HISTORY OF THE JCONDYLARTHRA 



459 



much more likely that these problematical little tmeniscotheres 

 were merely a short-lived branch of the fCondylarthra. 



The fcondylarths were quite abundantly represented in 

 the Paleocene, where the genus \Euprotogonia was the fore- 

 runner of the Wasatch ^Phenacodus, but had an even more 

 primitive type of dentition. The upper molars were not 

 quadritubercular, but tritubercular, the three cusps arranged 

 in a triangle, the two outer ones forming the base and the single 





Fig. 234. — Lower Eocene '\coi\dy\iXYth, ]Memf>cothcrium terrce-ruhrw. Restored from 

 a skeleton in the American Museum. 



inner one the apex. This type of upper molar was, or is still, 

 common to the primitive and unspecialized members of a great 

 many mammalian orders, marsupials, insectivores, rodents, 

 carnivores, lemurs, artiodactyls, etc., and there is strong reason 

 to believe that the tritubercular molar was the common start- 

 ing point for almost all types of mammalian dentition. How- 

 ever that ma}^ be, ^Euprotogonia is of great interest as materi- 

 ally helping to close the gap between the clawed and the 

 hoofed mammals, belonging, as it did, to the latter and yet 



