Editor’s summary

Today, there are six species of sloths, all of which have similar ecologies such as arboreality and a slow metabolism. These species are a tiny remnant of a once diverse American clade that was mostly made up of large-bodied species. Boscaini et al. looked across the evolutionary history of sloths and reveal that the ancestral groups were terrestrial and large, with smaller species being derived and convergent. For 30 million years, the sloth family diversified across the Americas, from a species as large as an elephant to one that was entirely aquatic. Unfortunately, like most other large Pleistocene herbivores, the clade was almost entirely eradicated by newly arriving humans. —Sacha Vignieri

Abstract

The emergence of multi-tonne herbivores is a recurrent aspect of the Cenozoic mammalian radiation. Several of these giants have vanished within the past 130,000 years, but the timing and macroevolutionary drivers behind this pattern of rise and collapse remain unclear for some megaherbivore lineages. Using trait modeling that combines total-evidence evolutionary trees and a comprehensive size dataset, we show that sloth body mass evolved with major lifestyle shifts and that most terrestrial lineages reached their largest sizes through slower evolutionary rates compared with extant arboreal forms. Size disparity increased during the late Cenozoic climatic cooling, but paleoclimatic changes do not explain the rapid extinction of ground sloths that started approximately 15,000 years ago. Their abrupt demise suggests human-driven factors in the decline and extinction of ground sloths.

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References and Notes

1

G. G. Simpson, Splendid Isolation. The Curious History of South American Mammals (Yale Univ. Press, 1980).

2

F. Pujos, T. J. Gaudin, G. De Iuliis, C. Cartelle, Recent advances on variability, morpho-functional adaptations, dental terminology, and evolution of sloths. J. Mamm. Evol. 19, 159–169 (2012).

3

F. Pujos, G. De Iuliis, C. Cartelle, A paleogeographic overview of tropical fossil sloths: Towards an understanding of the origin of extant suspensory sloths?. J. Mamm. Evol. 24, 19–38 (2017).

4

L. Varela, S. Tambusso, R. Fariña, Femora nutrient foramina and aerobic capacity in giant extinct xenarthrans. PeerJ 12, e17815 (2024).

5

M. S. Lima-Ribeiro, S. Varela, D. Nogués-Bravo, J. A. F. Diniz-Filho, Potential suitable areas of giant ground sloths dropped before its extinction in South America: The evidences from bioclimatic envelope modeling. Nat. Conserv. 10, 145–151 (2012).

6

R. A. Fariña, S. F. Vizcaino, G. De Iuliis, Megafauna: Giant Beasts of Pleistocene South America (Indiana Univ. Press, 2013).

7

A. J. Stuart, Late Quaternary megafaunal extinctions on the continents: A short review. Geol. J. (Chichester) 50, 338–363 (2015).

8

R. D. E. MacPhee, End of the Megafauna: The Fate of the World’s Hugest, Fiercest, and Strangest Animals (W. W. Norton & Company, 2018).

9

S. F. Vizcaíno, M. S. Bargo, N. Toledo, G. De Iuliis, Conceptual challenges for the paleoecological reconstruction of the Pleistocene Pampean Megafauna and the consequences of its extinction. Publicación Electrónica de la Asociación Paleontológica Argentina 23, 317–330 (2023).

10

E. C. Fricke, A. Ordonez, H. S. Rogers, J.-C. Svenning, The effects of defaunation on plants’ capacity to track climate change. Science 375, 210–214 (2022).

11

C. P. Hedberg, S. K. Lyons, F. A. Smith, The hidden legacy of megafaunal extinction: Loss of functional diversity and resilience over the Late Quaternary at Hall’s Cave. Glob. Ecol. Biogeogr. 31, 294–307 (2022).

12

A. B. Shupinski, P. J. Wagner, F. A. Smith, S. K. Lyons, Unique functional diversity during early Cenozoic mammal radiation of North America. Proc. Biol. Sci. 291, 20240778 (2024).

13

J.-C. Svenning, R. T. Lemoine, J. Bergman, R. Buitenwerf, E. Le Roux, E. Lundgren, N. Mungi, R. Ø. Pedersen, The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene. Camb. Prism. Extinct. 2, e5 (2024).

14

F. A. Smith, A. G. Boyer, J. H. Brown, D. P. Costa, T. Dayan, S. K. M. Ernest, A. R. Evans, M. Fortelius, J. L. Gittleman, M. J. Hamilton, L. E. Harding, K. Lintulaakso, S. K. Lyons, C. McCain, J. G. Okie, J. J. Saarinen, R. M. Sibly, P. R. Stephens, J. Theodor, M. D. Uhen, The evolution of maximum body size of terrestrial mammals. Science 330, 1216–1219 (2010).

