Palaeontologist Thais Pansani stands in front the reconstructed skeleton of a giant ground sloth at the Smithsonian National Museum of Natural History in Washington, DC (Mary Conlon/AP ...

Paleontologist Thaís Pansani stands in front the reconstructed skeleton of a giant ground sloth at the Smithsonian National Museum of Natural History in Washington. (Picture credit: AP ...

SAO PAULO (AP) — Sloths weren’t always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge — up to 4 tons (3.6 metric tons) — and when startled, they brandished immense ...

SAO PAULO, Brazil (AP) — Sloths weren’t always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge – up to 4 tons – and when startled, they brandished immense claws.