382 JR. S. Lull — Pleistocene Ground Sloth 



The character of the mouth with its imperfect, though continu- 

 ously growing, dentition points to a community of feeding 

 habit with the modern tree sloths, and the general consensus of 

 opinion seems to be that the foliage of trees formed their 

 dietary staple. 



Brown* in discussing Paramylodon has this to say of its 

 habits : 



" Paramylodon seems to have been less specialized than 

 Mylodon, retaining features of the older, more primitive sloths. 

 From the long nasals it seems improbable that it had a probos- 

 cis, while the greatly inflated muzzle and the large movable 

 premaxillse indicate a large prehensile lip. The reduction of 

 the twelfth nervef shows a less specialized tongue than in 

 Mylodon. The rounded condyles, with the greater part of the 

 articular area on the ventral surface, and the aspect of the 

 foramen magnum, opening obliquely to the long axis of the 

 skull instead of backward, show that the head was carried more 

 at right angles to the vertebral column than in Mylodon. The 

 long calcaneum with posterior end resting flat on the ground, 

 and the astragalar facet looking forward, indicate a primitive 

 foot more flexible at the ankle than in the contemporaneous 

 Mylodon. 



"The sum of these characters points to a difference in feed- 

 ing habits and indicates that Paramylodon was a grazer." 



AllenJ in speaking of a mylodont jaw from Walhaumet 

 (Willamette) Kiver, Oregon, says: 



" It [the ramus] more nearly resembles M. robustus in having 

 a broad truncate lower lip, and was thus adapted more for a 

 grazing habit, while Paramylodon and M. garmani with their 

 elongate and compressed rami, were probably browsing animals 

 [italics mine]. The reduction of the humerus in the latter 

 may also be correlated with this habit, implying that it raised 

 itself up to reach for branches rather than to grub for 

 roots [but has "grubbing for roots" anything to do with 

 grazing?] . . . 



" Of the genus Mylodon, there were at least two types in the 

 North American Pleistocene, one represented by M. harlani, 

 a grazing type ; the other by M. garmani, here described, appar- 

 ently a browsing type. The one had a broad lip, heavy 

 humerus, tibial and astragalar facets of the fibula separate; the 

 other has a narrower, more compressed skull and rostrum, a 

 lighter humerus, tibial and astragalar facets not separated 

 (agreeing thus with Paramylodon). Also, as a further adapta- 

 tion to the browsing habit, certain of the dorsal vertebras have 



* Brown, B., op. cit., p. 569. 



\ " As indicated by The small condylar foramen in the skull." 



% Allen, G. M., op. cit., p. 344. 



