436 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



nasals of the new species are longer, thinner, somewhat narrower 

 (especially in specimen No. 2859); furthermore the lateral 

 borders of the nasals are much less thickened, and instead of 

 the broadly emarginated area at the free end of the nasals in 

 P. emarginatum, the termination of the nasal of the present 

 form has an abrupt downward turn resembling that of 

 Megacerops coloradensis Leidy, and its anterior margin is very 

 convex transversely, instead of concave, as is the case in P. 

 emarginatum. Upon the whole the nasals of the species we are 



X, 



^^»8««i«^ 



'■'*% 



Figure 365. — Skulls of Eotitanotherium osborni 



[ = fig. 365].) This varied development of the horn cores is no 

 doubt due to se.xual differences, or possibly to individual 

 variation. The premaxillaries extend well in front of the 

 maxillaries and are separated in front, forming a deep median 

 notch, as in P. emarginatum, so that the median pair of 

 incisors are wide apart, while farther back they are firmly 

 coossified and also solidly fused with the maxillaries. The 

 infraorbital foramen is also of large size as in P. emarginatum 

 and located above p^ as in the latter species. The maxillary 

 is on the whole very robust and shows 

 that it had advanced well toward 

 the condition found in Diplacodon 

 and Titanotherium. This is also true 

 of the ]'ugal, the prominent lower 

 border of which has the downward 

 and backward sweep in front of 

 and under the orbit, which is charac- 

 teristic of Titanotherium. The zygo- 

 matic arch, though widely expanded 

 behind, is, however, less robust than 

 in the Oligooene genus and agrees 

 better with the type of Diplacodon 

 elatum described by Marsh. The 

 postorbital processes on the frontal and 

 jugal are of large size, in this respect 

 unlike Titanotherium. The postorbital 

 process on the frontal of the latter 

 genus is usually located farther back 

 and is much smaller in proportion. 

 The external portion of the glenoid 

 cavity is preserved in No. 2858 and is 

 somewhat less convex in the antero- 

 posterior direction than in the latter 

 genus. As in Titanotherium the 

 anterior palatine foramina are small 

 round openings, which in the present 

 genus are situated farther back from 

 the alveolar border of the incisors. The 

 palate is of the deep concave form 

 usually met with in the titanotheres, 

 and the posterior narial opening ex- 

 tends approximately as far forward 

 as in the Oligocene genus, reaching to 

 the posterior portion of m^. 



That the type of the skull was saddle- 

 shaped is very evident from the 

 material under study, but whether or 

 not the characteristically broad 

 superior aspect of the parietals and the 

 heavy and broad occiput seen in 

 Titanotherium had been attained to 

 the same degree as the similarity of 

 the anterior region in the two genera 

 suggests might have been the case will 

 not be completely known until the 

 posterior region of the skull of the Uinta 



After Peterson. One-Iourth natural size. A, Type skull, with associated lower jaw, 9 , Carnegie Mus. 2859, Duchesne representatives of this phylum is 

 River near IVIyton, Uinta County, Utah, Uinta B 2; B, paratype skull, tf , Carnegie Mus. 2858 (reversed), same fo^nd. It is highly probable that the 



locality and level as A. 



describing extend further forward. There seems to be a con- 

 siderable variation in the development fo the horn cores; thus, 

 in skull No. 2858 this protuberance appears to have a develop- 

 ment comparable to that of some of the titanotheres found in 

 the Ohgocene, while in specimen No. 2859 these osseous bosses 

 are very much smaller, more conical, and in proportion more 

 like those of P. emarginatum, in spite of the fact that the skull 

 we are considering pertains to an old individual. (See PI. VII 



similarity presented by the anterior 

 region will be preserved throughout the cranium, which will 

 then reveal more exactly the features of a true titanothere than 

 was anticipated. From the type of Protitanotherium emar- 

 ginatum at Princeton University, Hatcher ^o was apparently 

 able to determine that the sagittal crest is absent and that the 

 dorsal surface of the skull is probably slightly concave antero- 

 posteriorly. 

 !• Am! Naturalist, vol. 29, p. 1085, 1895. 



