760 



ARTIODACTYLS 



parallel to that found in Cervidae. The exact origin and affinities of 

 the family remain uncertain. 



12. Antilocapridae and Bovidae 



The remaining Pecora are all rather alike and are often placed in a 

 single family, Bovidae. However, the prong-buck, Antilocapra (Fig. 

 507) of the North American west, and its numerous fossil allies, all 



New World forms, have been distinct 

 since before the Miocene from the true 

 bovids, evolving in the Old World. The 

 origin of the two groups is obscure and 

 we have no Eocene or Oligocene fossils 

 that are certainly on the bovid line 

 of evolution. As already mentioned 

 *Archaeomeryx and other Eocene tragu- 

 lines show us a type of population from 

 which the Pecora could all have been 

 evolved, but the stages of the transforma- 

 tion have not been found. 



Antilocaprids and bovids are alike in 

 living in herds and in their grazing habits, 

 with which are associated deeply hypso- 

 dont molars. The side toes have been almost or completely lost, a de- 

 velopment occurring parallel to that of the cervids, since the common 

 ancestry almost certainly possessed lateral toes, which are indeed 

 present in rudimentary form in some bovids. In Antilocapra (Fig. 507) 

 the horns, present only in the males, are two-branched and have a bony 

 core and rather soft keratinous covering, the latter but not the former 

 being shed. This therefore suggests how a skin-covered antler, such as 

 that of the Cervidae, may have become converted into the bovid horn. In 

 earlier antilocaprids, such as the Miocene *Merycodus, the horns were 

 more elaborately branched; evidently the group has developed a horn 

 structure parallel to that of the Cervidae. In all true bovids the horns 

 are permanent coverings for the bony core. They are unbranched, 

 though curved and twisted in various geometrically interesting ways. 

 Moreover, they are usually borne in both sexes (though often larger 

 in the male) and their function is definitely defensive, as well as social 

 and sexual. Correspondingly the social organization is often into large 

 herds, rather than into the small family groups under a dominant stag, 

 such as are found among Cervidae. Grazing on open plains and 

 mountains has presumably led to the formation of the larger herds, 



Fig. 507. Prong-buck, Antilo- 

 capra. (From a photograph.) 



