36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



CONDYLARTHRA 



HYOPSODONTIDAE 



PROMIOCLAENDS PIPIRINGOSI/^ new species 



Plate II, figures i, 2 



Type. — Right ramus of mandible with Mi and M2, U.S.N.M. 

 No. 20571. 



Horizon and locality. — Bison basin Tiffanian, saddle locality at 

 south rim of Bison basin, sec. 28, T. 27 N., R. 95 W., Fremont County, 

 Wyo. 



Specific characters. — Close in size of molar teeth to Promioclaenus 

 lemuroides (Matthew), but lower premolars noticeably smaller. Pre- 

 molars simple and but slightly inflated. P2 and P3 without parastylid 

 and without talonid cusps or crest. P4 with only a vestige of a para- 

 stylid, no metaconid, but exhibiting two small cusps at posterior mar- 

 gin of a very short talonid. Molars relatively narrow transversely 

 without entoconid, and hypoconulid on talonid rim of Mi and M2 well 

 defined. 



Discussion. — In addition to the type, a fragmentary jaw with P2-P4 

 (U.S.N.M. No. 21021) and a maxilla with M-M^ (U.S.N.M. 

 No. 21022) are believed to represent Promioclaenus pipiringosi. The 

 lower molars exhibited in the type are only slightly shorter anteropos- 

 teriorly than in the Torrejon Promioclaenus lemuroides material at 

 hand, but distinctly narrower relatively. Though worn, the cusps on 

 the marginal crest of the talonid appear comparatively well defined, 

 rather more as in teeth of the distinctly smaller Promioclaenus aqui- 

 loniiis of the Montana Fort Union. The lower premolars, if No. 21 021 

 is correctly referred, are small and not so inflated as in P. lemuroides, 

 though less slender than in P. aquilonius. Moreover, the anterior pre- 

 molars are without parastylid or any talonid cusps. P4, however, 

 shows a slight parastylid and a pair of cusps on the talonid ; neverthe- 

 less, there is no evidence of a metaconid so generally observed on this 

 tooth in P. aquilonius. The two upper molars in the tentatively re- 

 ferred maxillary fragment are much worn and exhibit few characters 

 of significance. The individual represented is a little smaller than the 

 type. The external cingulum is prominent between the paracone and 

 metacone and divided about midway. 



Use of the generic designation Promioclaenus Trouessart, rather 

 than Ellipsodon, for these forms, is in conformity with Dr. R. W. 

 Wilson's findings (1952) with respect to the genotype Ellipsodon 

 inaequidens. Trouessart proposed Promioclaenus for the two species 



12 Named for George N. Pipiringos, of the U. S. Geological Survey. 



