342 



Marvels of the Universe 



Bypy 



11. H. Johnston. 



A PTERODACTYL 



The Pterodactyls were winged reptiles which flourished in the Secondary Epoch. Their wings were not like the wings 

 of birds, but rather lilce those of the bats, a membrane being spread from the body to the greatly lengthened fifth 

 (inger. 



THE PTERODACTYLS 



BY SIR HARRY JOHNSTON, G.C.M.G. 



One of the unsolved mysteries in the evolution of reptiles is the ancestry of the Pterodactyls, or 

 winged Saurians. Though they offer an example of most elaborated development for the special 

 purpose of flying through the air, their fossil forms appear quite suddenly in the rocks dating from 

 the middle of the Secondary Epoch (the Lower Lias). Some features in the skull suggest relation- 

 ship to a primitive order of reptiles, of which the Sphenodon of New Zealand is the only living 

 representative [this order will be illustrated in a later page], and other points in the skeleton recall 

 similar structures in the Crocodiles. The brain and the bones in many particulars offer a striking 

 resemblance to the brain and bones of birds. But this, as so often occurs in Nature, is very mis- 

 leading, being due not to any real relationship, but to similar effects produced by a similar mode 

 of life. The wing in these flying reptiles consists of an immense membrane growing out from the 

 sides of the body and limbs, and depending mainly for support on an extravagant development 

 of the fifth or " little " finger of the hand. This fifth finger, instead of being the smallest in the 

 series as it is in so many land vertebrates, is about six or seven times the length of the other fingers. 

 Three of these {the first, or " thumb," is missing) remain quite outside the wing, instead of being 

 covered by its structure as is the case with modern birds. In complete contrast to the Pterodactyls, 

 the bird's wing consists of very little membrane, its flying surface being made up by feathers — 

 exaggerated scales — which grow from the edges of the flipper formed by the second and third 

 fingers. The Pterodactyls retained four fingers and five toes, but lost all vestige of the thumb ; 



