Much uncertainty has been felt about the habits of the Megatherium,
or Great Beast. It has been asked whether it burrowed or climbed, or
what it did; and difficulties have presented themselves on all sides of
the question. Some have thought that it lived in trees as much larger
than those which now exist as the Megatherium itself is larger than
the common sloth.[35] This, however, is now known to be a mistake.
It did not climb trees--it pulled them down; and in order to do this
the hinder parts of its skeleton were made enormously strong, and
its prehensile fore-legs formed so as to give it a tremendous power
over any thing which it grasped. Dr. Buckland suggested that animals
which got their living in this way had a very fair chance of having
their heads broken. While Professor Owen was still pondering over this
difficulty, the skull of a cognate animal, the Mylodon, came into
his hands. Great was his delight when he found that the mylodon not
only had his head broken, but broken in two different places, at two
different times; and moreover so broken that the injury could only have
been inflicted by some such agent as a fallen tree. The creature had
recovered from the first blow, but had evidently died of the second.
This tribe had, as it turns out, two skulls, an outer and an inner
one--given them, as it would appear, expressly with a view to the very
dangerous method in which they were intended to obtain their necessary
food.
The dentition of the megatherium is curious. The elephant gets teeth
as he wants them. Nature provided for the comfort of the megatherium
in another way. It did not get new teeth, but the old ones went on
for ever growing as long as the animal lived; so that as fast as one
grinding surface became useless, another supplied its place.