Nor they were formed by any known geological process.
But their creators have left evidence all around the walls and ceilingsgiant claw marks.
A large paleoburrow in Brazil.
Up until then, little was known or written about these tunnels in scientific literature.
Some of these burrows measure hundreds of feet long and branched off into several direction.
The largest one measured 2,000 feet long, six feet tall and three to five feet wide.
An estimated 4,000 metric tons of dirt and rock were dug out of the hillside to create the burrow.
It was evidently the work of not one or two individuals but several generations.
They were some of the biggest land mammals on earth exceeded in size only by the mammoth.
Others believe that extinct armadillos, which were smaller than the giant sloths, were responsible for the burrows.
Claw marks on the sides of the burrow.
The paleoburrows also have a strange geographic distribution.
They have been found only in the southern Brazilian states of Rio Grande do Sul and Santa Catarina.
Very few have been found in northern Brazil, or in other South American countries.
The fact that we dont have them here could simply be that weve overlooked them, he says.
There are still a lot of unanswered questions surrounding the paleoburrows and its creators.
Why they were built?
How they were built, and when?
Inside the first paleoburrow discovered in the Amazon.
Photo credit: Heinrich Frank
Outside the entrance to a paleoburrow.
Photo credit: Heinrich Frank
Megatherium americanum, the giant sloth.
