Unable to identify any natural geological explanation for the cave’s existence, he eventually concluded that it was a “paleoburrow,” dug, he believes, by an extinct species of giant ground sloth.
“I didn’t know there was such a thing as paleoburrows,” says Frank.
“I’ve [also] seen dozens of caves that have inorganic origins, and in these cases, it’s very clear that digging animals had no role in their creation.” In his home state of Rio Grande do Sul, in the far south of Brazil, Frank has documented at least 1,500 paleoburrows so far.
In Santa Catarina, just to the north, he’s found hundreds more and counting.
He and his colleagues consider as possibilities several genera that once lived in South America and whose fossil remains suggest adaptation for serious digging: , though smaller than the sloths, were responsible for even the largest burrows.
Regardless, the sheer size of the burrows is something that Frank and his colleagues are still trying to explain.
It was in 2010 that Amilcar Adamy first investigated rumors of an impressive cave in southern Brazil.
Although many are completely filled with sediment, they remain readily apparent, standing out like dark, round knots in a dirt bank.But a preliminary inspection revealed it wasn’t the work of any natural geological process.He’d been in other caves nearby, formed by water within the same geology underlying this particular hillside.Whether prehistoric sloths or armadillos were responsible, the burrows are far larger than would be necessary to shelter the animals that dug them from predators or the elements.The giant armadillo, the largest member of the family, weighs between 65 and 90 pounds and is found throughout much of South America.