15

J. Baker, A. Meade, M. Pagel, C. Venditti, Adaptive evolution toward larger size in mammals. Proc. Natl. Acad. Sci. U.S.A. 112, 5093–5098 (2015).

16

O. Sanisidro, M. C. Mihlbachler, J. L. Cantalapiedra, A macroevolutionary pathway to megaherbivory. Science 380, 616–618 (2023).

17

N. Cooper, A. Purvis, Body size evolution in mammals: Complexity in tempo and mode. Am. Nat. 175, 727–738 (2010).

18

J. T. Faith, J. Rowan, A. Du, W. A. Barr, The uncertain case for human-driven extinctions prior to Homo sapiens. Quat. Res. 96, 88–104 (2020).

19

J. L. Cantalapiedra, Ó. Sanisidro, H. Zhang, M. T. Alberdi, J. L. Prado, F. Blanco, J. Saarinen, The rise and fall of proboscidean ecological diversity. Nat. Ecol. Evol. 5, 1266–1272 (2021).

20

N. Toledo, M. S. Bargo, S. F. Vizcaíno, G. De Iuliis, F. Pujos, Evolution of body size in anteaters and sloths (Xenarthra, Pilosa): Phylogeny, metabolism, diet and substrate preferences. Earth Environ. Sci. Trans. R. Soc. Edinb. 106, 289–301 (2017).

21

S. Raj Pant, A. Goswami, J. A. Finarelli, Complex body size trends in the evolution of sloths (Xenarthra: Pilosa). BMC Evol. Biol. 14, 184 (2014).

22

J. V. Tejada, P.-O. Antoine, P. Münch, G. Billet, L. Hautier, F. Delsuc, F. L. Condamine, Bayesian total-evidence dating revisits sloth phylogeny and biogeography: A cautionary tale on morphological clock analyses. Syst. Biol. 73, 125–139 (2024).

23

F. Delsuc, M. Kuch, G. C. Gibb, E. Karpinski, D. Hackenberger, P. Szpak, J. G. Martínez, J. I. Mead, H. G. McDonald, R. D. E. MacPhee, G. Billet, L. Hautier, H. N. Poinar, Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. Curr. Biol. 29, 2031–2042.e6 (2019).

24

S. Presslee, G. J. Slater, F. Pujos, A. M. Forasiepi, R. Fischer, K. Molloy, M. Mackie, J. V. Olsen, A. Kramarz, M. Taglioretti, F. Scaglia, M. Lezcano, J. L. Lanata, J. Southon, R. Feranec, J. Bloch, A. Hajduk, F. M. Martin, R. Salas Gismondi, M. Reguero, C. de Muizon, A. Greenwood, B. T. Chait, K. Penkman, M. Collins, R. D. E. MacPhee, Palaeoproteomics resolves sloth relationships. Nat. Ecol. Evol. 3, 1121–1130 (2019).

25

D. M. Casali, A. Boscaini, T. J. Gaudin, F. A. Perini, Reassessing the phylogeny and divergence times of sloths (Mammalia: Pilosa: Folivora), exploring alternative morphological partitioning and dating models. Zool. J. Linn. Soc. 196, 1505–1551 (2022).

26

Materials and methods are available as supplementary materials.

27

J. D. Carrillo, S. Faurby, D. Silvestro, A. Zizka, C. Jaramillo, C. D. Bacon, A. Antonelli, Disproportionate extinction of South American mammals drove the asymmetry of the Great American Biotic Interchange. Proc. Natl. Acad. Sci. U.S.A. 117, 26281–26287 (2020).

28

D. Bustos, J. Jakeway, T. M. Urban, V. T. Holliday, B. Fenerty, D. A. Raichlen, M. Budka, S. C. Reynolds, B. D. Allen, D. W. Love, V. L. Santucci, D. Odess, P. Willey, H. G. McDonald, M. R. Bennett, Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America. Sci. Adv. 4, eaar7621 (2018).

29

D. M. Casali, A. Boscaini, T. J. Gaudin, F. A. Perini, Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora). Palaeontology 66, e12639 (2023).

30

H. Tejero-Cicuéndez, I. Menéndez, A. Talavera, G. Mochales-Riaño, B. Burriel-Carranza, M. Simó-Riudalbas, S. Carranza, D. C. Adams, Evolution along allometric lines of least resistance: Morphological differentiation in Pristurus geckos. Evolution 77, 2547–2560 (2023).

