928 



EOCENE AND OLIGOCENE TITANOTHEEES OF MONGOLIA 



(Am. Mus. 20110) the external sculpturing of the 

 premolars is marked; these teeth are somewhat more 

 hypsodont, and it is possible that we have to do with 

 another species of Protitanotherium in the Irdin Manha 

 horizon distinct from P. grangeri. Hence the specific 

 reference is entered thus in our table on page 915 : "Am. 

 Mus. 20110, Protitanotherium grangeri? , referred. 

 Large male jaws with complete dentition." 



together in a single quarry near the Kaisen quarry, as 

 shown in Figure 770. These very fine materials 

 include the type right ramus, a fragment with six 

 grinding teeth (Am. Mus. 18653); the neotype palate 

 and dentition complete (Am. Mus. 20263); also four 

 referred specimens — Am. Mus. 20256, palate, canine, 

 superior grinders, lower jaws; Am. Mus. 20261, female 

 skull complete but crushed, incisors, canine, grinders; 



Figure 784. — Protitanotherium mongolit 



e, Am. Mus. 20263 (neotype). Palate and complete superior dentition lacking 

 only the median incisor teeth 



Observe especially the rudimentary tetartocones in p'-', the still more rudimentary tetartocone in p*, the extremely rudimentary hypocone indicated in ms, 

 particularly in right m^, as compared with the corresponding rectigradations of the premolar and molar teeth in the less progressive Protitano- 

 therium grangeri and in the more progressive P. andrewsi. One-third natural size. 



Protitanotherium mongoliense Osborn, 1923 



Original reference. — Osborn, H. F., Titanotheres and 

 lophiodonts in Mongolia: Am. Mus. Novitates No. 91, 

 October 17, 1923, p. 3. 



Type locality and geologic level. — On the Kalgan- 

 Uliassutai traU, near Ula Usu, southeastern Gobi, 

 Mongolia; Shara Murun formation (uppermost 

 Eocene). 



Materials. — The materials of this species differ from 

 those referred to Protitanotherium grangeri ia their 

 occurrence, the specimens having been found close 



Am. Mus. 20270, right maxUla, zygoma, superior 

 grinders; Am. Mus. 20273, fine pair of jaws lacking 

 symphysis, inferior grinders. These materials agree in 

 their general stage of rectigradations and progression, 

 which is less advanced than that shown in the materials 

 found in the same vicinity and referred to Proti- 

 tanotherium andrewsi. 



Specific characters. — The skull, the two palates, the 

 right maxilla, and the two pairs of jaws agree suffi- 

 ciently with the type jaw in size and in progressive 

 evolution of the incisors, canines, and grindiag teeth 



