460 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Megacerops copei " 



Megacerops acer 



Figure 390. — Skulls of the brontotheriine group 



Side view. One-twelfth natural size. 



Subfamily Brontotheriinae: A, Srontotherium leidyi, a primitive member of the Brontotkerium phylum with short horns transversely oval in 

 section, long nasals tapering and decurved, canines short and swollen, two stout incisors, and cheek teeth with but little external cingulum; 

 Chadron A. B, Brontotkerium gigas, a progressive brontothere with long erect horns transversely oval in basal section, nasals of intermediate 

 length, zygomata widely expanded, occiput long, and a marked parietal convexity; Chadron C. G, Brontotherium curium, a highly advanced 

 brontothere with very long horns far in front of the orbits and much flattened anteroposteriorly, nasals short, skull top long, and zygomata 

 much expanded; Chadron C. D, Brontotherium (.peltoceras) curtum, a female brontothere with skull short and massive, horns very thick, high 

 connecting crest, and nasals short. 



Subfamily Megaceropinae: E, Megacerops copei, long horns thick at the base, nasals long and thin, canines very short and swollen, premolar 

 series upturned, and zygomata massive. F, Megacerops acer, horns of moderate length but very thick at the base, nasals short and thick, 

 premolar series upturned, zygomata heavy, midparietal swelling prominent. 



Compared with the Menodontinae, members of this group usually have the skull top less deeply concave, and many have a parietal swelling. 

 The horns are commonly transversely oval in section, the premolar series upturned anteriorly, and the canines in males short and swollen. 