31

R. B. Trayler, M. J. Kohn, M. S. Bargo, J. I. Cuitiño, R. F. Kay, C. A. E. Strömberg, S. F. Vizcaíno, Patagonian aridification at the onset of the Mid-Miocene Climatic Optimum. Paleoceanography and Paleoclimatology 35, e2020PA003956 (2020).

32

L. Palazzesi, V. Barreda, Fossil pollen records reveal a late rise of open-habitat ecosystems in Patagonia. Nat. Commun. 3, 1294 (2012).

33

L. Varela, P. S. Tambusso, H. G. McDonald, R. A. Fariña, Phylogeny, macroevolutionary trends and historical biogeography of sloths: Insights from a Bayesian morphological clock analysis. Syst. Biol. 68, 204–218 (2019).

34

M. Domínguez-Rodrigo, E. Baquedano, L. Varela, P. S. Tambusso, M. J. Melián, R. A. Fariña, Deep classification of cut-marks on bones from Arroyo del Vizcaíno (Uruguay). Proc. Biol. Sci. 288, 20210711 (2021).

35

T. R. Pansani, M. A. T. Dantas, L. Asevedo, A. Cherkinsky, D. Vialou, Á. V. Vialou, M. L. A. F. Pacheco, Radiocarbon dating and isotopic palaeoecology of Glossotherium phoenesis from the Late Pleistocene of the Santa Elina rock shelter, Central Brazil. Journal of Quaternary Science, jqs.3553 (2023).

36

D. W. Steadman, P. S. Martin, R. D. E. MacPhee, A. J. T. Jull, H. G. McDonald, C. A. Woods, M. Iturralde-Vinent, G. W. L. Hodgins, Asynchronous extinction of late Quaternary sloths on continents and islands. Proc. Natl. Acad. Sci. U.S.A. 102, 11763–11768 (2005).

37

S. P. Horn, K. H. Orvis, L. M. Kennedy, G. M. Clark, Prehistoric fires in the highlands of the Dominican Republic: Evidence from charcoal in soils and sediments. Caribb. J. Sci. 36, 10–18 (2000).

38

N. Kar, C. N. Garzione, C. Jaramillo, T. Shanahan, V. Carlotto, A. Pullen, F. Moreno, V. Anderson, E. Moreno, J. Eiler, Rapid regional surface uplift of the northern Altiplano plateau revealed by multiproxy paleoclimate reconstruction. Earth Planet. Sci. Lett. 447, 33–47 (2016).

39

C. N. Garzione, G. D. Hoke, J. C. Libarkin, S. Withers, B. MacFadden, J. Eiler, P. Ghosh, A. Mulch, Rise of the Andes. Science 320, 1304–1307 (2008).

40

C. Hoorn, F. P. Wesselingh, H. ter Steege, M. A. Bermudez, A. Mora, J. Sevink, I. Sanmartín, A. Sanchez-Meseguer, C. L. Anderson, J. P. Figueiredo, C. Jaramillo, D. Riff, F. R. Negri, H. Hooghiemstra, J. Lundberg, T. Stadler, T. Särkinen, A. Antonelli, Amazonia through time: Andean uplift, climate change, landscape evolution, and biodiversity. Science 330, 927–931 (2010).

41

B. J. Shockey, F. Anaya, Grazing in a new Late Oligocene mylodontid sloth and a mylodontid radiation as a component of the Eocene-Oligocene faunal turnover and the early spread of grasslands/savannas in South America. J. Mamm. Evol. 18, 101–115 (2011).

42

J. A. Sheridan, D. Bickford, Shrinking body size as an ecological response to climate change. Nat. Clim. Chang. 1, 401–406 (2011).

43

J. L. Gardner, A. Peters, M. R. Kearney, L. Joseph, R. Heinsohn, Declining body size: A third universal response to warming?. Trends Ecol. Evol. 26, 285–291 (2011).

44

S. J. Gould, Ontogeny and Phylogeny (Belknap Press of Harvard Univ. Press, 1977).

45

L. Varela, P. S. Tambusso, J. M. Pérez Zerpa, R. K. McAfee, R. A. Fariña, R. A. Fariña, 3D finite element analysis and geometric morphometrics of sloths (Xenarthra, Folivora) mandibles show insights on the dietary specializations of fossil taxa. J. S. Am. Earth Sci. 128, 104445 (2023).

46

S. F. Vizcaíno, M. Zárate, M. S. Bargo, A. Dondas, Pleistocene burrows in the Mar del Plata area (Argentina) and their probable builders. Acta Palaeontol. Pol. 46, 289–301 (2001).

