Appendix S2. List of specimens observed for the purpose of comparison. Asterisks represent specimens observed through high-quality photographs. TAXON CODE COUNTRY SITE/AGE DESCRIPTION Baraguatherium takumara IVIC-P-2917 Venezuela Cerro la Cruz - early Right femur without proximal epiphysis Miocene Bolivartherium urumaquense MCN 170-72V Venezuela Urumaco - late Miocene Cranial fragment, two maxillary fragments, mandibles, ulna, astragalus, sacrum and other fragments (type) Bradypus sp. AMNH 16871 ? Extant Complete skeleton Bradypus sp. MACN Ma 4.125 Paraguay Extant Complete skeleton Catonyx sp. MACN Pv 16639 Argentina Buenos Aires - Pleistocene Two femorae, left ulna, partially reconstructed right scapula, left tibia, calcaneum Catonyx tarijensis FMNH P14225 Bolivia Tarija - Pleistocene Left radius, ulna, scaphoid, lunar, cuneiform and magnum Catonyx tarijensis FMNH P14238 Bolivia Tarija - Pleistocene Complete skeleton Glossotheridium chapadmalense MACN Pv 10156 Argentina Miramar - Pliocene Left humerus Glossotherium robustum MACN Pv 62 Argentina Pleistocene - no locality Left humerus Glossotherium robustum AMNH 11271 Argentina Arroyo Balta - Pleistocene Mounted skeleton Glossotherium robustum MACN Pv 10606 Argentina Balcarce - Arroyo Grande - Proximal fragment of radius Pleistocene Glossotherium robustum MACN Pv 999 Argentina Buenos Aires - Pleistocene Complete skeleton Glossotherium robustum AMNH 11275 Argentina Buenos Aires - Pleistocene Complete forelimb and manus (mounted specimen) Glossotherium robustum AMNH 11276 Argentina Buenos Aires - Pleistocene Left femur Glossotherium robustum AMNH 11307 Argentina Buenos Aires - Pleistocene Left humerus Glossotherium robustum MACN Pv 12095 Argentina Buenos Aires - Pleistocene Right ulna Glossotherium robustum MACN Pv 18656 Argentina Buenos Aires - Pleistocene Right humerus, fragment of femur, proximal fragment of ulna, caudal vertebrae and other fragments Glossotherium robustum MACN Pv 4423 Argentina Buenos Aires - Pleistocene Right humerus Glossotherium robustum MLP 3-237 Argentina Buenos Aires - Pleistocene Proximal fragment of left ulna Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Right humerus 123 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Right femur 125 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Right femur 128 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Right tibia 132 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Left tibia 135 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Almost complete four autopodia 141 Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Left ulna 141 (A.C. 7069) Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Right fibula 141 (A.C. 7111) Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Left fibula 141 (A.C. 7112) Glossotherium robustum MNHN.F.PAM Argentina Buenos Aires - Pleistocene Incomplete right pes 144 Glossotherium robustum MACN Pv 14760 Argentina Córdoba - Pleistocene Proximal fragment of left scapula Glossotherium robustum MACN Pv 17572 Argentina Entre Ríos - Pleistocene Two incomplete humeri, fragments of femur, tibia, radius, astragalus, scapula and bones of manus and pes Glossotherium robustum MLP 3-140 Argentina Luján - Buenos Aires - Complete skeleton Pleistocene Glossotherium robustum MLP 3-139 Argentina Olavarría - Upper Complete skeleton (juvenile) Pleistocene Glossotherium robustum MNHN.F.R 269 ? Pleistocene - no locality Left tibia Glossotherium robustum MACN Pv 1321 Argentina Pleistocene - no locality Several appendicular bones (juvenile) Glossotherium robustum MACN Pv 14066 Argentina Pleistocene - no locality Left scapula Glossotherium robustum MACN Pv 14070 Argentina Pleistocene - no locality Left ulna Glossotherium robustum MACN Pv 91 Argentina Pleistocene - no locality Atlas, axis, patella, ulna, radius, calcaneum and bones of the pes Glossotherium robustum MLP 3-114 Argentina Pleistocene - no locality Right tibia Glossotherium robustum MLP 3-128 Argentina Pleistocene - no locality Right tibia Glossotherium robustum MLP 3-188 Argentina Pleistocene - no locality Complete skeleton Glossotherium robustum MLP 35-III-10-1 Argentina Pleistocene - no locality Right tibia Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Right humerus 141 (A.C. 7068) Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Left humerus 118 Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Left humerus 119 Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Left humerus 122 Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Left humerus 141 (A.C. 7067) Glossotherium robustum MNHN.F.PAM Argentina Pleistocene - no locality Right ulna 141 (A.C. 7070) Glossotherium