TRANSACTIONS OF WAGNER 

 98 



^ UINTA SELENODONTS 



were the most isolated and therefore the most clearly defined of all the seleno- 

 dont families, but such genera as Leptoreodon and Camelomcryx, in which the 

 lower canine has become a functional incisor and the first lower premolar is 

 caniniform (one of the most strikingly characteristic features of the oreodonts), 

 tend greatly to diminish the gap between the oreodonts and the undoubted 

 tylopodans. Even so highly differentiated a type as the White River Proto- 

 ccras is in many respects continues to preserve certain resemblances to the 

 oreodonts. Lcptomcrvx also retains recognizable traces of the same relation- 

 ship, and there is a great deal to be said in favor of the opinion that it was 

 derived from an ancestor in which pj was caniniform. 



If, as Wortman suggests, Bunomcryx represents the transitional stage of 

 dental development for both cameloids and oreodonts, the principal difficulty 

 in the way of connecting the two groups will disappear. This difficulty lies in 

 the uncertainty whether the tetraselenodont upper molar of Frotylopits and its 

 allies was derived from a tooth which retained the anterior intermediate cusp, 

 as is certainly true of the oreodonts. As already pointed out, the asymmetry 

 of tlie upper molars in nearly all of the Uinta selenodonts favors the conclu- 

 sion that they were derived from a type Hke that of Biiuoincryx. 



Another difficulty in the way of referring the oreodonts to the Tylopoda 

 lies in the character of the cervical vertebrae, which in all the genera of the 

 family are short, and show no tendency to assume any of the peculiarities 

 which are so marked in the family Caiiuiidcs, and which are usually regarded 

 as diagnostic of the suborder Tylopoda. These peculiarities are already well 

 defined in the White River genus Poebrothcriiim (though in several respects 

 they are less decided than in the later genera of the line), and it may reason- 

 ably be supposed that in Protylopus also they were present, at least in their 

 incipient stages. However that may be, these features of the cervical vertebrae 

 seem to be confined to the main line of tylopodan descent, the line which in 

 this paper has been designated as the family Camclidce, for in all of the other 

 White River selenodonts {Orcodou, Lcpioiiicryx., Protoceras, etc.) the neck is 

 either short or of only moderate length, and its vertebrae are of the ordinary 

 artiodactyl tj^pe of construction. It is most unfortunate that the structure of 

 the neck is still unknown in all of the Uinta genera except Protoreodon, and 

 hence we are unable to trace the rise and development of the peculiar cameline 

 cervical vertebrae and to determine how early these peculiarities first made 

 their appearance. 



Fi^om the Uinta onward the history of the oreodont family is long and 



