SUBORDER B 



XENARTHRA 



93 



Psiftacofherium Cope (Fig. 115). Upper and lower C have enamel only 

 on the front surface and are rooted. Eoots of P and M fused. 4 F. Lower 



niZ 



Psittacotherium muUifragum Cope. Lower Eocene of Torrejon beds, New Mexico. Skull and lower jaw. 



Vs- (After Wortman.) 



Eocene ; Torrejon. The skull of P. muUifragum Cope is quite well known. 

 It resembles that of Megalonyx. 



Calamodon Cope (Dryptodon Marsh). 



C with persistent pulp 



1.1.4.3. 



and resembling a rodent's canine. P and M with roots. M with four cusps 

 forming two ridges. Lower Eocene (Wasatch) ; Wyoming. Possibly also in 

 the Fort Union beds of Montana. Represented in the Middle Eocene 

 Bohnerz of Egerkingen by a single tooth, named C. europaeus by Riitimeyer. 



Stylinodon Marsh. All P and M are hypsodont without roots, and 

 having enamel only in bands. Middle Eocene (Bridger beds) ; Wyoming. 

 ^S*. mirus Marsh. 



Family 2. G-ravigrada. Giant Sloths. 



Extinct, large and plump herbivorous forms with long cylindrical skull. Zygomatic 



arch very strong, with downwardly directed process, v^-r^ • Teeth cylindrical. 



Tail unusually thick and long. Limbs stout and moderately long. Manus adapted 

 for grasping, and pes plantigrade. Astragalus flat, sometimes with a short neck 

 and distally truncated. 



The Gravigrada comprise the plumpest and clumsiest of all Edentata, and 

 are distinguished from modern sloths by their long skull, the stronger 

 zygomatic arches, -and the long unusually powerful tail serving as a prop, 

 the short, stout extremities, and frequently also by their considerable size. 

 They are found in the Tertiary and Pleistocene of South America and in 

 the Pliocene and Pleistocene of North America. 



The oldest form is the very imperfectly preserved Protobradys Ameghino 

 from the Notostylops beds of Patagonia. From the Miocene of Santa Cruz, 

 on the other hand, are known remains of all three subfamilies Megatheriinae, 