robustum MNHN.F.PAM s/n Argentina Pleistocene - no locality Left radius (1) Glossotherium robustum MNHN.F.PAM s/n Argentina Pleistocene - no locality Right radius (2) Glossotherium robustum MACN Pv 10120 Argentina Río Carcarañá - Santa Fe - Various manus fragments Pleistocene Glossotherium robustum MACN Pv 11331 Argentina Río Carcarañá - Santa Fe - Various manus and pes fragments Pleistocene Glossotherium robustum MACN Pv 11421 Argentina Río Carcarañá - Santa Fe - Various manus and pes fragments Pleistocene Glossotherium tarijense MNHN.F.TAR 767 Bolivia Tarija - Pleistocene Right humerus Glossotherium tarijense MNHN.F.TAR 787 Bolivia Tarija - Pleistocene Right tibia Glossotherium tarijense MNHN.F.TAR 788 Bolivia Tarija - Pleistocene Right tibia Glossotherium tarijense MNHN.F.TAR 789 Bolivia Tarija - Pleistocene Right tibia Glossotherium tarijense MNHN.F.TAR 790 Bolivia Tarija - Pleistocene Left tibia Glossotherium tarijense MNHN.F.TAR 792 Bolivia Tarija - Pleistocene Right tibia Glossotherium tarijense MNHN.F.TAR 793 Bolivia Tarija - Pleistocene Right tibia Glossotherium tarijense MNHN.F.TAR 794 Bolivia Tarija - Pleistocene Right humerus Glossotherium tropicorum VF-11 Venezuela Muaco - late Pleistocene Left femur Glossotherium tropicorum VF-205 Venezuela Muaco - late Pleistocene Right mandible Glossotherium tropicorum VF-24 Venezuela Muaco - late Pleistocene Right ulna Glossotherium tropicorum VF-26 Venezuela Muaco - late Pleistocene Right humerus Glossotherium tropicorum VF-28 Venezuela Muaco - late Pleistocene Right radius Hapalops cf. ruetemeyeri FMNH P13128 Argentina Santa Cruz Fm. - late early Mandibles, proximal fragment of humerus, Miocene left femur, tibia, fibula Hapalops elongatus MACN Pv 11766 Argentina Chubut - Pampa del Castillo Distal part of right humerus Hapalops elongatus FMNH P13123 Argentina Santa Cruz Fm. - late early Radius, proximal fragment of ulna and Miocene complete patella, tibia, fibula, calcaneum, astragalus, navicular, cuboid, and phalanges Hapalops elongatus FMNH P13133 Argentina Santa Cruz Fm. - late early Cranium, mandible, left and right humeri, Miocene scapula, radius, ulna Hapalops ruetemeyeri FMNH P13130 Argentina Santa Cruz Fm. - late early Mandibles, right humerus, ulna, radius, left Miocene femur, tibia, one vertebra, phalanges and mtc4 Lestobradys sprechmanni MNHN 1641* Uruguay Camacho Fm. - late Miocene Right astragalus Lestodon armatus MACN Pv 10747 Argentina Barrancas Mar del Plata - Left cuboid early Pleistocene Lestodon armatus MACN Pv 10748 Argentina Barrancas Mar del Plata - Right cuboid early Pleistocene Lestodon armatus MACN Pv 10749 Argentina Barrancas Mar del Plata - Right navicular early Pleistocene Lestodon armatus MACN Pv 10750 Argentina Barrancas Mar del Plata - Mtt3 right early Pleistocene Lestodon armatus MACN Pv 10751 Argentina Barrancas Mar del Plata - Mtt3 right early Pleistocene Lestodon armatus MACN Pv 10752 Argentina Barrancas Mar del Plata - Mtt4 left early Pleistocene Lestodon armatus MACN Pv 10754 Argentina Barrancas Mar del Plata - Mtc4 left early Pleistocene Lestodon armatus MACN Pv 10755 Argentina Barrancas Mar del Plata - Mtc3 right early Pleistocene Lestodon armatus MACN Pv 10756 Argentina Barrancas Mar del Plata - Right unciform early Pleistocene Lestodon armatus MACN Pv 10757 Argentina Barrancas Mar del Plata - Left lunar early Pleistocene Lestodon armatus MACN Pv 10758 Argentina Barrancas Mar del Plata - Right lunar early Pleistocene Lestodon armatus MACN Pv 10759 Argentina Barrancas Mar del Plata - Mtc3 right early Pleistocene Lestodon armatus MACN Pv 10760 Argentina Barrancas Mar del Plata - Mtc5 left early Pleistocene Lestodon armatus MACN Pv 10761 Argentina Barrancas Mar del Plata - Left unciform early Pleistocene Lestodon armatus MACN Pv 10762 Argentina Barrancas Mar del Plata - Left magnum early Pleistocene Lestodon armatus MACN Pv 10763 Argentina Barrancas Mar del Plata - Left magnum early Pleistocene Lestodon armatus MACN Pv 10789 Argentina Barrancas Mar del Plata - Mtt2 right early Pleistocene Lestodon armatus AMNH 11310 Argentina Buenos Aires - Pleistocene Postcranial elements (atlas, astragalus, humerus, tibia) Lestodon armatus AMNH 96233 Argentina Buenos Aires - Pleistocene Postcranial elements (scaphoid, unciform, cuneiform, mtc3, mtc4, navicular, cuboid, lunar) Lestodon armatus MACN Pv 14615 Argentina Buenos Aires - Pleistocene Left radius Lestodon armatus MACN Pv 14616 Argentina Buenos Aires - Pleistocene Right radius Lestodon armatus MACN Pv 14648 Argentina Buenos Aires - Pleistocene Complete right scapula Lestodon armatus MACN Pv 14653 Argentina Buenos Aires - Pleistocene Right radius Lestodon