352 



TIT.USrOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



teeth distinctly suggest the upper median incisors of 

 T. ultimum. The laterally compressed or convex 

 anterior faces, the smoothly sloping posterior faces, 

 the U-shaped posterior cingula also suggest the Pal- 

 aeosyops type of tooth, although this dolichocephalic 

 animal does not appear to present any affinity to that 

 genus. It is difficult to determine the precise form 

 and proportions of the canines, the fang measure- 

 ments (vert. 76 mm., estimated; ap. 31; tr. 26) 

 indicating a more laterally compressed or dolicho- 

 cephalic type of canine than in Protitanotherium emar- 

 ginatum. The height of this tall and slender canine 

 exceeds 76 milHmeters (estimated), as compared with 

 53 in the male P. emarginatum and 56 (estimated) in 

 the male P. superhum. The name T. altidens refers 

 to this feature, as the tusk is the most elevated and 



Figure 299. — Hypothetical reconstruction of the skull of Telmatherium altidens 



One-sixth natural size. Designed to show especially the long postcanine diastema, 

 generic resemblance to T. ultimum. The lower jaw is Am. Mus. 2025 (type of T. 

 Am. Mus. 2060 (type of T. ultimum). 



piercing among all the known titanotheres, not except- ' 

 ing the giant Menodus giganteus of the Ohgocene. 

 Faint anterior and posterior ridges can be detected 

 on the anterior and posterior faces of the crown, 

 distinguishing this tooth readily from the canine of 

 Palaeosrjops major, in which the posterior ridge is on 

 the internal face of the crown. The very wide total 

 diastema between the canine and p2 measures 70 milli- 

 meters, as compared with 40 in Protitanotherium 

 superium and 45 in Telmatherium ultimum, which is 

 approached only by the wide diastema (51 mm.) in 

 Dolichorhinus hyognathus. The grinding series as a 

 whole measures 313 millimeters, as compared with 304 

 in P. emarginatum and 318 in P. superium, the lower 

 grinding series being, therefore, slightly smaller than 

 in P. superhum. 



Premolars. — Pi and p2 are not so much compressed as 

 in Telmatherium cultridens but are somewhat swollen 

 transversely. Pi (ap. 19 mm., tr. 12) is a simple, 



gently compressed cone, with a small posterobasal 

 cusp rising from the posterior ridge. This cusp is less 

 advanced than in Protitanotherium superhum or P. 

 emarginatum. P2 (ap. 27 mm., tr. 15) is also less 

 advanced than in those species, its posterior lobe being 

 smaller, lower, and much less crescentic superiorly. It 

 has a faint paraconid, no metaconid, and very faint 

 anterior and posterior internal valleys. It is thus 

 much like P2 of Manteoceras manteoceras, T. cultridens, 

 and (so far as known) T. ultimum. 



In striking contrast with this is the progressive 

 structure of pa (ap. 30 mm., tr. 18), especially its ex- 

 tremely prominent median cusp ( = protoconid); the 

 anterior and posterior crescents are correspondingly 

 more defined than in p^; the rudiments of the metastylid 

 and cusps appear, corresponding to the paraconid and 



..-;: . entoconid in the molars. P4 



is a decidedly larger tooth 

 (ap. 35 mm., tr. 23) with 

 prominent internal cusps ( = 

 paraconid, metaconid, meta- 

 stylid, entoconid). 



Molars. — The true molars 

 measure 195 millimeters in 

 length, as compared with 

 214 in Protitanotherium su- 

 perhum. The measurements 

 (ap. by tr.) are, nij, 45 by 29 

 millimeters; m2, 59 by 32; 

 ma, 89 by 35. The very 

 large size of the molars as in 

 P. superhum and other Uinta 

 C titanotheres is thus note- 

 worthy. The much worn 

 grinders give an imperfect 

 picture of the distinctive 

 characters of these teeth, but 



the elongated face, and the supposed 



altidens). The skull is restored from it would appear that the exter- 

 nal cingulum and the meta- 

 stylid are faintly indicated and that in ma the hypoconu- 

 lid is placed more on the internal or lingual side of the 

 crown, as in Palaeosyops paludosus. The grinding 

 series, therefore, presents two resemblances to that 

 of P. paludosus — namely, the prominent internal cusp 

 on Pa and the more internal position of the hypoconulid 

 on ma — yet neither of these characters is believed to 

 indicate genetic affinity. The closest resemblances are 

 to the inferior dentition of T. ultimum, from which 

 this jaw differs, however, in its greater size, its rela- 

 tively larger canines, and the more internal position 

 of the hypoconulid. This last condition may be partly 

 due to crushing. 



Jaw. — The jaw of T. altidens is readily distin- 

 guished from the jaw of Protitanotherium emarginatum 

 and that of P. superhum by its dolichopic characters, 

 the wide diastema between the canine (55 mm., esti- 

 mated) and Pi, and that between ma (54 mm.) and the 

 anterior border of the coronoid process. The sym- 



