loo AMERICAN MESOZOIC MAMMALIA 



Order MULTITUBERCULATA 



Cope 1884 



Suborder PLAGIAULACOIDEA Simpson 1925 



This order and suborder have been defined above. All of the upper Cretaceous 

 multituberculates are apparently referable to the single family Ptilodontidae. 



PTILODONTIDAE Simpson 1927 



Definition.— Dental formula \l\\\% . Enlarged incisors rooted, with extra- 

 alveolar portion almost completely enameled or v^^ith restricted enamel band extending 

 (in youth) into the alveolus. P3, when present, small, one-rooted, fitting into a notch in 

 P4. P4 large, laterally compressed, trenchant, with serrate edge and lateral ridges. 

 Anterior upper premolars not opposed by lower teeth, grasping, with three to six coni- 

 cal cusps. Only the last upper premolar shearing in function, enlarged. M^ with three 

 cusp rows, the inner usually incomplete anteriorly; M^ with three cusp rows, the outer 

 always incomplete posteriorly. Molar cusps more or less crescentic. Wear not reducing 

 molar surfaces to planes but accentuating longitudinal ridges and grooves. First 

 molars much larger than second. Skull triangular as seen from above. Animals 

 usually of small size relative to Taeniolabididae. 



Type. — Pttlodus Cope. (Paleocene.) 



Distribution. — Upper Cretaceous of Mongolia and North America. Paleocene 

 of Europe and North America. Eocene of North America. 



This is the largest and best known of all multituberculate families. So far as pres- 

 ent records show, its greatest development was in the Paleocene when it was probably 

 world-wide," but in North America, at least, it survived into the true Eocene {Eucos- 

 modon ultimus Granger and Simpson, 1928) and the upper Cretaceous multitubercu- 

 lates cannot be excluded from it. Cimolomys certainly belongs here, but some of the 

 other forms, such as Meniscoessus and Djadochtatherium are more provisionally 

 referred. 



Paronychodon Cope 1 876 

 1876. Paronychodon, Cope, Proc. Ac. Nat. Set. Phila., 1876, 256. 



Definition. — With compressed, grooved lower incisors like those of Meniscoes- 

 sus. 



Type. — P. lacustris Cope. 



^° It is not known from Africa or from South America, but no mammal-bearing Paleocene deposits 

 are as yet known in either continent. The Polydolopids are not multituberculates and the fauna in which 

 they occur, the so-called Notostylops fauna, is almost surely of middle or upper Eocene age. 



