340 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



pensated for, as above noted, by the development of 

 the tusks. As a second conservative character it is 

 important to note that the first and the second lower 

 premolar teeth exhibit in T. culfridens a distinctively 

 high, laterally compressed, and secant character, and 

 that vestiges of this character are conserved in the 

 species T. altidens of Uinta C. The free or projecting 

 portion of the nasals remains relatively short (T. 

 ultimum) . 



All the other distinctive incipient dolichocephalic 

 characters of Telmatherium appear to be progressive: 

 (1) the lateral superior incisors are decidedly progres- 

 sive, becoming elongate and tusklike; (2) the hypso- 

 donty in the superior grinding teeth becomes more 

 marked; (3) the posterior superior premolars (p^"*) 

 acquire similar internal ridges longitudinally placed, 

 which in T. ultimum tend to develop tetartocones; 

 (4) there is a decided elongation of the postcanine 

 diastema, culminating in the very long diastema 

 of T. altidens; (5) there is a marked elongation of the 

 third inferior molar (ms); (6) while the canines of 

 T. ultimum are not relatively larger than those of 

 T. cultridens, the canines of T. altidens of Uinta C are 

 exceptionally large and show progressive development 

 of this character; (7) the ectolophs of the superior 

 premolars as seen in T. ultimum of Uinta C tend to 

 develop symmetrical convexities of protocones and 

 tritocones such as are characteristic of all Oligocene 

 titanotheres. 



Sex cliaraders. — Differences in sex are indicated 

 very markedly in the male and female specimens of 

 T. ultimum in the inferior size of the canines in the 

 female, and apparently also in the absence or faint 

 development of the horn rudiments. Contrary to an 

 earlier opinion of the author it now appears that even 

 in their first development the horn swellings are less 

 prominent and rugose in the female than in the male 

 Eocene titanotheres. 



Resemhlaiices to the Oligocene Menodus. — There are 

 many resemblances in Telmatherium ultimum to the 

 characters of the Oligocene genus Menodus, as follows: 

 (1) Middle region of the skull between the orbits and 

 the postglenoid processes lengthened; (2) molar series 

 enlarged absolutely and proportionally both in length 

 and in breadth; (3) canines of sublauceolate form; 

 (4) grinding teeth sharp and hypsodont; (5) post- 

 temporal and occipital regions similar in their rounded 

 and elevated form, also in the absence of the separate 

 condylar pillars at the back of the occiput and in the 

 presence of accessory articular facets above the fora- 

 men magnum; (6) zygoma deep in section in both 

 Telmatherium and Menodus, with a vertical flange; 

 (7) coronoid process high and slender. 



Contrast with Menodus. — On the other hand, Tel- 

 matherium appears to be excluded from the ancestry 

 of Menodus by the wholly different trend of develop- 

 ment of certain parts: (1) the elongation of the post- 



canine diastema seems to be a progressive feature 

 culminating in T. ultimum, whereas in Menodus this 

 diastema is much reduced; (2) the progressive increase 

 in size of the incisors contrasts with the extremely 

 vestigial condition of the incisors in Menodus; (3) all 

 the Uinta Basin species of Telmatherium and Dolicho- 

 rhinus are characterized by the great prominence of 

 the incisor series and by sharp constriction of the face 

 back of the enlarged canines, probably indicating 

 grazing habits, and no species seems to fulfill all the 

 ancestral conditions of any of the Oligocene titanotheres. 

 It therefore can not be said that we now know any 

 species of Telmatherium that would fill the ancestral 

 characters of the Oligocene Menodus. 



Telmatherium Marsh 



(Leurocephalus Osborn, Scott, and Speir) 

 Plates XVI, XLVI, LI, LV, LXIII-LXV; text figures 126, 

 127, 210, 219, 220, 223-226, 255, 256, 289-300, 508, 516, 

 588, 592, 593, 647, 717, 733, 735, 745 



Generic characters. — Skull as a whole long, basi- 

 cranial region short, zygomata spreading, with deep 

 malar flanges; frontonasal horn swellings rudimentary 

 or wanting. Incisors large, with heavy posterior 

 cingulum; i^ very large and pointed; canines large, 

 compressed, pointed, with sharp anterior and posterior 

 borders; upper premolars relatively advanced, with 

 complete internal cingulum; upper molars sub- 

 hypsodont, relatively large, with rudimentary conules 

 and slender parastyles and mesostyles, m^ without 

 hypocone. These animals are without difficulty dis- 

 tinguished from the species of Mesatirhinus and 

 Dolichorhinus, but the earlier stages show certain 

 resemblances to Manteoceras manteoceras. 



The known specific stages are as follows : 



T. cultridens, from Bridger ?C or D. The premolar- 

 molar series measures 180 millimeters. The premolars 

 are somewhat simpler in structure than in T. validum. 

 The animal is inferior in size to T. validum and is of 

 the same size as the smaller members of M. manteoceras. 



T. validum, Bridger D. The premolar-molar series 

 measures 195 millimeters. This animal is represented 

 by part of a male skull, the only specimen Icnown. 

 The lateral superior incisor is more distinctly canini- 

 form than in T. cultridens, and the premolars and 

 molars are somewhat more progressive. 



T. ultimum, from Uinta C. The premolar-molar 

 series measures 217 millimeters. The lateral superior 

 incisors are greatly enlarged and caniniform; the 

 superior premolars are progressive and have more 

 symmetrically convex protocones and tritocones and 

 well-defined external cingula. The second superior 

 premolar is simpler than the third and fourth. 



T. altidens, from Uinta C (? lower levels). The 

 inferior premolar-molar series measures 330 milli- 

 meters. The anterior premolars are primitive and 

 laterally compressed. The canines are exceptionally 

 prominent, hence the name T. altidens. 



