232 BULLETIlsr 16 9, UNITED STATES NATIONAL MUSEUM 



Subfamily MiocLAENiNAE Matthew (ex ms.) (Mioclaenidae Osborn 



and Earle, 1895) 



Bevised definition. — Paleocene hyopsodontid condylarths with P^4 

 more or less enlarged and sometimes inflated. P4 generally relatively 

 simple, with small talonid. Molar paraconids reduced, internal, 

 fusing with metaconids. Molar talonids generally open, entoconids 

 reduced, fusing with hj^poconulid and becoming vestigial. M^3 

 often more or less reduced. M^~^ with very weak or no hypocone, 

 posterior cingulum tending to run to tip of protocone. 



This subfamily is redefined to include Mioclaenus, its structural 

 ancestor Choeroclaenus , Ellipsodon, and (doubtfully) Litaletes, and to 

 exclude Protoselene, Oxyacodon, and some other genera formerly 

 placed in it. Choeroclaenus does not occur in the fauna here under 

 discussion, but it is defined below because reconsideration of the whole 

 family demands the proposal of this new name. Ellipsodon and 

 Litaletes have species in this fauna and are further considered in con- 

 nection with these species. 



CHOEROCLAENUS ^s, new genus 



Type. — Mioclaenus turgidunculus Cope, 1888. 

 Distribution.- — Lower Paleocene, Puerco, New Mexico. 

 Diagnosis. — P'*4 bulbous, inflated. P4 without anterior cuspule, 

 paraconid or metaconid, talonid very small, wdth one faintly crested 

 cuspule. Molar paraconids small but distinct, nearly confluent with 

 metaconids but not wholly internal. Entoconids distinct and about 

 as high as hypoconulids, molar talonids basined. M^3 little or not 

 reduced. M3 with projecting hypoconulid. M^~^ transverse, with 

 sharp external, anterior, and posterior cingula. Hypocone indistinct, 

 posterior cingulum tending to connect with protocone tip, M^ with 

 well-developed metacone. Connies small, distinct. Cusps low but 

 sharp and clear-cut, crenulations and proliferation of minor cuspules 

 slight or absent. 



Discussion. — The type species rather closely resembles the type of 

 Mioclaenus, M. turgidus, and has almost invariably been referred to 

 that genus.^^ It is, however, sharply distinguished by the characters 

 given above and in the key on a previous page. Most of these dis- 

 tinctions are primitive characters, and they tend to link this form, 

 more nearly than the later and more aberrant Mioclaenus turgidus, to 

 the small and more generalized early hyopsodontids. Matthew, the 

 only person who had critically examined the specimens since Cope, 

 recognized this and recorded it (Pale. Mem.) by transferring the species 

 to the primitive genus Oxyacodon, a structurally defensible and reason- 

 's XoTpos, pig, + claenus, a combination meant to suggest the dental resemblance to bunodont artiodactyls, 

 relationship to Mioclaenus, and derivation from the Puerco beds. 



'• The single exception, previous to Matthew's last work, seems to be Roger, who placed it in Protogonodon 

 in his catalog, but the reason for this is not apparent. 



