NO. 8 MAMMALIAN FAUNA, BADWATER AREA — GAZIN I3 



Horizon and locality. — Ilendiy Ranch member of Tepee Trail for- 

 mation on Dry Creek, S\L\ sec. 9, near line between sees. 9 and 16, 

 T. 39 N., R. 92 W., Wind River Basin, Wyo. 



Specific characters. — Teeth only slightly larger the& in Eomoropus 

 amarorum, but skull proportions and depth of lower jaw much greater. 

 Parastyle of upper molars increasingly prominent from M^ to M^, 

 considerably more extended anteroexternally than in Eomoropus an- 

 nectens, and evidently more so than in E. amarorum. 



Discussion. — One of the more important discoveries in the upper 

 Eocene of the Wind River Basin is the skull and jaw material of the 

 chalicothere, Eomoropus. The specimen (U.S.N.M. No. 21097) con- 

 sists of the left half of the skull and left ramus of mandible, and was 

 found by F. L, Pearce in exposures on an eastern tributary of the 

 east fork of Dry Creek about 20 miles west of the Badwater Creek 

 localities. The deposits here were mapped by Tourtelot ^ as the same 

 formation as that exposed along the south side of Badwater Creek 

 and are believed to be the same age. 



The species represented was earlier (Gazin, 1955, p. yy) thought 

 to be Eomoropus amarorum, but subsequent direct comparison with 

 the type, A.M. No. 5096, would seem to preclude this possibility. 

 E. amarorum was described by Cope (1881) from a specimen consist- 

 ing of the posterior portion of a skull, a lower jaw, and certain other 

 portions of the skeleton illustrated by Osborn (1913), and derived 

 from the Washakie Basin. According to Osborn, Cope's specimen 

 probably came from near the base of Washakie B, or the upper 

 Washakie. I suspect that the horizon represented is from higher in 

 the Washakie than suggested, inasmuch as E. amarorum would appear 

 to be more progressive than Uinta B Eomoropus annectens. 



Comparison of Eomoropus anarsius with the type of E. amarorum 

 shows similarities in the orbital region but the depth of the face below 

 the lower margin of the orbit is conspicuously greater, also the post- 

 orbital process of the frontal appears less prominent and overhanging. 

 The lateral view of the squamosal is similar in the two with the rela- 

 tive position of the external auditory meatus with respect to the 

 glenoid surface much the same. However, the distance between the 

 last molar and the glenoid surface is about 30 percent greater in 

 E. anarsius. Moreover, the depth of the lower jaw is also nearly 30 

 percent greater and the masseteric fossa n. e deeply impressed and 

 better defined. The two animals would appear to be at about the same 

 stage of maturity, with E. amarorum possibly a little older, to judge 



'' U.S.G.S. Oil and Gas Investigations Map OM 124, sheet i. 



