The Mechanics of Snakes^ 



By Alfred Leutscher 



British Museum (Natural History) 



[With 3 plates] 



A FRIEND of mine once tried to get through the customs a snake he 

 was bringing back with him from the Continent. Four-footed ani- 

 mals, such as the rabbit and squirrel which he also had with his bag- 

 gage, were passed by the customs officer without comment. But no 

 matter how my friend attempted to trace the ancestry of his reptile 

 pet in terms of lost legs, it had none just then, so that was that. 



That serpents are of quadruped descent is not an easy matter to 

 prove. Their lack of legs was formerly sufficient, even among scientific 

 circles, to link them with other limbless creatures, such as those amphib- 

 ians with scales in their skins, called coecilians, and certain limbless 

 lizards like our native slowworm. There is even no tangible evidence 

 to show that they ever possessed fmictional limbs. 



Snakes have been claimed from Cretaceous rocks, but such occur- 

 rence is doubtful. Later fossils from the lower Eocene in America 

 approach the lizard type in bone structure. Viperlike snakes are 

 known from the Miocene of France and Germany. More recent snakes 

 from Egypt are boalike and appear to have been monsters, probably 

 growing to 60 feet in length. All the above were snakes — that is, 

 without functional limbs. 



There is no "story of the horse" flavor to show for a snake's evolu- 

 tion, which is understandable since the skeletons of these creatures are 

 too delicate and brittle to fossilize well, and the full story of how the 

 snakes evolved may remain forever a secret. 



Circumstantial evidence and comparative anatomy of snakes, how- 

 ever, indicate that they are undoubted reptiles which, as a class, are 

 derived from land quadrupeds. A faint clue to the origin of snakes 

 may be seen in the skeleton of the largest living species, which are of the 

 more primitive kind. One familiar member of this family (the Boi- 

 dae) , the python, retains a curious relic of the past in the shape of cer- 

 tain bones lying near the base of the tail. They consist of what are 



Reprinted by permission from Discovery, December 1950. 



303 



