FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 141 



Order PRIMATES Linnaeus, 1758 



The Fort Union primates are of exceptional interest as the oldest 

 known members of the order to which man belongs, and any light 

 that they can cast on the early history of this great group is highly 

 important. Dr. Gidley fully recognized these facts, and when the 

 arduous task of preparation was finally completed, he turned first to 

 the primates in beginning his definitive work. His previous papers 

 were all prehmmary and provisional, but he completed the primate 

 section of his proposed memoir and published it in 1923 as a separate 

 paper, later to be united with the other proposed sections into a 

 single monograph. No other section was ever finished, and the pri- 

 mate paper was Gidley's last contribution to the Paleocene." 



When these primates were discovered they were far the oldest 

 laiown. Many primates were known from the Eocene of Europe 

 and North America, but only one, Plesiadapis, was known from the 

 Paleocene, and this was considered as only very doubtfully primate 

 and is considerably younger than the Fort Union primates of Gidley's 

 collection. After Gidley's discovery, but before its publication, 

 Matthew (1915) added Nothodedes (—Plesiadapis) also from the 

 Paleocene, and in 1921 Matthew and Granger added several more 

 genera from the Tiffany, but these are all younger than Gidley's 

 material. Jepsen and I have made recent additions to the known 

 upper Paleocene primates, but only Plesiolestes Jepsen, 1930, is of an 

 age comparable to Gidley's genera, and there is no reason to suppose 

 that it is older.^^ 



It is in accord with Gidley's intention that these forms are here 

 redescribed in connection with the whole fauna, despite their publica- 

 tion previously. Tliis is the more necessary because since Gidley's 

 publication knowledge of early primates has been greatly increased 

 both by discovery and by revision, calling for reconsideration of many 

 points that he mentioned. For tliis reason, his diagnoses and discus- 

 sions are not quoted in full, but are revised in the light of the wider 

 knowledge of today and of the somewhat different conclusions to 

 which tliis has led me. 



Gidley recognized four new genera in this fauna and placed six 

 species in them. The fact that two species are based on upper jaws, 

 with lowers referred, and the other four on lower jaws, with uppers 

 referred to three of them, introduces a slight element of doiibt, but on 

 the basis of the lower jaws, at least, it is certain that six species are 

 represented and that Gidley's identifications of aU these specimens are 



" With the minor exception of a very brief note on the Tiffany. 



5* Abel (1931) lists Plesiolestes as from the Lower Paleocene and suggests that it is the oldest knowik 

 primate, but it is from the middle Paleocene and not appreciably, or not at all, older than the genera here 

 discussed, one of which it closely resembles. 



