At https://www.earthtouchnews.com/discoveries/discoveries/these-giant-tunne… … strange smooth walled tunnels cutting into rock faces in Brazil and Argentina have long been a puzzle to locals. You can even stand up in some of them. It was thought they were formed by water dissolving rock – but this is contradicted as the walls show they were made by something with very big claws (below) …
… they are circular – and sinuous. They have claw marks. They occur in granites and sandstones which water does not dissolve. Can animals dig into granite – yet alone sandstone? In spite of that it is clear these are palaeo-burrows – but were they made by giant armadilloies or giant ground sloths. Armadilloes are quite capable of digging tunnels but giant ground sloths were bigger than rhinos (and built for burrowing). They also had enormous claws.
