Hendrik N. Poinar, Fabien L. Condamine, Frédéric Delsuc, Mariella Superina, Melanie Kuch, Jacob Enk, Gillian C. Gibb, Nadia Moraes-Barros, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, University of Alberta, Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden, McMaster Ancient DNA Centre, Department of Anthropology, McMaster University, Hamilton, ON, Canada, Instituto de Biociências, Universidade de São Paulo (USP), Instituto de Biociências, Universidade de São Paulo, Biological Science Department, University of New Orleans, New Orleans, This work largely benefited from the help of the following individuals and institutions who provided tissue samples: François Catzeflis (Institut des Sciences de l’Evolution, Montpellier, France), Jean-François Mauffrey, Philippe Gaucher, Eric Hansen, François Ouhoud-Renoux, Jean-Christophe Vié, Philippe Cerdan, Michel Blanc, and Rodolphe Paowé (French Guiana), Sergio Vizcaíno (Museo de La Plata, La Plata, Argentina), Jorge Omar García and Rodolfo Rearte (Complejo Ecológico Municipal, Presidencia Roque Sáenz Peña, Argentina), Daniel Hernández (Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay), John Trupkiewicz (Philadelphia Zoo, USA), Darrin Lunde (National Museum of Natural History, Washington, USA), Jim Patton and Yuri Leite (Museum of Vertebrate Zoology, Berkeley, USA), Ross MacPhee (American Museum of Natural History, New York, USA), Jonathan Dunnum and Joseph Cook (Museum of Southwestern Biology, Albuquerque, USA), Donna Dittman and Mark Hafner (Louisiana State University Museum of Natural Science, Baton Rouge, USA), Gerhard Haszprunar and Michael Hiermeier (Zoologische Staatssammlung München, Munich, Germany), Géraldine Véron (Museum National d’Histoire Naturelle, Paris, France), Agustín Jiménez-Ruiz, Guido Valverde, and Guillermo Pérez-Jimeno. Our thanks also extend to Trish McLenachan and David Penny who sequenced and made freely available the first sloth mitogenomes, Lionel Hautier and Philippe Gaubert for taxonomical advice, and two anonymous referees for helpful comments. This work was supported by grants from the EU’s Seventh Framework Programme (No 286431) to N.M.-B., the Centre National de la Recherche Scientifique (CNRS), the Scientific Council of Université Montpellier 2 (UM2), and Investissement d’Avenir of the Agence Nationale de la Recherche (CEBA: ANR-10-LABX-25-01) to F.D., and the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Research Chairs program to H.N.P. This is contribution ISEM 2015-227-S of the Institut des Sciences de l’Evolution de Montpellier, ANR-10-LABX-0025,CEBA,CEnter of the study of Biodiversity in Amazonia(2010), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS), University of Gothenburg (GU), McMaster Ancient DNA Center [Hamilton, Ontario], McMaster University [Hamilton, Ontario], and University of New Orleans