372 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, , AND NEBRASKA 



length pi"* as 76 per cent of that of m'~^ but in M. 

 washaJciensis p^"* is only 71 per cent; in other words, 

 the molar series is relatively longer, which might be 

 expected, as there is a steady general increase in 

 the relative length of the molar series as we pass 

 from the lower Eocene Eotitanops to the Oligocene 

 Brontofherium. 



Jaws of Manteoceras washakiensis? from Washakie 

 A and B. — In the jaw from the base of Washakie A 

 (Am. Mus. 13176) doubtfully referred to M. wasTia- 

 Iciensis the dental measurements are all larger than 

 in the well-preserved jaw of M. manteoceras forming 

 Am. Mus. 1566 (p2-m3 182 mm. as compared with 168), 

 and the premolars are distinctly more progressive. 

 The large jaw from the Bridger (? level D) (Am. 

 Mus. 1563) referred to M. manteoceras agrees nearly in 

 size with Am. Mus. 13176. 



It is noteworthy that in all the explorations of the 

 Washakie B and Uinta B levels few or no remains refer- 

 able to Manteoceras have been found. The single 

 exception, and this of doubtful character, is the jaw 

 employed by Cope as the first cotype of his species 

 " Palaeosyops" vallidens. This specimen (Am. Mus. 

 5098), consisting of the two incomplete rami, from 

 Mammoth Buttes, Bitter Creek, regarded as an 

 upper Washakie level, apparently represents the 

 Washakie B stage of Manteoceras. (1) The measure- 

 ment of p2-ni3 (187 mm.) agrees almost precisely with 

 that of a M. manteoceras jaw (Am. Mus. 2353) as- 

 sociated with a skuU; (2) the measurements of ms 

 (ap. 57 mm., tr. 23) indicate a slightly longer tooth 

 than that in Am. Mus. 2353 (54 by 23). The char- 

 acters of the teeth and jaws are otherwise the same. 



Manteoceras uintensis Douglass 

 Plate LXIII; text figures 131, 132, 310, 312, 313 



[For original description and type references see p. 186] 



Type locality and geologic Jiorizon. — About 5 miles 

 northeast of well 2, Uinta Basin, Utah; gray sandstone 

 in lower part of Uinta formation {Diplacodon-Pro- 

 titanotJierium-Epihippus zone, Uinta C). The per- 

 sistence of Manteoceras in Uinta C is surprising because 

 that level also furnishes the next higher stage in the 

 phylum, namely, Protitanotherium. This persistence 

 is partly explainable by the fact that M. uintensis is 

 apparently an aberrant side branch with a decided 

 elongation of the muzzle and to some extent of the 

 tooth rows, or grinding series; in other words, it gives 

 certain indications of dolichopy, whereas the main 

 line {Protitanotherium) is mesaticephalic. 



Specific characters.- — SkuU larger than in M. manteo- 

 ceras (basilar length not known) ; muzzle relatively long, 

 horn swelling (?) not larger than in M. manteoceras; 

 zygomata not stout, in inferior view forming a marked 

 angle in front of the glenoid surface. Postcanine dia- 

 stema long (28 mm.), postcanine constriction very 

 marked; superiority in size of i' over i^ appearing less 



marked than in M. manteoceras; p'-m^ 240 millimeters; 

 p^ with deuterocone and tritocone more advanced than 

 in M. manteoceras; p* (ap. by tr.) 27 by 34; m\ 37 by 

 38; m', 49 by 52. 



That this species should be referred to the genus 

 Manteoceras is indicated by the round-topped incisors, 

 the robust, recurved canines, the twin convexities of 

 the premolar ectolophs, the broad, subhypsodont m', 

 with large parastyles and mesostyles, and the widely 

 arched zygomata. From the Bridger and Washakie 

 Basin species of Manteoceras the present one is dis- 

 tinguished by its larger size, more dolichocephalic 

 appearance, shorter free nasals, slightly more progres- 

 sive premolars, and more pronounced postcanine con- 

 striction. All these characters serve also to dis- 

 tinguish M. uintensis from Sthenodectes incisivus 

 (Douglass), which has very large, "cupped" incisors, 

 long, lanceolate canines, and very advanced premolars. 

 Affinities with Protitanotherium emarginatum and P. 

 superbum are indicated by the general form of the 

 incisors and canines, short nasals, and broad molars; 

 but weU-marked differences from these forms are seen 

 in the more elongate face, the larger size of the 

 incisors, more pronounced postcanine constriction, 

 and absence or arrested condition of the horn swelling. 



A remote analogy to Dolichorhinus is seen in the 

 lengthening of the face, of the postcanine diastema, and 

 of m^, as well as in the broad arching of the incisor 

 series. These dolichocephalic features in a mesati- 

 cephalic skull illustrate the subfamily kinship of 

 Manteoceras with Dolichorhinus. 



The skull as a whole must have been large, for the 

 distance from the premaxillaries to the glenoid region 

 of the squamosal is given as 430 millimeters, as com- 

 pared with 335 for the same measurement in M. 

 manteoceras, an increase of nearly 25 per cent. The 

 premaxillaries in correlation with the large size of the 

 incisors are angulate superiorly; the free nasals are 

 short (85 mm.), a progressive feature; the face is 

 long (255 mm., as compared with an average of 184 

 in M. manteoceras). The horn swellings were certainly 

 not larger than in M. manteoceras — a surprising fact, 

 because the large canines and incisors indicate male 

 sex. The infraorbital canal is broad; the zygoma is 

 deep in its middle portion, but apparently the buccal 

 swelling was slight or absent. Just back of the orbit 

 the malar was slender but not so slender as in 

 M. manteoceras; in inferior view the infraorbital 

 portion of the malar formed a low ridge which was 

 somewhat more pronounced than in M. inanteoceras 

 but did not form a distinct shoulder as it does in 

 Mesatirhinus and Dolichorhinus. The posterior nares 

 open opposite the metacone of m^, whereas in M. 

 manteoceras they sometimes open opposite the para- 

 cone of m'. 



Passing to the dentition, we note that the incisors 

 are intermediate in form between those of Manteoceras 

 manteoceras and of Protitanotherium emarginatum, 



