 Yet they were of tremendous impor- 

 tance in allowing the pectoral scales to 

 develop, to become feathers, and then 

 to assume an importance which was to 

 make the class of birds supreme in the 

 air. Yet the function of the pelvic 

 wings had been so passive and negative 

 that no special muscling had been neces- 

 sary, no increase or coalescence of bony 





^■^^ 



The bird as we know it today, with no trace of the 

 "pelvic wing" except in the very young bird. Dia- 

 grams reproduced through courtesy of the New York 

 Zoological Society 



