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   Who carved South America's mysterious ancient tunnels? [pdf] (clp.unesp.br)
Giant sloths was not really on my list of expected answers but "One species, Glossotherium robustum, a South American sloth that lived between 4 million and 12,500 years ago, reached more than 3 metres in length and weighed up to 1,500 kilograms"

But who was really in charge?

I wish there were more pictures.