SYSTEMATIC DESCRIPTION OF GENERA AND SPECIES 



The classification of the Merycoidodontidje may be stated as follows: 



Class Mammalia 



Subclass Monodelphia 

 Superorder Ungulata 

 Order Artiodactyla 

 Suborder Ancodonta 



Superfamily Merycoidodontoidea 

 Family Merycoidodontida; 



Genera Protoreodon, Hyomeryx, Bathygenys, Oreonetes, Limnenetes, Merycoido- 

 don, Eucrotaphus, Eforeodon, Mesoreodon, Protnerycochoerus, Merycochcerus, 

 Pronomot/ierium, Alerycoides, Paroreodon, P/ienacoccelus, Tkholeftus, Poatrefhes, 

 Metoreodon, Oreodontoides, Aderyc/iyus, Leptauchenia, Cyclofidius. 



Family MERYCOIDODONTID^E 



The family characters are as follows: Dentition selenodont; dental formula typically 3 , }, 4 , \, 

 with incisors reduced in some highly specialized forms; Pi caniniform and c incisiform; tooth 

 row a closed series; ant orbital pit present and orbit closed, except in early forms; skull vacuities 

 present in specialized genera; bulla; small to very large; skull typically mesocephalic but occasion- 

 ally dolichocephalic and brachycephalic; feet functionally tetradactyl, with ungues hoofed; body 

 long; tail long to short; size small to medium, never large; range of age upper Eocene to middle 

 Pliocene; habitat North America only. 



Genus PROTOREODON Scott and Osborn 1887 

 Table 1 



Original Reference: Preliminary report on the vertebrate fossils of the Uinta formation, collected by 

 the Princeton expedition of 1886. Proc. Amer. Philos. Soc, XXIV, p. 257. 

 Synonyms: Eomcryx Marsh 1875; Agr'wtherium Scott 1898. 

 Genotype: P. parvus Scott and Osborn 1887. 

 Genoholotype: Cat. No. 10398 P.U.M., palate and fragment of left ramus. 



Distinguishing Characters: Skull dolichocephalic to mesocephalic, length between 

 129 mm. and 173 mm.; face with orbits approximately half of skull length; muzzle short, nar- 

 row, and abruptly truncate anteriorly; nasals long, narrow, and very convex transversely, extending 

 in advance of premaxillse; frontals narrow but unreduced, moderately decurved above orbits; 

 malar long, extending nearly to glenoid and not notched for reception of anterior of squamous por- 

 tion of arch; zygomatic arch slender, nearly uniform in depth and nearly parallel with tooth row; 

 antorbital fossa lacking; orbits posteriorly open and medium-sized; palate of nearly uniform 

 width; brain case long, low, and narrow; occiput narrow; supraoccipital crest moderately produced 

 and sagittal crest high, thin, and narrow; bulla? tiny, with tubular meatus; infraorbital foramen 

 over P 3 generally but in some species over interval between P 3 and P 4 ; angle of mandible not 

 prominent; coronoid moderately long and recurved; condyle not far above tooth level and located 

 above angle; masseteric fossa extending below level of alveolar parapet; symphysis sometimes 

 coossified. 



