Sloth Relatives Part Three: Extinct Relatives (Ancestor Sloths)

Up until about 10,000 years ago, instead of the small tree-dwelling sloths, sloths were giant ground-dwelling creatures, with a few marine relatives.  Megatherium americanum was the size of an elephant.  Eremotherium emigrants had claws that were up to a foot long!  

There were many more sloths at time; the fossil records show over 50 different sloth species.  What happened to all the giant ground sloths?  Without a time machine we don’t know for sure, but the theory is that humans caused the mass extinctions, with possible contributions from an ice age.

Megatherium americanum (giant sloth) skeleton in a natural history museum.

Restoration of the Shasta Ground Sloth (Nothrotheriops shastense) by FunkMonk (Michael B.H.)

Thalassocnus marine-sloth skeleton in its hypothetical swimming pose, Muséum national d'histoire naturelle, Paris, photo by FunkMonk

Here are some interesting articles on sloth evolution, for further reading:

Slothful trends in evolution:  From walking giants to tiny tree-dwellers

Sloth Evolution Not So Slothful After All

The Sloth's Evolutionary Secret

The Giant Swimming Sloths of South America