470 



TITANOTHERES Or ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



coossified nasals and "horns" ; see p. 208) of a titanothere 

 that now appears to be congeneric with the skulls 

 subsequently named by Cope Symiorodon iucco. The 

 present author formerly used the name Megacerops for 

 the generic group called Brontops by Marsh, but a re- 

 examination of Leidy's above-mentioned type of 

 Megacerops coloradensis has convinced him that this 

 was an error. In the present monograph the name 

 Megacerops includes the forms called by Cope "Sym- 

 horodon bucco" and "S. altirostris." (See pp. 212, 215.) 

 Brontotherium. — Marsh's Brontoiherium gigas, the 

 genotype of Brontotherium, rested upon a certain lower 



Brontops, Allops, Diploclonus, and Teleodus are all 

 now treated as distinct genera, although they were 

 formerly regarded by the author as referable to 

 Megacerops. 



SECTION 5. THE MENODONTINE GROUP 



SUBFAMILY BEONTOPINAE, INCLUDING THE PHYLA MAN- 

 TEOCERAS, PEOTITANOTHERIUM, TELEODUS, BRONTOPS, 

 AND DIPLOCLONUS 



STRATIGRAPHIC LEVEL AND DISTINGUISHING FEATURES 



The menodontine group consists of titanotheres of 

 upper Eocene to lower Oligocene age that reached a 



Figure 401. — Skulls of Rhadinorhinus and Brontotherium 



Palatal view. A, Rhadinorhinus iiploconus, Am. Mus. 1863 (type); White River, Uinta Basin, Utah, Uinta B 1; two-ninths natural 

 size. B, Brontotherium leidyi, Carnegie Mus. 93 (paratype); Chadron formation; one-sixth nattttal size. 



jaw in the Yale Museum (see p. 210), which the present 

 author regards as congeneric with the flat-horned skulls 

 that were later named by Marsh Titanops elatus, 

 Titanops medius, Titanops curtus. Marsh, however, 

 erroneously referred his type skull of "Brontotherium" 

 ingens to the genus Brontotherium. "B. ingens" 

 proves rather to be a synonym of Pomel's Menodus 

 giganteus. 



Symhorodon Cope is unfortunately a synonym of 

 Menodus Pomel, for the reason that the type species 

 Symiorodon torvus (see p. 211) was founded upon 

 lower jaws that appear to be congeneric with the type 

 jaw of Menodus giganteus Pomel. 



climax in the upper levels of the upper Titanotherium 

 zone. Related to the Eocene Manteoceras. Dis- 

 tinguished by progressively broad heads (brachy- 

 cephaly), short-crowned teeth (brachyodonty), and 

 short or moderately proportioned feet (mesatipody) . 

 Horns short, progressively shifting forward, of 

 primitive trihedral section at the base, rounded to 

 oval at the summits, progressively transverse oval. 

 Nasals progressively reduced in length and broadening 

 at the extremities. Incisor teeth with rounded 

 crowns; one or two pairs persistent above and below. 

 Canine teeth pointed, of medium length, progressively 

 obtuse. Premolar evolution retarded. Zygomata, 



