MYLODON. 
29 
MYLODON. 
(Mylodon robustus .) 
The Sloth tribe was represented during the geological period immediately preceding the 
present by several gigantic Edentates. Among them, and second only to the Megatherium, is 
the Mylodon, whose fossil remains were discovered in 1841, buried twelve feet deep in the 
fluviatile deposits seven leagues north of the city of Buenos Ayres. It forms the subject of 
an elaborate memoir by Professor Owen. The skeleton, as mounted in the Royal College of 
Surgeons at London, measures eleven feet from the muzzle to the end of the tail, thus indica- 
ting a size about equal to that of the Hippopotamus. But the bones are more than propor- 
tionally massive. The pelvis, as broad as, and deeper than, that of the Elephant, rests on two 
massive, but short hind extremities, terminated by feet as long as the femora, set at right 
angles to the legs, as in plantigrade animals, but with the sole slightly turned inwards. The 
breadth of the largest caudal vertebrae is over 10 inches; length of os calcis, inches; greatest 
circumference of the head of the femur, 15 inches; circumference of the trunk outside of the 
tenth pair of ribs, 8 feet and 2 inches; greatest length of scapula, 19 inches; length of clavicle, 
8 inches; length of fore-foot, 14 inches; extreme length of skull, I 82 inches. JThe skull, though 
smaller than that of the Ox, is long and narrow; and the lower jaw is wider than that of the 
Megatherium. The Mylodon had no proboscis, but the compensation was a very largely 
developed tongue. The palate was five inches wide, that of the Megatherium being only two. 
The teeth, simple, long, and fangless, resemble in structure those of its greater contemporary, 
but differ somewhat in shape, and in containing a less proportion of cement. The formula is 
M. 1 4 = 18 ; the first molar being separated like a canine. All the true ribs are clamped by 
ossified cartilages to a complicated sternum. The fore-foot is penta-dactyle; the hind-foot, 
tetra-dactyle. The lumbar vertebra are anchylosed to each other and to the sacrum; and the 
tibia to the fibula. There are seven vertebra in the sacrum, and twenty in the tail. The 
Mylodon was a vegetable feeder, and from the conformation of its fore-feet and arms, as well 
as that of its hind extremities and strong thick tail, it is supposed that it sat in an upright 
position, stripping the trees of their leaves and tender branches. 
