930 



EOCENE AND OLTGOCENE TITANOTHERES OF MONGOLIA 



depth being carried forward into the s,ymphyseal 

 region, a characteristic of Menodus (= Titanotherium) ; 

 the angular border is depressed, the coronoid is 

 elevated, broadly recurved; the simple, smooth, gently 

 rounded aspects of this jaw enable us to distinguish 

 it readily from the sharply angulate, sculptured, 

 relatively shallow jaw of the Dolichorhinus Icaiseni 

 type from the same formation, or from the extremely 

 elongate and deepened jaw of the Telmatherium 

 herkeyi type from the Irdin Manha formation. 



Protitanotherium andrewsl Osborn, 1925 



Original reference. — Osborn, H. F., Upper Eocene 

 and lower Oligocene titanotheres of Mongolia: Am. 

 Mus. Novitates No. 202, 1925. 



Am. Mus. 20254, male skull, superior dentition; Am. 

 Mus. 20262, jaws, symphysis, upper incisors and 

 grinders; Am. Mus. 20269, symphysis of jaws, with 

 canines; Am. Mus. 20280, juvenile palate, deciduous 

 premolars, first and second molars; Am. Mus. 20272, 

 fine jaw, male, inferior deirtition. These altogether 

 afford a very complete knowledge of the cranial char- 

 acters of this species. 



Specific cTiaracters. — This highly progressive phase 

 of Protitanotherium evolution is readily distinguished 

 from the previous ascending mutation of Protitano- 

 therium mongoliense by teeth apparently belonging to 

 higher geologic levels of the Shara Murun formation. 

 This advance is indicated not only by the greater 

 measurements of the cranium and jaws throughout, 



Figure 786. — Lower jaw of Protitanotherium andrewsi, Am. Mus. 20272 (A), a finely 

 preserved specimen, for comparison with the imperfect lower jaw of the type of 

 Protitanotherium mongoliense, Am. Mus. 18653 (B) 



A, one-sixth natural size; B, one-third natural size. Observe the very prominent external cingula on the premolars 

 and molars, especially on ma, as described in the text; the symphysis is somewhat deformed by downward 

 crushing: the male canines are of very large size. 



Type locality and geologic level. — The seven speci- 

 mens composing the type, paratype, and referred 

 skulls and jaws of this species are from the same 

 geologic locality and level as that which contains the 

 correspondingly abundant remains of Protitanotherium 

 mongoliense, yet they exhibit decidedly progressive 

 ascending mutations and rectigradations warranting a 

 specific separation. 



Materials. — The type (Am. Mus. 20271), a complete 

 male skull and dentition, nasals wanting; the paratype 

 (Am. Mus. 20251), a supposed male skidl, left ramus, 

 and inferior grinders; and five referred specimens — 



but by several progressive characters more or less 

 clearly observed in the grinding teeth, although the 

 grinders do not greatly exceed in length those of 

 Protitanotherium grangeri. 



Dentition. — The dental distinctions are as follows: 

 (1) Tetartocone shelf or spur prominent in p^~^, a 

 distinct tetartocone rudiment (Am. Mus. 20254) or 

 prominent tetartocone spur (Am. Mus. 20271) ob- 

 served in p^; (2) similarly faint rudiments of a hypo- 

 cone in m^ (Am. Mus. 20271), and a very distinct 

 conical hypocone (Am. Mus. 20254); (3) otherwise 

 the superior grinders, p'-m', exhibit similar characters 



