FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 71 



Dr. Gidley had evidently formed definite conclusions as to the 

 classification of the whole group in the Fort Union collection, for most 

 of the labels bear specific names, several of them new. Two or three 

 of the new species described below correspond approximately with 

 some of those recognized by Gidley, but as the correspondence is not 

 exact even in these cases and as my classification is otherwise much 

 unlike that suggested by Gidley's labels, it is evident that he did not 

 emplo}^ the criteria here used. As he left no notes or manuscript 

 relating to this group, I am forced to treat it de novo (except, of 

 course, for his preliminary publication). 



As shown by the figures given elsewhere, multituberculates made 

 up a large proportion of the collection and are the most important 

 single element in the fauna. 



AFFINITIES OF THE MULTITUBERCULATA 



This material has had such a decisive influence in the consideration 

 of the affinities of the Multituberculata that the subject must be 

 mentioned briefly here, although it has been thoroughly reviewed 

 elsewhere (Simpson, 1929c, 1929e; Simpson and Elftman, 1928; 

 Granger and Simpson, 1929). 



The earliest ideas (Falconer; Owen; Marsh; Cope, 1884; Osborn, 

 1888), influenced by the descriptive analogy of the shearing teeth to 

 those of some diprotodont marsupials (and a few other inconclusive 

 characters), were that the multituberculates were marsupials. When 

 the teeth of Ornithorhynchus were discovered, Cope saw in them 

 some resemblance to the multituberculates and suggested that the 

 latter were monotremes.^^ 



When the fine specimen of Ptilodus here redescribed was discovered, 

 it gave Dr. Gidley the first real opportunity to study the problem on 

 a broader basis than that aftorded by the often misleading dental 

 characters. After a careful, but only provisional, analysis, he con- 

 cluded that Ptilodus and the other multituberculates are diprotodont 

 marsupials, diverging from those of Australia in the Jurassic or even 

 in the earlier Triassic.^* 



Broom (1910) restudied Tritylodon and critically examined Gidley's 

 publication, concluding that the multituberculates were an indepen- 

 dent group without near affinities with the living monotremes, mar- 

 supials, or placenta,ls. Later (1914) Broom studied Gidley's original 

 and also a skull of Taeniolabis and then concluded that the multi- 

 tuberculates were monotremes. 



23 A few theories unworthy of further serious consideration are passed over without any notice. All 

 have been listed and refuted in previous papers. 



2< This and several other points in his Fort Union work demonstrate Gidley's belief in the extreme antiquity 

 of modern groups of mammals and their polyphyletic evolution. This philosophical consideration underlay 

 much of his work and colored many of his conclusions. Specifically, he believed the Australian mammals 

 to have been differentiated in the Mesozoic and outside of Australia. See also Myrmecoboides, below. 



119212—37 6 



