60 Prof. 8. W. WUUston—The Fingers of Pterodactyls. 



and were in life loosely attached by the soft parts only to the 

 •distal part of that bone. 



Recently, in the examination of a specimen of Pteranodon or 

 Ornithostoma, in which all the bones of the hand had been preserved 

 in nearly their original positions, I have observed that these three 

 small fingers have two phalanges in the first, three in the second, 

 and four in the third, the terminal one of each a much curved and 

 sharp claw. So far as I can learn, all known pterodactyls have 

 the same number and arrangement of these bones. In any event, 

 I believe that any possible variation will be found in a lessened rather 

 than an increased number. Seeley (" Dragons of the Air," p. 129) 

 confirms this arrangement of the phalanges in these animals. The 

 patagial finger has, as is well known, four phalanges, probably in 

 all known forms. It seems very probable, however, that in the 

 evolution of this finger for the support of the volant membrane, the 

 original clawed phalange had become lost, not that it had become 

 greatly elongated as the fourth phalange. More especially does 

 this seem probable from the fact that in the later, more specialized 

 forms of these animals there is a marked tendency toward an 

 increase in length of the proximal membrane-supporting bones, 

 and a shortening of the distal ones. In a specimen of RhnmporhyncJius, 

 as stated by Seeley (op. cit.), the first wing-phalange measured 

 3^ inches in length, while the fourth phalange had a length 

 of 2 inches. In a specimen of Pteranodon now before me the 

 proximal wing-phalange measures nearly 27 inches, while the fourth 

 is only a little over 5 inches in length. A still greater dis- 

 proportion exists between the fingers in Rha7nphorhynchus and 

 Nijctosaurxis. Now, if my reasoning is correct, the phalanges in 

 the four definitely known fingers of pterodactyls originally numbered, 

 in succession from the radial to the ulnar side, 2, 3, 4, 5. It is well 

 known that in all reptiles, save the turtles, the anomodonts, and 

 certain extinct hyperphalangic forms, as well as in the birds, this 

 phalangeal formula applies to the first four digits of both the hands 

 and the feet, and it certainly does to the feet of pterodactyls. The 

 conclusion, therefore, seems to me incontestable that the wing-finger 

 of pterodactyls is the fourth, as was formerly held by all writers 

 on these animals. In 1878, however, Oscar Fraas suggested that 

 the so-called pteroid bone really represented the first finger, and 

 that the wing-finger is the fifth. This view was adopted by both 

 Marsh and Zittel, and is the one now universally accepted by 

 palaeontologists. 



It therefore seems evident that the 'pteroid' is not a vestigial, 

 abnormally reflexed metacarpal or phalange of the first digit, but 

 an entirely distinct ossification. Just what this ossification is, 

 it may be premature to suggest, but there is nothing unreasonable in 

 the supposition that it is a carpal or sesamoid. This conclusion seems 

 more probable from the fact that it was progressively developed in 

 the later, more specialized forms reaching its maximum in Nyctosaurus, 

 thereby subserving some progressively increasing functional use, 

 which would hardly be expected were it a reflexed finger. 



