212 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Megaceratops heloceras Cope, 1873 



Cf. Menodus heloceras, this monograph, pages 524, 681 



Original reference. — Pal. Bull. No. 15, p. 4, "issued 

 August 20, 1873" (Cope, 1873.2). 



Subsequent reference. — Cope, Report on the verte- 

 brate paleontology of Colorado, pp. 487-488, 1874 

 (Cope, 1874.2). 



Type locality and geologic horizon. — Horsetail Creek, 

 northeastern Colorado; Chadron formation {Titano- 

 therium zone), level not ascertained. 



Type. — "A cranium * * * with nearly com- 

 plete maxillary dentition," anterior teeth and part of 

 frontals wanting. Am. Mus. 6360. (See fig. 168.) 



Specific characters. — Cope writes: 



There is a prominent horizontal superciliary ridge without 

 horns, and two short obtuse horn cores on the muzzle. These 



Figure 167. — Type (holotype) skuU of Megaceratops acer 



Am. Mus. 6348. After Cope, 1874. One-sixth natural size. 



diverge outward, the outer sides being flattened and the sum- 

 mits contracted and truncate. They are mere rudiments of 

 the horns seen in M. aceronsor [sic], M. coloradoensis. The 

 molar teeth do not exhibit the T-shaped cross ridges seen in 

 Miobasileus, and the two outer crescents are continuous with 

 each other. 



Measurements 



Millimeters 

 Length from posterior rim of temporal fossa to middle of 



osseous eyebrow 472 



Least width of parietal plane 104 



Superciliary width 260 



Elevation of horn core 50 



Etymology. — ^Xos, wart; xepas, horn; in allusion to 

 the wartlike appearance of the horn. 



Present determination. — The species 

 referable to the genus Menodus. (See p. 



Symborodon bucco Cope, 1873 

 Cf. Megacerops bucco, this monograph, page 544 

 Original reference. — Synopsis of new Vertebrata 

 from the Tertiary of Colorado, p. 11, 1873 (Cope, 

 1873.3). 



is valid 

 524.) 



but 



Subsequent reference. — Cope, Report on the verte- 

 brate paleontology of Colorado, pp. 484, 485, pis. 

 2-4. 1874 (Cope, 1874.2). 



Type locality and geologic horizon. — Horsetail Creek, 

 northeastern Colorado; Chadron formation {Titano- 

 therium zone), level not ascertained. 



Cotypes. — In the original description Cope says the 

 species is represented "by an imperfect cranium; by 

 a cranium almost perfect, including very probably 

 both mandibular rami, with entire dentition; a frag- 

 mentary skeleton, including parts of cranium, teeth, 

 and vertebrae; and by a series of cervical and dorsal 

 vertebrae." Which of these cotype individuals thus 

 mentioned shall we select as the lectotype? If we 

 should take the first specimen mentioned, namely, the 

 imperfect cranium (known to be Am. Mus. 6346), we 

 find that since it consists of only the posterior portion 

 it lacks most of the characters given in the specific 

 description, except the single one of possessing ex- 

 panded zygomata (hence the name hucco). On the 

 other hand the "cranium almost perfect" (Am. Mus. 

 6345) also has expanded zygomata and was evidently 

 the chief specimen, since it furnished most of the 

 specific characters and measurements given in the origi- 

 nal description; moreover, in Cope's 

 fuller report (1874.2) it was figured 

 in Plates 2, 3, 4, imder the name 

 Symhorodon hucco, and in the key to 

 the species (p. 484), in which S. hucco 

 is contrasted with S. altirostris, the 

 diagnostic characters (referring to 

 the horns, premolars, nasals, de- 

 pressed cranium) are evidently from 

 the "cranium almost perfect" (No. 

 6345) rather than from the "im- 

 perfect cranium." 



Lectotype. — From these clear indi- 

 cations of the author's intention the 

 skull (Am. Mus. 6345) may therefore be regarded 

 as the lectotype. (See figs. 169, 170.) 



Specific characters. — Cope mentions especially the 

 enormous buccal expansion of the zygomata, the char- 

 acters of the horns, nasals, skull top, orbits, etc. 

 Specific characters are fully given on page 544. 

 Etymology. — hucco, one having extended cheeks. 

 Present determination. — This species is provisionally 

 regarded as a valid one. 



Symborodon altirostris Cope, 1873 



Cf. Megacerops acer, this monograph, page 545 



Original reference. — Synopsis of new Vertebrata 

 from the Tertiary of Colorado, p. 12, 1873 (Cope, 

 1873.3). 



Subsequent references. — Cope, Report on the verte- 

 brate paleontology of Colorado, p. 486, pis. 5, 6, 8, 

 fig. 1, 1874 (Cope, 1874.2); The Perissodactyla, pi. 33, 

 fig. a, opposite p. 1062, 1887 (Cope, 1887.1). 



