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A STUDY OF THE EARLY TERTIARY 



CONDYLARTHRAN MAMMAL 



MENISCOTHERIUM x 



By C. LEWIS GAZIN 



Curator, Division of Vertebrate Paleontology 

 U. S. National Museum 

 Smithsonian Institution 



(With 11 Plates) 



INTRODUCTION 



The genus Meniscotherium, although first described nearly ninety 

 years ago, has heretofore received but little systematic or detailed 

 study. Exception, however, must be made of E. D. Cope's rather 

 thorough treatment of the very limited material available to him by 

 1884. There are, nevertheless, rather numerous references to Menis- 

 cotherium in the literature of vertebrate paleontology, and these serve 

 not only to illustrate the wide interest that was early aroused, but 

 also to direct attention to the strikingly diverse opinions held as to 

 its relationships. 



Meniscotherium is a condylarthran mammal characterized by 

 primitive flat-nailed unguiculate or subungulate feet with essentially 

 a serial arrangement of the carpals and tarsals, but associated with 

 precociously selenodont teeth. Nearly all the known material is 

 early Eocene or Wasatchian in age, although one, or possible two, 

 Paleocene occurrences have been recorded. Its geographic distribu- 

 tion in Wasatchian time is the San Juan Basin of northwestern New 

 Mexico, the Green River Basin and adjacent areas of southwestern 

 Wyoming, and the valley of the Colorado River in western Colorado. 



Investigation of the morphology and relationships of this highly 

 interesting form was inspired by the abundant, unusually well-pre- 

 served remains encountered by Smithsonian Institution field parties 



1 Study of early Tertiary mammals is currently aided by a grant from the 

 National Science Foundation. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 149, NO. 2 



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