FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. 173 



tain arctocyonids, Claenodon belongs in the Arctocyoninae. Deutero- 

 gonodon might be placed there or in the Oxyclaeninae, or even in the 

 Condylarthra. In default of better evidence and for ease of subfamily 

 recognition it is placed in the Arctocyoninae, which it most resembles 

 in adaptive characters although perhaps not phyletically close to 

 other members of that group. 



Alimotricentes is a typical but well-differentiated oxyclaenine. 

 Prothryptacodon seems surely to be in the lineage of Thryptacodon, 

 with which it forms a rather distinctive phylum retained in the 

 Oxyclaeninae, where Thryptacodon has generally been placed. Meta- 

 chriacus is an oxyclaenine in the broad sense. If Oxyclaeninae and 

 Chriacinae were separated, this genus would be incertae sedis, for it 

 resembles both groups. Spanoxyodon is also clearly oxyclaenine, 

 sensu lato, and might doubtfully be an aberrant chriacine if that 

 group were retained. The occurrence of Chriacus in the fauna is 

 possible, but not proved, and no additional evidence on the affinities 

 of that genus is here adduced. Coriphagus, with which the Torrejon 

 Mixoclaenus is synonymous, was classified by Matthew in the Oxy- 

 claeninae, but I believe it to be an anisonchine, as set forth in dealing 

 with that group. 



The members of this family are the most primitive of known carni- 

 vores, and, as might be expected, they are abundant in all Lower and 

 Middle Paleocene faunas. In the Upper Paleocene they are less 

 varied and comm.on, and as far as known they died out by the end of 

 lower Eocene time. The Middle Paleocene forms are prototypal in 

 a general, structural sense, but are already too late to be ancestral 

 to other groups. Matthew (Pale. Mem.) has pointed out the great 

 interest of the family as probably including in its Lower Paleocene or, 

 especially (unknown), pre-Paleocene members the probable ancestry 

 not only of all carnivores but also of other orders, including most or 

 all ungulates and some others. Despite the numerous minor struc- 

 tural modifications, most members of the family have almost diagram- 

 matic tuberculo-sectorial teeth such as are believed to be primitive 

 for all marsupial and placental mammals. The osteological characters 

 of the group as a whole are also primitive for the great majority of 

 placental mammals, many of them for all these, but on these characters 

 the present materials have practically nothing to add to what is known 

 from the Puerco and Torrejon mammals. 



Subfamily Arctocyoninae Giebel, 1855 



Claenodon and Deuterogonodon represent this subfamily in the 

 present fauna. The status of a supposed third genus, Neoclaenodon, is 

 discussed below. Deuterogonodon might be considered an oxyclaenine, 

 in view of its resemblance to Protogonodon, which Matthew so classi- 



