362 



TITANOTHERES OP ANCIENT "WYOMING, DAKOTA, AND NEBRASKA 



and Menodus nasals; (5) premaxillary symphysis 

 deepened and keeled (compare Oligocene genera); (6) 

 middle or frontal portion of the cranium flattened, the 

 flattening being associated with the progressive ob- 

 literation of the suture between the frontals and with 

 the abbreviation of the sagittal crest (compare Oligo- 

 cene genera); (7) middle portion of the skull saddle- 

 shaped in the region between the frontal-nasal horns 

 and occipital crest, showing a tendency that becomes 

 extreme in the Oligocene forms; (8) overhanging 

 supratemporal crests or ridges characteristic of age, 

 a tendency observed also in Oligocene titanotheres; (9) 

 occiput broadened and lateral pillars above the con- 

 dyles incipient, a feature observed in all Oligocene 

 titanotheres; (10) incipient expansion of the zygo- 

 matic portion of the squamosals and flattening out of 

 the squamosal portion of the zygoma, as in later 

 titanotheres; (11) deep backward angulation and 

 depression of the angle of the jaw, a feature observed 

 in certain Oligocene genera; (12) incisors tending to 

 become round-topped {M. uintensis), a tendency that 

 becomes very pronounced in the Oligocene genera; 

 (13) crowns of the canine teeth abbreviated, with 

 stumpy recurvature, foreshadowing the Oligocene 

 Brontops and Brontotherium; (14) ectolophs of the 

 premolar and molar grinding teeth elongated vertically, 

 a character that becomes pronounced in all Oligocene 

 titanotheres; (15) premolar ectolophs, showing incip- 

 ient double convexities, a character that becomes well 

 marked in all Oligocene genera; (16) fourth premolar 

 showing a famt suggestion of the tetartocones {M. 

 wasliakiensis) ; (17) premolars retarded in development. 

 Despite the approaches of Manteoceras to the Oligo- 

 cene Brontops in these 17 characters, there are reasons 

 why none of the known species of Manteoceras, and 

 especially the best known, M. manteoceras, can be 

 considered the direct ancestor of any known Oligo- 

 cene titanothere. This species differs from the Oli- 

 gocene titanotheres notably in the sharp postcanine 

 constriction of the face, the shallowness of the malar 

 below the orbit, and the slenderness of the malar 

 behind the orbit; and it is not yet known whether these 

 are progressive tendencies leading away from the 

 Oligocene type or are characters that were lost during 

 the transformation into the early Oligocene types, such 

 as Brontops iracTiycepJialus. 



Manteoceras Hatcher 



Plates XVI, XVII, XXIX, XLVI, LI, LIII, LV, LXIII, LXVII; 

 text figures 27, 29, 33, 87, 113, 121, 131, 132, 210, 215, 219, 

 220, 255, 302-313, 323, 324, 380, 406, 408, 409, 483, 484, 508, 

 510, 512-517, 521, 551-557, 566, 641, 646-649, 661, 673, 674, 

 685, 686, 688, 690, 701, 709, 710, 712, 717, 720, 721, 723, 724, 

 733, 745 



[For original description and type references see p. 177. For slceletai characters 

 see p. 630] 



Localities and geologic horizons. — Bridger Basin, 

 Wyo., levels C and, chiefly, D; Washakie Basin, Wyo., 

 level A; Uinta Basin, Utah, lower part of level C 

 {M. uintensis). 



Generic characters. — Facial concavities pronounced; 

 horn rudiments borne chiefly on the frontals; suborbital 

 portion of malars flattened, with a rudimentary shelf. 

 Superior incisors moderately enlarged; canines robust, 

 pointed, progressively more obtuse. Grinding series 

 subhypsodont; molar conules vestigial or wanting; 

 molars broader than in DolicliorJiinus or its allies; 

 premolar evolution retarded as to tritocones, deutero- 

 cones, and cingula; ectolophs with two convexities in 

 tandem. 



As described in detail m the revision of the nomen- 

 clature (pp. 177-178) the synonymy of the genus and 

 type species has been confused and complicated, but it 

 has now been definitely cleared up according to modern 

 principles. The honor of discovering this important 

 evolution stage of M. manteoceras and of first re- 

 cognizing its prophetic character belongs to Wortman, 

 who also invented the apt name Manteoceras (prophet 

 horn). Osborn in 1895, the first to publish a descrip- 

 tion of the skull of this animal, refrained from giving 

 it a new name on account of the general resemblance 

 in the teeth to the very imperfect type of Cope's 

 "Palaeosyops vallidens." Hatcher, later in the same 

 year, proposed the generic name and correctly de- 

 fined the genus. Still later Osborn in manuscript 

 referred to this form as Palaeosyops manteoceras; but 

 this specific name is technically to be credited to Hay, 

 who (1902.1) first fastened the specific name man- 

 teoceras to the previous description and figures of the 

 original "prophet horn" skulls, so that the name now 

 stands as Manteoceras manteoceras Hay (Osborn MS.). 



It is very important to note that seven skulls and 

 uppfr dentitions from the upper deposits of the 

 Bridger Basin (mostly level D) equal or exceed in 

 measurement and progressive characters three skuUs 

 from level A of the Washakie Basin and thus afford 

 corroborative evidence of the simultaneous deposition 

 of those sediments. 



Materials. — A somewhat detailed enumeration of 

 materials seems to be important in this case for 

 purposes of geologic correlation. 



1. Manteoceras manteoceras 



Bridger C 2: A fragmentary adult skull (Am. Mus. 12194), 

 from Burnt Fork post office (Henrys Fork). The sagittal crest 

 bifid with deep intermediate pit. This is in an early stage of 

 development. 



Bridger D: A male skull (Am. Mus. 12683), from Sage Creek 

 Spring, is important as supplementing the characters of the 

 type. It probably belongs to a somewhat early stage and 

 presents certain resemblances to the type of Telmatherium 

 cultridens. The measurement of p'-m^ is 176 millimeters, as 

 compared with 181 in the type of M. manteoceras. The most 

 striking feature (see figs. 305, 307) is the depth of the preorbital 

 concavities, which throws the frontonasal horn ridges into 

 exceptional prominence. The horn surfaces are slightly pitted 

 or rugose. 



Bridger C or D: A fuUy adult skull (Am. Mus. 1511) found 

 on Henrys Fork. Basilar length, 447 millimeters; p>-m', 184; 

 canines large. Probably a male specimen. 



