338 



TITANOTHBRES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Bridger formation, but the type specimen may have 

 been found in Bridger D. A maxilla discovered by 

 the Princeton expedition of 1877 in Bridger C or D 

 was considered by Scott and Osborn to represent a 

 new genus of animals, to which they gave the name 

 Leurocephalus, the type being the species L. cultridens ; 

 but in 1891 Earle pointed out that Leurocephalus is 

 generically identical with Telmatherium. All the 

 exploration of many subsequent years in the Bridger 

 Basin has not revealed anything certainly similar to 

 these types. In the upper deposits of the Uinta 

 Basin (Uinta C or true Uinta formation) Peterson, of 

 the American Museum expedition of 1894, secured a 

 fine skull of a female specimen to which the name 

 Telmatherium ultimum has been given; and in the same 

 deposits was found the anterior portion of a male skull 

 of the same species (fig. 297). These skulls fortunately 

 throw a flood of light on the cranial structure of these 

 animals, which were previously Ivnown only by upper 

 and lower jaws. 



These animals reappear (Riggs, 1912.1) in the up- 

 permost levels of horizon B 1 of the Uinta Basin (in 

 the " Metarhinus sandstones"), and in the middle of 

 horizon Uinta B 2 Douglass discovered in 1908 the 

 type of T. incisivum to which Gregory (1912.1) gave 

 the name Sthenodectes, a telmathere with very large 

 incisor teeth. 



Finally a large jaw was found by Peterson in 

 Uinta C which apparently represents the latest known 

 member of this series, to which the name T. altidens 

 has been given by Osborn. 



Irregular geologic distribution. — It is important to 

 note that these animals appear simultaneously with 

 the first species of Mesatirhinus and Manteoceras in 

 the upper Bridger levels; that they have not been 

 recorded thus far in the Washakie Basin levels nor 

 in the lower levels of the Uinta Basin; and, finally, 

 that they are sparsely found in the upper or true 

 Uinta levels. As above intimated, this rarity of geo- 

 logic distribution appears to prove that they dwelt 

 apart or in another food region and rarely invaded 

 the region inhabited by Manteoceras and Mesatirhinus. 



General structure and habits. — Little can be said re- 

 garding the general proportions of these animals until 

 the skeleton has been discovered. The known indi- 

 viduals of T. cultridens somewhat exceed in size the 

 largest tapirs, T. validum is somewhat larger, and 

 T. ultimum of Uinta C is still larger, having a skull 

 about 20 inches long. In divergent adaptation the 

 telmatheres were probably swifter and of more grace- 

 ful build than Palaeosyops and Limnohyops. The 

 incisor, canine, and grinding teeth are much more 

 elevated, sharp, and trenchant (hence the specific 

 name T. cultridens) than in Palaeosyops and were 

 reinforced with distinctly defined cingula. 



Phyletic affinities of the telmatheres. — The first ques- 

 tion that arises is, Are these animals more closely 



related to Limnohyops, to Palaeosyops, or to Manteo- 

 ceras? The answer in brief is that although they are 

 somewhat intermediate in position they are related 

 by most of their ancestral or hereditary characters to 

 Limnohyops and Palaeosyops. This real ancestral 

 affinity was long obscured by the general mesatice- 

 phalic character and correlations of the different parts 

 of the skull, jaws, and teeth in Telmatherium, which 

 are the dominant distinguishing features of this 

 animal. 



Affinities to the Palaeosyopinae. — The ancestral affin- 

 ities of the telmatheres to the Palaeosyopinae are indi- 

 cated (1) in the transversely subconvex contour above 

 and in front of the orbit, correlated with the very 

 retarded development of the frontonasal horns {T. ulti- 

 mum); (2) in the subrectangular, rounded rather than 

 shelf -like section of the malars below the orbits; (3) 

 in the deep, laterally compressed form of the zygo- 

 matic arches and the progressive development of a 

 vertical flange {T. ultimum); (4) in the tusklike en- 

 largement of the third or outer superior incisors; (5) 

 in the rounded rather than angular posterior borders 

 of the temporal fossae {T. ultimum); (6) in the ele- 

 vated and rounded superior contours of the occiput 

 (T. ultimum); (7) in the absence of distinct lateral 

 occipital pillars above and on either side of the fora- 

 men magnum {T. ultimum); (8) in the presence of two 

 facets for the atlas just above the foramen magnum 

 (T. ultimum); (9) in the shape of the base of the 

 skull, which is sub-brachycephalic or mesaticephalic, 

 perhaps the strongest indication of affinity with the 

 Palaeosyopinae. The concurrence of these resem- 

 blances in so many different parts of the skull is strong 

 evidence of a community of descent; moreover, the 

 species Limnohyops monoconus exhibits several char- 

 acters that are seen also in Telmatherium — (1) the 

 very high, rounded occiput, with thin sagittal crest; 

 (2) a deep superior flange on the squamosal portion of 

 the zygoma; (3) a similar, though less quadrate infra- 

 orbital portion of the malar. 



Comparative indices in telmatheres and related species 



Influence of dolichocephaly. — It appears that the 

 Telmatherium craniurri is a partly elongate or drawn 

 out Limnohyops type of cranium, and that correlated 

 with this incipient dolichocephaly are the beginnings 

 of numerous familiar dolichocephalic characters; but 

 this incipient dolichocephaly affects chiefly the facial 

 and midcranial regions, while the base of the cranium 



