Huge tunnels under southern Brazil and northern Argentina were potentially made by giant, Ice Age sloths for refuge and rest

…Many of the passages are longer than 600 yards (550 meters) and tall enough for an adult to walk through without bending.

The leading idea is that giant, extinct ground sloths dug these colossal shelters, turning parts of South America into a maze of underground homes…

…the tunnel walls are packed with claw marks, sometimes in three parallel grooves, right where a digging limb would bite into rock…