NO. 2 A STUDY OF MENISCOTHERIUM — GAZIN 5 



well-preserved material encountered at certain localities. Peculiari- 

 ties of distribution attributed to ecology within the southwestern 

 Wyoming area were cited in 1959 and 1962. 



Relationships. — In reviewing the hypotheses and conclusions as 

 to Meniscotherium relationships it may be noted that in Cope's 

 original description of Meniscotherium chamense (1874) he did not 

 make an ordinal assignment but regarded the new form as presenting 

 "a curious combination in structure of its molars of the character of 

 Palaeosyops, Hyopotamus, and Hipposyus." He probably did not 

 intend to imply, in citing the latter, any suggestion of primate relation- 

 ships because at that time he regarded Hipposyus (=Notharctus) as 

 a primitive horse with Orohippus as a synonym. In repeating his 

 description of Meniscotherium in 1877, however, Cope listed it in 

 first place among the Perissodactyla, immediately preceding "Oro- 

 therium" ( = Orohippus) in which he had included certain species of 

 Hyraco therium. 



In a further development of a systematic arrangement of peris- 

 sodactyls in 1881 (a) the genera were divided among 10 families, 

 and Meniscotherium was listed in the Chalicotheriidae along with 

 certain Eocene titanotheres, Old World Propalaeotherium and Rha- 

 gatherium, as well as the chalicotheres proper. The families as out- 

 lined were distinguished essentially by patterns of crescents and cross- 

 crests in upper and lower molars, the extent to which the premolars 

 resemble the molars, and the number of toes. The feet of Menisco- 

 therium, however, were not known at that time, so that conclusions 

 as to relationships were based entirely on the dentition, presumably 

 the upper molars only, as displayed in the type of M. chamense. 



Evidently the newer material cited later in 1881(b) included cer- 

 tain limb elements, possibly associated with tooth material, because 

 in the spring of 1882(a) Cope stated that the astragalus and 

 humerus had the characters of those of Phenacodus. As a result he 

 concluded that Meniscotherium, for which he proposed the new 

 family rank Meniscotheriidae, belonged with the Phenacodontidae 

 (including the periptychids) in the recently (1881c) erected sub- 

 order, Condylarthra, under the Perissodactyla. Meniscotheriidae 

 was distinguished by a lophodont dentition, "with external and 

 internal crescents and deep valleys." Further concern about the foot 

 structure of Phenacodus led Cope a couple of months later (1882c) 

 to remove the Condylarthra from the Perissodactyla, and place them 

 along with the Proboscidea in the new order or suborder Taxeopoda, 

 having equal rank with Hyracoidea, Amblypoda, Perissodactyla, and 



