The sloth family tree once sported a dizzying array of branches, body sizes and lifestyles, from small and limber tree climbers to lumbering bear-sized landlubbers. Why sloth body size was once so ...

Imagine a sloth. You probably picture a medium-sized, tree-dwelling creature hanging from a branch. Today's sloths—commonly featured on children's backpacks, stationery and lunch boxes—are slow-moving ...

Giant sloths with razor-sharp claws and as large as Asian bull elephants once roamed the Earth, snacking on leaves at the tops of trees with a prehensile tongue. Now, scientists have figured out why ...

Sloths look simple from a distance: slow mammals, quiet days in trees, same route, same rhythm. That picture is wrong in useful ways. The group itself is more diverse than most people assume, with two ...