396 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Dolichorhinus Hatcher 



Plates XVII, XXIX-XXXII, XLVI, LII, LIII, LV, LXXI- 

 LXXVII; text figures 27, 33, 105, 110, 125, 133-137, 140 

 210, 214-220, 254, 255, 302, 322-324, 335-337, 339-353, 483' 

 508-511, 520, 521, 579-585, 588-591, 647, 661, 685-686, 71l| 

 724, 733, 737-740, 742, 743, 745 



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

 p. 645] 



Generic cTiaraders . — Animals of relatively large 

 size, extremely dolichocephalic; cephalic indices 43 to 

 47; face relatively long; faciocephalic index 48 to 51; 

 postorbital process situated above m'; summit of 

 cranium broadly flattened; space above small brain 

 chamber filled with large air sinuses; occiput low and 

 broad; relatively prominent supraorbital horn swell- 

 ings on nasals; axis of face and middle part of skull 

 bent downward. Astragalus of the long-necked type. 



Figure 333. — Imperfect cranium of Mesaiirhinus petersoni 

 One-fourth natural size. Princeton Mus. 10041, Washakie Basin, Wyo., Washakie, i 

 view; As, occipital view; As, top view; A4, basal view. 



DolichorTiinus, appropriately named by Hatcher in 

 reference to the elongation of the nasal region, is a 

 titanothere in which we observe the dolichocephalic 

 extreme. The genotype species, D. Mjognathus , from 

 Uinta B 2, is connected by -transition forms in Uinta 

 B 1, such as Dolichorliinus longiceps and especially D. 

 superior, with the advanced structural stages of Mesa- 

 iirhinus, namely, M. petersoni, so that there is no 

 question that DolicliorMnus is a descendant of certain 

 species of Mesatirhinus. Besides the highly progres- 

 sive D. hyognathus and the more primitive D. longiceps 

 there are several species of Dolichorhinus less clearly 

 defined, a fact which indicates that this was a domi- 

 nant and highly diversified form during the period of 



deposition of the river sandstones and flood-plain 

 deposits of the levels Washakie B and Uinta B 1 and 

 B 2 (see below). 



History of discovery. — This animal first became 

 known through Cope's personal exploration of the 

 Washakie Basin exposures of 1872, which yielded his 

 cotypes of "Palaeosyops vallidens" ; this species ap- 

 parently represents a distinct stage of Dolichorhinus, 

 but unfortunately it is still known only from an im- 

 perfect lower jaw and some upper teeth. The next 

 discovery was that of Scott, Osborn, and Speir, of the 

 Princeton expedition of 1878, consisting of the large 

 lower jaw which in 1889 Scott and Osborn made the 

 type of the species "Palaeosyops hyognathus." The 

 third step was marked by Peterson's discovery in 1894 

 on behalf of the American Museum of Natural History 

 of several skulls and parts of skeletons 

 in the Uinta Basin. These skulls aroused 

 unusual interest because of the presence of 

 well-developed horn bases above the eyes, 

 in reference to which Osborn named the 

 animals Telmatotherium "cornutum." He 

 first considered that they represented a 

 direct progressive transition from "Tel- 

 matotherium vallidens" {= Manteoceras) 

 toward the Oligocene titanotheres, but, 

 as Hatcher pointed out in 1895, the horn 

 development in these animals is a paral- 

 lelism rather than a direct approach to 

 the Oligocene titanotheres, for accom- 

 panying these horns are other characters 

 which exclude the animals from such 

 ancestry. Hatcher accordingly separated 

 the species as a distinct genus, Doli- 

 chorhinus. It was long believed that 

 Dolichorhinus was confined to the Uinta 

 Basin level B 2, to which Osborn gave 

 the name Dolichorhinus cornutus zone. 

 The animal certainly occurs in Uinta B 2, 

 especially in the river-deposited sandstones, 

 A. Ai, Side jq very great abundance and may be con- 

 sidered as the dominant titanothere type 

 of this deposition because it so far outnumbers all 

 other types. 



The next step in discovery was made by the Ameri- 

 can Museum expedition of 1906 in the Washakie 

 Basin, during which Paul Miller found a beautifully 

 preserved skull and jaws of a Dolichorhinus associated 

 with parts of the skeleton and specifically identical 

 with the type of D. cornutus prevailing in Uinta B 2. 

 This discovery, together with evidence previously 

 found, demonstrated the synchronism of the Washakie 

 B 2 and the Uinta B 2 deposits. Further comparison 

 of the jaws of this Washakie specimen with the type 

 jaw of "Palaeosyops hyognathus," also from Washakie 

 B, demonstrated that the species D. cornutus is a syn- 

 onym of the earlier-described D. hyognathus. Exact 



