A new study by scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), has revealed significant cryptic diversity within two-toed sloths (Choloepus) in Amazonia, challenging the long-established taxonomy of the genus. This international effort involved key South American collaborators. Utilizing the first genome-wide dataset from multiple two-toed sloth populations, the study published in the journal “Molecular Phylogenetics and Evolution” provides critical new evidence that past environmental changes shaped the sloths’ evolutionary history, and highlights an urgent need for taxonomic revision and updated conservation assessment and strategies.