APPENDIX C 



The Evolution of Whale Tails 



WHILE the evolution of the cetacean tail must remain purely theo- 

 retical until fossil evidence ascertains whether whales are de- 

 scended from terrestrial animals and, if so, by what interm.ediaries, we 

 are entitled to conjecture its beginning with a paddle-shaped rudder like 

 the tail of the living saro, or giant otter, of the Amazon. Starting from 

 this point, we can progress readily via the broad paddle of the beaver, 

 to the virtually circular paddle of the manatee, thence to the tail of the 

 dugong, and from this to the somewhat similar organ of the boutu. From 

 this point onward, the stages of development became various and in- 

 volved. 



It would appear that, while the actual proportionate length of the tail 

 to that of the animals involved — that is to say, the tail proper as defined 

 by the bones of the vertebral column — did not decrease, the side flaps, 

 or paddle blades, or flukes, became progressively shorter from front to 

 back as they became longer and more widely spread to either side. Actu- 

 ally, these flukes retreated progressively along the tail until they ex- 

 tended well beyond its extremity, like the tail fin of a fish. The form, or 

 outline, that they adopted in doing so, however, did not follow a single 

 line of development. 



Examination of a large number of photographs of whales' tails, under- 

 taken during the search for data for this book, brought to light the 

 rather surprising fact that little if any comparative research has been 

 conducted on the form of this organ in the various groups of whales. 

 Further, the shape of the flukes, as displayed in photographs, was very 

 often at variance with the shape shown in hand-drawn text figures in 

 monographs and other precise works, while we could find no record 

 whatsoever of the tail shape of many species. Also, the most cursory 

 review of what photographs are available showed immediately that there 

 is a quite extraordinary amount of variation in the proportions, shape, 

 and size of the tail flukes even within any one species. In fact, this aspect 



