NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN Jl 



U.S.N.M. 

 No. 

 20391 

 Length of lower cheek tooth series, anterior margin of alveolus for 



P3 to posterior margin of Ms 40.3a 



Lower molar series, M1-M3, inclusive 26.1a 



Ml, anteroposterior diameter : transverse diameter of talonid 7.0 : 4.7 



M2, anteroposterior diameter : transverse diameter of talonid 7-9 : 5-6 



Ms, anteroposterior diameter : transverse diameter of trigonid 11.2 : 5.7a 



a. Approximate. 



* Measurements of posterior upper premolars are taken anteroposteriorly across outer por- 

 tion and transversely perpendicular to _ outer margin. Those of upper molars _ are taJcen 

 anteroposteriorly perpendicular to anterior margin and transversely across anterior portion 

 of tooth. 



Discussion. — The specific characters of 0. plicatus are not readily 

 separated from those that have been cited as characterizing the 

 genus, but in size the cheek teeth are slightly larger than in specimens 

 referred to the better-known Protylopus petersoni. 



Genus PROTYLOPUS Wortman, 1898 



Type. — Protylopus petersoni Wortman, 1898. 



Discussion. — Protylopus received marked attention by Wortman 

 (1898) in his diagnosis of the genus and particularly by Scott (1899) 

 in his study of the Uinta selenodonts. The skull, dentition, and other 

 portions of the skeleton of Protylopus petersoni, as far as known, 

 were compared in detail with the Oligocene Poebrotherium. Except 

 in Peterson's 1919 study of the Uinta fauna, however, I find no 

 mention of comparisons made with Marsh's Oromeryx plicatus. 

 Nevertheless, the similarity between the two in almost all details of 

 the teeth is rather striking. The oversight may be due to the fact that 

 the upper molars in all or nearly all the previously known Protylopus 

 petersoni specimens were so badly worn or obscured that details of 

 the pattern could not be readily discerned. Camelid affinities were 

 diagnosed largely from the snout and anterior cheek teeth. It is im- 

 portant to note that the crown view of the upper cheek teeth shown 

 by Scott (1899, pi. 2, fig. 6) is largely incorrect, or does not represent 

 Protylopus. That of the lower teeth (fig. 7) may represent Protylo- 

 pus, but M3 is peculiar and M2 is surely incorrect. Wortman's illustra- 

 tion (1898, fig. 4) of the lower teeth would appear to be more accurate. 



Protylopus may well be a synonym of Or ornery x, as I suspect that 

 additional material from Uinta B will demonstrate, but is tentatively 

 retained as distinct on the basis of the more nearly rectangular ap- 

 pearance of the upper molars and their relatively shorter length 

 anteroposteriorly. Serious doubt may be entertained as to the im- 

 portance of these proportional differences, as material referred to 

 Protylopus petersoni shows rather distinctive variations. 



