58 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



tus and the allied Tomitherium. At this time he still harbored the idea that the Lemuroidea, the Insec- 

 tivora, and the Condylarthra were closely related, but he does not mention the group Mesodonta as such; 

 he merely says "In the following pages I will not attempt to distinguish which of the genera are lemuroid 

 and which are insectivorous, since the ungual phalanges are yet unknown. An exception must be made 

 in the case of the genus Pelycodus, where a single compressed acute claw is known. This alone does not 

 decide the question, since such a claw exists on the second toe of many Lemuroidea" (pp. 458-459). 

 He referred Nothardus, Tomitherium, the European Adapts, and four other genera to the Adapidse, and 

 he speaks of the latter family as "the most primitive type, and the one most nearly allied to the Condyl- 

 arthra, from which they were probably derived" (p. 459). He left Pelycodus "of uncertain reference to 

 this family and order" (p. 460), on account of the supposed creodont character of the feet. 



While the number of described species and genera of Eocene primates increased apace, so that by 

 1902 there were fifty-nine nominal species, very little more had been done in the way of clearing up the 

 precise relationships of these early forms, owing to lack of well-preserved skulls and limbs. 



In 1887, however. Dr. Schlosser, in his monographic review of the Apes, Lemurs, Bats, Insectivores, 

 Marsupials, Creodonts and Carnivores of the European Tertiary, expressed a doubt as to the association 

 of the above-mentioned foot material with Pelycodus. "The bones are almost too large for Pelycodus,'^ 

 he says, "and I am almost persuaded to refer them to a Creodont" (p. 22, footnote 1). Accordingly, he 

 placed Pelycodus along with Hyopsodus and Microchoerus in the Hyopsodidse, while Nothardus with 

 Tomitherium were referred to the Adapidse, his conclusions being based veiy largely on the characters of 

 the teeth. He also pointed out the resemblance of Leidy's Omoviys to the European genus Necrolemur, 

 which had been described by Filhol in 1873. 



In 1892 Zittel referred all the above mentioned genera to a family " Pachylemuridse " Filhol, of the 

 suborder Prosimise (Lemuroidea), but the error in regard to the creodont characters of the feet of Pely- 

 codus was still followed and Pelycodus was place next to Hyopsodus and Microsyops. 



In 1899 Dr. W. D. Matthew in his "Provisional Classification of the Fresh Water Tertiary of the 

 West" traced the geological succession of the American Eocene primates and reduced Limnotherium 

 and Tomitherium to the rank of synonyms of Notharctus. 



In 1902 Professor Osborn, whose "Revision of the American Eocene Primates" is the basis for all 

 subsequent systematic work on this group, placed Pelycodus with Notharctus in the family Notharctidse. 

 This was partly a result of Dr. Matthew's observation, made independently from that of Schlosser, that 

 the feet referred by Cope to Pelycodus probably belonged to a creodont. It was also due to the close 

 similarity in dental structure between Pelycodus and Notharctus, which was revealed by Osborn's and 

 Matthew's comparisons of the successive species of Pelycodus in the Lower Eocene and of Notharctus 

 in the Middle Eocene. This was an important step toward clearing up the further relationships of these 

 forms. While recognizing the close relationships of Pelycodus and Nothardus, Osborn defined Pelycodus 

 as an earlier and more primitive stage with the upper molars more or less tritubercular and lacking the 

 mesostyle. He regarded the Notharctidse as a distinct family from the European Adapidse, distinguished 

 by characters of the dentition. He referred to the genus Notharctus Leidy the various species comprising 

 the genera Limnotherium and Thinolestes Marsh, Hipposyus Leidy, and Tomitherium Cope, and traced 

 the evolution of the dentition from Pelycodus frugivorus of the Lower Eocene to Telmatolestes crassus 

 of the Upper Bridger. 



Regarding the relationships of the Eocene Primates Professor Osborn said: 



It may be possible with the material now in hand to positively determine the relationships of some of these forms 

 to the existing Anthropoidea or Lemuroidea; but it will require detailed investigation, which I am not able to undertake 



