174 MAMMALIAN DENTITION 



line of development and this family arose imperceptibly from 

 ancestral Creodonts during the upper Eocene. Almost as old 

 though not so clearly denned in origin the Civets also developed 

 in the upper Eocene. In the Oligocene the Cats appeared with 

 shortening of the skull, increase in the size of certain teeth, 

 and reduction in their number and cusps. At this time also 

 we find the earliest Weasels in which again the skull was 

 shortened. From the Dogs in the lower Miocene originated the 

 Eaccoons and in the upper Miocene the Bears, in both cases the 

 teeth increasing in complexity. Lastly the Hyaenas differen- 

 tiated in the lower Pliocene, probably from the Civets. It is 

 therefore most instructive to take up the consideration of these 

 families with the origin of each in mind. Animals which are 

 solitary rather than gregarious naturally will leave fewer fos- 

 silized traces of their existence and hence the history of the 

 Carnivores is not known with the same precision as that of the 

 Ungulates: indeed it is only in the Dogs that the ancestry 

 can be traced back to its inception without a break. In each 

 family progressive features have appeared with change in 

 habits and these have occurred along parallel lines as in other 

 orders. In the chapter on the Primates we have devoted con- 

 siderable space to the study of parallelism in evolution. We 

 must therefore be content simply to outline the general fea- 

 tures of the existing Carnivore families. 



First then we take up the Canidae: the Dogs Wolves and 

 Foxes. Of these the Dogs and the Wolves have very similar 

 dentitions although the domesticated Dogs are less purely 

 flesh-eaters than the Wolves: the Fox dentition is easily dis- 

 tinguished. Dogs of the middle Pliocene possess skeletons 

 scarcely distinguishable from those of today and so far back as 

 the middle Miocene the differences are very small. The fore- 

 runner of the Canidae in the lower Miocene does not differ 

 greatly from the modern Wolf. But the lower Oligocene an- 

 cestor shows so many feline features as to render it probable 

 that here we have the commencing divergence of the Cats from 

 the Dogs. 



