266 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Pantodonta, respectively, but these names have not been generally 

 accepted. 



The classification thus achieved is well summed up by Osborn (1898): 



Order Amblypoda: 



Suborder Taligrada: 



Periptychidae. 



Pantolambdidae. 

 Suborder Pantodonta: 



Coryphodontidae. 

 Suborder Dinocerata: 



Bathyopsidae. 



Uintatheriidae. 



This arrangement is now classic and with sUght modifications has 

 since come into all but universal use. Nevertheless, in the hght of 

 later discovery and research, it has little to recommend it. 



The probable affinities of the periptychids with the condylarths, 

 rather than with the pantolambdids, have been discussed on a pre- 

 vious page. On the other hand, all recent work (see especially Simp- 

 son, 1929d, and Patterson, 1934) tends to emphasize the essential 

 unity of Pantolambda and Coryphodon and their respective allies. 

 The known pantolambdids are not ancestral to the known corypho- 

 donts, and family separation is warranted, but they are so similar in 

 structure aside from primitive or progressive features generally cor- 

 related with greater or lesser age that there seems no reason to place 

 them in separate suborders, and the distinction between Taligrada 

 and Pantodonta is unwarranted. 



The uintatheres, on the contrary (Simpson, 1929d and elsewhere), 

 seem to be a group independent of the pantolambdids and cory- 

 phodonts from a very remote time and Hnked to them only through a 

 prot- or perhaps even pre-ungulate, non-"amblypod" ancestry. The 

 classic arrangement was undoubtedly influenced by the belief that 

 taligrades, pantodonts, and dinoceratans represented oft'shoots of a 

 single stock appearing successively in time with correspondingly 

 progressive specializations. Now it is clear that this simple picture 

 does not correspond to the facts. Among the supposed "taligrade" 

 periptychids the more advanced members are the only ones that 

 show any considerable resemblance to the pantolambdids in foot 

 structure, but they cannot possibly be ancestral to the latter not only 

 because they are contemporaneous but also because aside from the 

 feet (and in part including them) their structure is very different. 

 The idea of successive offshoots does apply to the pantolambdids and 

 coryphodonts, but it decidedly breaks down again with the cory- 

 phodonts and uintatheres because these groups are not successive but 

 contemporary phyla, and it is the latest and most advanced members 

 of each that show some resemblance, which hence is only convergent, 

 and the earher members are even more decisively dissimilar. 



