460 LAND MAMMALS IN THE WESTERN HEMISPHERE 



retaining in dentition, limbs and feet so many characteristics 

 of the former. 



fCondylarthra were probably present in the lowest 

 Paleocene (Puerco stage), but the material so far obtained is 

 so fragmentary that there can be no certainty on this point. 



It is not at all probable that any of the North American 

 fCondylarthra should be regarded as ancestral to any of the 

 more advanced ungulate groups ; on the contrary, they would 

 appear to have come to an end in the Wind River, leaving no 

 descendants behind them. It is further true, as was men- 

 tioned above, that the presence of fCondylarthra in other 

 continents, while very probable, cannot be positively asserted, 

 because the evidence is incomplete. Yet it would be a great 

 mistake to assume, for this reason, that these most primitive 

 of ungulates were devoid of evolutionary importance and 

 interest. As is so often the case, where, in the absence of the 

 direct ancestry, the collateral relations afford very valuable 

 information as to the course of descent and modification, the 

 fCondylarthra throw useful light upon the origin of the 

 ungulate groups. It is extremely probable that the fcondy- 

 larths, or some very similar series of primitive hoofed mam- 

 mals, had a very wide and perhaps cosmopolitan range at the 

 end of the Cretaceous and beginning of the Tertiary period, and 

 that, in the still unidentified region, where the artiodactyls and 

 perissodactyls arose, it was from a condylarthrous ancestry. 

 Possibly, all the other ungulate orders may yet be traced back 

 to the same stock, but it is rather more likely that the ungulates 

 include several series of quite independent origin. At all 

 events, it is quite certain that the clawed mammals long ante- 

 dated the hoofed types and that the latter arose, either once or 

 at several separate times, from the former. The fCondy- 

 larthra show how one, at least, of these transitions was effected, 

 and thus, in principle, how all were accomplished. 



