GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



59 



at present. [Footnote] : Dr. J. L. Wortman is now taking up these problems with tlie rieh materials afforded by the Yale 

 Museum Collections. I therefore omit phylogenetic questions here. 



Three suppositions are possible: First, that these Primates represent an ancient and generalized group (Mesodonta, 

 Cope) ancestral to both Lemuroidea and Anthropoidea; second, that they include representatives of both Lemuroidea 

 and Anthropoidea, contemporaneous and intermingled; third, that they belong exclusively to one or the other order. 

 There are certain advantages in the revival of the term Mesodonta Cope, a suborder (anticipating the terms Pseudole- 

 muroidea and Tarsii) which would bear somewhat the same relationship to the modern specialized Monkeys and Lemurs 

 that the Condylarthra bear to the Ungulata and the Creodonta to the Carnivora. The serious difH(ult>' with this view 

 is the very considerable separation of these families (op. cit., pp. 176-1 7S). 



Accordingly Osborn retained Cope's suborder Mesodonta, including the three families Hyopsodontida? 

 Schlosser, Notharctidse Osborn, and Anaptomorphidse Cope. The Hyopsodontidse have since been 

 removed by Wortman and by Matthew from the primates, and were referred at first to the Insectivora 

 and finally to the Condylarthra (Matthew, 1914); the Anaptomorphida have since been shown to be 

 allied to the existing Tardus. 



In the family Notharctidse Osborn traced the changes in the dentition, beginning with Pelycodus frugi- 

 vorus of the Lower Eocene and culminating in Telmatolestes crassus of the Upper Bridger. 



In 1904 Dr. Wortman, who had studied the Marsh collection at Yale University, denied the 

 vaUdity of the order Mesodonta: 



As regards the A alidity of the group Mesodonta of Cope and its suggested revival by Osborn, ^■ery little need be said. 

 From the most abundant skeletal materials of both Adapts and Noihardus we now know that the hallux was almost if 

 not quite as opposable as in any living Primate. Cope's statement, therefore, of its lack of opposability in Pelycodus, a 

 genus scarcely distinct from Nothardus, must with almost absolute certainty be erroneous. His technical definition of the 

 group, moreover, as well as its dissociation from the Primates, I regard as utterly unsound, illogical, and in no wise war- 

 ranted by the facts. I do not believe that any such natural group exists, and a revival of the name Mesodonta can result 

 only in confusion. As we have already seen, there are types of very different affinities among these ancient Primates, 

 and this fact in my judgment effectually precludes the possibility of their association into a single group (pp. 409-410). 



With reference to the relationship of Nothorctus and Adapis to modern types, Wortman argued as 

 follows : 



What position, then, ilo Adtipis and Nofluirdiis occupy with reference to these natural groups already outlined? That 

 they can not be consistently placed in the Lemuroidea is ex ident for the following reasons: The incisors do not exhibit 

 any traces of lemurine modification, but, on the contrary, are like those in typical monkeys; the main entocarotid canal 

 tra\''erses the petro-tympanic chamber as in Tarsius; the lachrymal and malar do not unite on the anterior rim of the orbit; 

 the digital lengths of the manus are not known with certainty; but in Nothardus the e>'idence is reasonably conclusive that 

 the fourth w^as not longer than the third. 



On the other hand, their resemblance to the Paleopithecini [Tarsius, AnaptomorpJnis and their allies] is more marked. 

 This is seen in the greatly inflated condition of the tympanic bulte as well as in the outward and backward extension of the 

 external alte of the pterygoids. These forms differ from the Paleopithecini, however, in having a more reduced lachrymal, 

 in the position of the external opening of the lachrymal canal on or near the rim of the orbit, in having a greater number of 

 premolars, and in general in being larger and of more robust proportions. Thus, it will be seen that they occupy a position 

 intermediate in many respects between the remaining Anthropoidea and the Paleopithecini. In the latter, there seems to 

 have been a marked tendency toward precocious specialization in both tooth reduction and brain enlargement, which are 

 curiously associated with retention of the primitive condition of the lachrymal. Adapis and Nothardvs, on the other 

 hand, exhibit advance in the reduction of the lachrymals, but retain the more generalized features of the dentition and 

 brain enlargement. These are the essential differences between the two lines and mark out very distinctly the trend as 

 well as the possibilities of their future development. It is in just such a group as that which includes Adapis, Nothardus 

 and Limnotherinrn, that we must seek for the beginnings of the higher monkeys and apes which follow; and while these 

 species, at present the only well-known types of the series, may not ha\ e been in the direct line of descent, they can not 

 at the same time have been far removed from it (p. 410). 



Here, then, was an important conclusion as to the relationships of Notharctus and its aUies, namely, 

 that they could not be referred to the Lemuroidea and that they belonged to a group in which we must 

 seek the beginnings of the higher monkeys and apes. As already noted, Leidy in 1873 had observed the 



