rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 161 



Family CARPOLESTIDAE Simpson, 1935 



As was pointed out in describing Carpolestes (Simpson, 1928, p. 

 10), Elphidotarsius supplies a good morphological ancestry for the 

 very peculiar and aberrant genera Carpodaptes Granger and Matthew 

 of the Tiffany and Carpolestes Simpson from Tiffany or slightly later 

 equivalents in the Fort Union. The present opportunity to compare 

 the genotypes of the three genera at first hand fully confirms this and 

 leaves no doubt that they are closely related. 



Elphidotarsius and Carpolestes show the same highly characteristic 

 basic structure throughout P4-M3. Carpodaptes has P4 more enlarged 

 than in Elphidotarsius, its apical cuspules all in a straight line and one 

 more in number. On Mi the trigonid is still more elongate, and the 

 paraconid almost directly anterior to the protoconid. Oth^er struc- 

 tural distinctions are very slight and unimportant. In Carpolestes P4 

 is still larger, its cuspules increased to seven or eight, its heel elevated 

 to the trigonid level of Mj. On Mi the paraconid and protoconid are 

 exactly in the same longitudinal line and continue without a break 

 the cuspule series of P4. The structural sequence Elphidotarsius- 

 Carpodaptes-Carpolestes is almost perfect (also in the size of the 

 known species) and may be a direct phylogeny, although the possible 

 age difference between the last two genera seems too small to permit 

 such a marked structural advance in a direct descendant, and it is 

 more likely that some collateral evolution is involved. 



Upper teeth are as yet known only in the genera Carpolestes (Car- 

 polestes dubius Jepsen; see Jepsen, 1930a) and Carpodaptes. The 

 molars are of primitive tritubercular type, with distinct hypocone, 

 more or less closely paralleled in some primitive Eocene primates 

 (e. g., Omomys, Caenopithecus, Pseudoloris, and others). P^~*, how- 

 ever, are very extraordinary and unlike anything known in any other 

 primate or indeed any placental mammal, to such a degree that when 

 the first isolated example of one of these teeth was found I hesitantly 

 referred it to the Multituberculata {" Lifotherium" ®^ Simpson, 1929, 

 p. 9), and this remarkably bad guess was onlj?^ corrected when Jepsen 

 found associated premolars and molars. Like the last premolar of 

 Ptilodus, both P^ and P* have tliree longitudinal rows of cusps. 



These premolars are much unlike those of any tarsioid, as is P4, but 

 it may confidently be predicted that P^-* of Elphidotarsius, when 

 found, will distinctly approach the normal tarsioid type, as does P4 

 of that genus. P ^~* of Carpodapttes are indeed closer to Carpolestes, 

 but they show some approach to more norm^al structure. 



«» A strict synonym of Carpoteslcs Simpson, 1928. The retention of Carpolestes as the definitive name is 

 not only preferable, as Jepsen suggests, but also the only possible course in accordance with the rules of 

 nomenclature. 



