464 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Brontops dispar 



Diploclonus amplus 



Allops walcotti 



Figure 394. — Skulls of the menodontlne and brontotheriine groups 



Front view. One-twelfth natural size. 



Meuodontine group: A, Brontops dispar, horns short and thick, suhcurcular in section and pointed, nasals of moderate size, zygomata 

 moderately expanded, lateral incisors present, canines relatively long and conical. B, Brontops robustus, skull massive, horns comparatively 

 short and transversely expanded, with thick rugose tips, nasals short and robust, zygomata heavy, two large incisors, canines short, thick, 

 and conical. C, Diploclonus amplus, horns divergent, very wide at base and rapidly narrowing to the pointed tips, an accessory hornlet, 

 nasals small, zygomata expanded. D, Allops walcotti, skull small and slender, horns very small, nasals broad, zygomata deep and slender. 



E, Allops serotinus, long divergent horns narrowing but little toward the tip, zygomata of moderate size, canines slender and pointed. 



F, Menodus giganteus, long divergent horns narrowing rapidly to pointed tips and trihedral in section, nasals expanded distally, zygomata 

 relatively small and deep, canines (not shown) elongate pointed, incisive border edentulous. 



Brontotheriine group: O, Megacerops copei, J, horns long, erect, and cylindrical, with no connecting crest, nasals thin, zygomata not widely 

 expanded (diminished by crushing), canines small, rounded, and close together, premolars upturned anteriorly. H, Brontotherium gigas, 

 cf , skull very wide, zygomata enormous, horns long and wide, nasals of intermediate length, two incisors on each side, canines short and 

 swollen. I, Brontotherium curium, 9?> horns short but very broad and massive, with high connecting crest, nasals short and narrow, 

 zygomata not widely expanded, canines swollen. 



