SYSTEMATIC CLASSIFICATION OF THE TITANOTHERES 



249 



Group I. Short-horned — Continued. Pages 



9. Subfamily Brontopinae — Continued. 



Genus Brontops Marsh (with two or one 



lower incisors; lower Oligooene) . 222, 482, 664-676 



Species brachycephalus (Osborn) 231, 



483, 675, 676 



dispar Marsh 223, 488, 664 



robustus Marsh i___ 222, 492, 666 



fangustigenis (Cope) 219,482 



Genus Diploclonus Marsh (with internal 



branching horns; lower Oligocene) 227, 



499, 675-678 



Species ftyleri (Lull) 234, 502, 675 



fbicornutus (Osborn) 231,501 



amplus Marsh 227, 504 



selwynianus (Cope) 225,502 



10. Subfamily Menodontinae ( = ?Diplacodontinae) 

 Osborn. "Menodonts." (Lower Oligocene 

 and possibly upper Eocene titanotheres. Heads 

 of medium width, progressively elongating 

 (Menodus) or broadening (Allops); horns 

 short, trihedral in section; incisor teeth vesti- 

 gial; grinding teeth long-crowned with promi- 

 nent cingula; premolars with accelerated 

 tetartocones.) 

 Genus Menodus Pomel {— Titanolherium 



Leidy) 204, 522, 681 



Species heloceras (Cope) 212, 524, 681 



iorvus (Cope) 210,525 



proutii (Owen, Norwood, and 



Evans) 205,526 



trigonoceras {Cope) 213,528,683 



varians (Marsh) 223,535 



giganieus Pomel 204, 530, 687 



Genus Allops Marsh 224, 506, 678 



Species walcotli Osborn 241, 509 



marshi (Osborn) 233,511,678 



serotinus Marsh 225, 515 



crassicornis Marsh 228,517,679 



Group II. Long-horned: Pages 



11. Subfamily Megaceropinae ( = ?Rhadinorhininae) 



Osborn. "Megaceropines," "symborodonts." 

 (Relatively small, long-horned titanotheres, 

 possibly descended from Rhadinorhinus. Of 

 lower Oligocene age. Horns precociously 

 evolved, with little or no connecting crest; 

 head mesaticephalic to brachycephalic, oypto- 

 oephalic; narrow-lipped; premolars with pre- 

 cocious tetartocones; grinding teeth without 

 cingulum; vestigial incisor teeth.) 

 Genus Megacerops Leidy { = Symborodon 



Cope) (horns rounded, erect) 208,541,691 



Species riggsi Osborn 242, 550 



assiniboiensis Lambe 239, 549 



copei (Osborn) 235, 548 



acer Cope 211, 545 



bucco (Cope) 212, 544 



coloradensis Leidy 208, 544 



?syceras (Cope) 226, 549 



12. Subfamily Brontotheriinae ( = ?Diplacodontinae) 



Osborn. "Brontotheres." (Lower Oligocene 

 titanotheres. Primitively dolichocephalic, pro- 

 gressively mesaticephalic and brachycephalic, 

 slightly cyptocephalic; broad-lipped; very pre- 

 cocious development of the horns; accelerated 

 development of internal cones of superior pre- 

 molars; prominent cingulate incisor teeth in 

 males.) 

 Genus Broniotherium Marsh (horns progres- 

 sively elongate, nasals abbreviate; lower 



Oligocene) 209, 555, 690 



Species leidy i Osborn 234, 558, 690 



hypoceras (Cope) 216,562 



hatcheri Osborn 235, 563, 695 



tichoceras (Scott and Osborn). 219, 565 



gigas Marsh 209, 567 



dolichoceras (Scott and Osborn). 220, 572 



medium (Marsh) 228,576 



curtum (Marsh) 224, 574 



ramosum (Osborn) 231,577 



platyceras (Scott and Osborn). 221, 578 

 frumelicum (Toula) 230, 560 



Note. — Additional species are described and classified in the appendix, 

 including Mongolian, east European, and Burmese titanotheres. 

 -29— VOL 1 19 



