II. A NEW TITANOTHERE FROM THE UINTA EOCENE. 

 By O. a. Peterson. 



During the summer of 1912, while collecting fossils for the Carnegie 

 Museum and seeking for data bearing upon the geology of the Uinta 

 Basin, the writer was so fortunate as to find in the upper portion of 

 Horizon B, near Myton, on the Duchesne River, Uinta County, Utah, 

 a number of specimens pertaining to a phylum of the true Titanotheres, 

 The material is new to science, and bears directly upon important ques- 

 tions discussed in his Memoir upon the Titanotheriidae by Professor 

 Henry Fairfield Osborn, now, as we are informed, nearing completion. 

 In order that these additional data may be published early enough to 

 be incorporated in Professor Osborn's work, it has been decided, at his 

 suggestion, to print this paper in the Annals without waiting foi the 

 fuller account of the fauna of the Uinta which is in contemplation. 



In the December issue of the American Naturalist, 1895, the late 

 J. B. Hatcher published a new species of Diplacodon {D. emarginatum, 

 suggesting for his species a new generic name {Protitanotherium) 

 "should futuie discoveries show that there are hornless forms with the 

 same dental character as Diplacodon." Whether or not the true 

 Diplacodon elatnm Marsh^ has horns, is still, I believe, an open ques- 

 tion. Professor Osborn in his "New and Little Known Titanotheres 

 from the Eocene and Oligocene,"^ has accepted Hatcher's proposed 

 genus Protitanotherium without much comment.^ We anticipate that 

 in his forthcoming work he will give his reasons for accepting the genus. 



From the studies of Osborn, Earl, Hatcher, Douglass, and Riggs, 

 we see that the Titanotheres of the Upper Eocene were already well 

 differentiated. In fact it appears that the family had at this time 

 reached its highest polyphyletic development, the survivors in the 

 lower Oligocene being restricted to only those with true horns already 

 developed. As was foreshadowed by Hatcher from the remains 

 which he found in Horizon B ("cornutum beds"), it is now apparently 



1 Marsh, O. C, Amer. Jour. Set. (3), IX, 1875, p. 247. 



2 Bull. Amer. Mus. Nat. Hist., Vol. XXIV, 1908. p. 615. 



3 In a letter from Professor Osborn, dated November 20, 1912, he stated that 

 the true Diplacodon is a slender form, while Protitanotherium is a robust animal. 



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