296 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



posterior border of the angle; (5) the elongate (70 

 mm., estimated) symphysis laterally compressed 

 l)ehind the canines; (6) the slope of the anterior border 

 of the coronoid directly into the fang of ms; (7) the 

 moderately thick rami (18 mm.). The lower profile 

 or contour of the jaw is convex below the molars, 

 concave below the coronoid, extending backward into 

 the angle. 



Inferior teeth oj E. princeps {type; PI. LIV). — There 

 were apparently three inferior incisors, the crowns of 

 which are not preserved. The alveoli of the inferior 

 canines are slightly compressed laterally; the esti- 

 mated measurements are 15 millimeters (antero- 

 posterior) by 13 (transverse). The crown of pi is 

 not preserved; its fang is single; the fang is separated 

 from that of the canine by a very narrow diastema 



Figure 253. — Lower grinding teeth of three species of Eotitanops from 

 the upper Huerfano formation (Huerfano B) 



Natural size. After Osborn, 1919. A, A', E. minimus (type), lower level of the upper 

 horizon of the Huerfano formation; B, Bi, E. gregoriji (referred specimen), from the 

 upper Huerfano; C, E. hrownianus (referred specimen), from near the base of the 

 lower Huerfano. 



(3 mm.); behind it is a continuation of the diastema, 

 16 millimeters in width. This diastema points to a 

 somewhat elongate character of skuU and jaw, since 

 the total length between the canine and p2 is 31 

 millimeters. P2, measuring 13 by 6 millimeters, is 

 an elongate, laterally compressed, bifanged tooth with 

 an elevated paraconid and depressed metastylid or 

 posterior cusp, noncingulate and with the faintest 

 indication of valleys on the inner surface. P3, meas- 

 uring 12 by 7 millimeters, is slightly more progressive, 

 with its metaconid externally placed and a more clearly 

 indicated posterior valley. P4, measuring 13 by 8 

 millimeters, exhibits a broader talonid and is thus 

 submolariform. The molars are perfectly pi'eserved. 



aggregating 65 millimeters in length, 14 in maximum 

 width of crown. The individual total measurements 

 (ap. by tr.) are as follows: Mj, 17 by 12 millimeters; 

 m2, 21 by 13; ma, 26 by 14. 



This progressive increase posteriorly accords with 

 a similar increase of the upper molars posteriorly, as 

 observed also in Larnhdotherium. The inferior molars 

 exhibit faint external and no internal cingula; rather 

 low but well-defined crescents; a progressive increase 

 in size; paraconids partly defined on ms. The most 

 distinctive primitive feature in ma is the small size, 

 subconic form, and mesial position of the hypoconulid 

 as compared with its backward extension and cres- 

 centic form in some of the middle Eocene types. 



Eotitanops major Osborn 



Text figures 145, 483, 506 



[For original description and type references see p. 193. For skeletal 

 characters see p. 697.] 



Type locality and geologic Tiorizon. — Alkali 

 Creek, Wind River Basin, Wyo.; Wind Eiver 

 formation, Lamidotherium- Eotitanops - Cory- 



;., phodon zone (Wind River B, "Lost Cabin"). 



7 -•iMNoi744i Specific characters. — The type and only known 

 specimen (Am. Mus. 14894) consists of a left me- 

 dian metatarsal associated with the distal end of a 

 tibia. It is distinguished from E. princeps by its 

 notably larger size (length of Mts III, 104 mm., 



' greatest width, 16). The skull and dentition are 



not known. 



Eotitanops minimus Osborn 



Text figures 155, 253 

 [For original description and type references see p. 199.] 



Type locality and geologic horizon. — Huerfano 

 Park, Colo.; Huerfano formation, Eometarhinus- 

 j_ Palaeosyops fontinalis zone (Huerfano B; lower 



1 level). 



Specific characters. — As this is the smallest true 

 titanothere known, Osborn (1919.494, p. 564) as- 

 signed to the type lower molar teeth P4-m3 (Am. 

 Mus. 17439) the specific name minimus. The 

 measurement of p4-m3 (53 mm.) is much less than 

 that (58 mm.) of the corresponding teeth in E. 

 gregoryi, yet the other characters are so similar to 

 those of E. gregoryi as to suggest that this is a related 

 form. Figure 253 exhibits the form and size of three 

 species, minimus, gregoryi, and hrownianus. A large 

 number of measurements of Eocene titanotheres show 

 that no single species exhibits so great a range in size. 

 The discovery of this dwarf titanothere, together 

 with the presence of titanotheres of the same size as 

 E. gregoryi and E. hrownianus in Huerfano B and 

 Wind River B, reveals the existence of what is probably 

 a distinct phylum of diminutive titanotheres separable 

 from the Eotitanopinae. We must, however, await 

 the discovery of the skeletons before this supposition 

 can be confirmed. 