47

L. Prates, S. I. Perez, Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population. Nat. Commun. 12, 2175 (2021).

48

G. G. Politis, P. G. Messineo, T. W. Stafford Jr., E. L. Lindsey, Campo Laborde: A Late Pleistocene giant ground sloth kill and butchering site in the Pampas. Sci. Adv. 5, eaau4546 (2019).

49

F. A. Smith, R. E. Elliott Smith, S. K. Lyons, J. L. Payne, Body size downgrading of mammals over the late Quaternary. Science 360, 310–313 (2018).

50

T. I. Grand, in The Ecology of Arboreal Folivores, G. G. Montgomery, Ed. (Smithsonian Institution Press, 1978), pp. 231–241.

51

N. Toledo, G. H. Cassini, S. F. Vizcaino, M. S. Bargo, Mass estimation of Santacrucian sloths from the Early Miocene Santa Cruz Formation of Patagonia, ArgentinaActa Palaeontol. Pol. 59, 267–280 (2014).

52

K. M. Scott, in Body Size in Mammalian Paleobiology: Estimation and Biological Implications, J. Damuth, B. J. MacFadden, Eds. (Cambridge University Press, 1990), pp. 301–335.

53

R. A. Fariña, S. F. Vizcaíno, M. S. Bargo, Body mass estimations in Lujanian (Late Pleistocene - Early Holocene of South America) mammal megafaunaMastozool. Neotrop. 5, 87–108 (1998).

54

R Core Team, R: The R Project for Statistical Computing (R Foundation for Statistical Computing, 2017); www.R-project.org/

55

56

J. Lemon, Plotrix: A package in the red light district of RR News 6, 8–12 (2006).

57

F. H. D. S. Barbosa, L. Alves-Silva, A. Liparini, K. D. O. Porpino, Reviewing the body size of some extinct Brazilian Quaternary XenarthransJournal of Quaternary Science, jqs.3560 (2023).

58

A. D. Rincón, A. Solórzano, H. G. McDonald, M. N. Flores, Baraguatherium takumara, gen. et sp. nov., the earliest mylodontoid sloth (Early Miocene) from northern South AmericaJ. Mamm. Evol. 24, 179–191 (2017).

59

A. D. Rincón, H. G. McDonald, A. Solórzano, M. N. Flores, D. Ruiz-Ramoni, A new enigmatic Late Miocene mylodontoid sloth from northern South AmericaR. Soc. Open Sci. 2, 140256 (2015).

60

F. R. Miranda, G. S. T. Garbino, F. A. Machado, F. A. Perini, F. R. Santos, D. M. Casali, Taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), Pilosa, Bradypodidae, with revalidation of Bradypus crinitus Gray, 1850. J. Mammal. 104, 86–103 (2023).

61

P. J. Adam, Choloepus didactylus. Mamm. Species 621, 1–8 (1999).

62

V. Hayssen, Bradypus pygmaeus (Pilosa: Bradypodidae). Mamm. Species 812, 1–4 (2008).

63

V. Hayssen, Bradypus torquatus (Pilosa: Bradypodidae). Mamm. Species 829, 1–5 (2009).

64

V. Hayssen, Bradypus variegatus (Pilosa: Bradypodidae). Mamm. Species 42, 19–32 (2010).

65

V. Hayssen, Bradypus tridactylus (Pilosa: Bradypodidae). Mamm. Species 839, 1–9 (2009).

66

V. Hayssen, Choloepus hoffmanni (Pilosa: Megalonychidae). Mamm. Species 43, 37–55 (2011).

67

A. Boscaini, F. Pujos, T. J. Gaudin, A reappraisal of the phylogeny of Mylodontidae (Mammalia, Xenarthra) and the divergence of mylodontine and lestodontine sloths. Zool. Scr. 48, 691–710 (2019).

68

F. Ronquist, M. Teslenko, P. van der Mark, D. L. Ayres, A. Darling, S. Höhna, B. Larget, L. Liu, M. A. Suchard, J. P. Huelsenbeck, MrBayes 3.2: Efficient Bayesian phylogenetic inference and model choice across a large model space. Syst. Biol. 61, 539–542 (2012).

69

A. Boscaini, N. Toledo, L. M. Pérez, M. L. Taglioretti, R. K. Mcafee, New well-preserved materials of Glossotherium chapadmalense (Xenarthra, Mylodontidae) from the Pliocene of Argentina shed light on the origin and evolution of the genus. J. Vertebr. Paleontol. 42, e2128688 (2022).

70

T. J. Gaudin, A. Boscaini, B. Mamani Quispe, R. Andrade Flores, M. Fernández-Monescillo, L. Marivaux, P.-O. Antoine, P. Münch, F. Pujos, Recognition of a new nothrotheriid genus (Mammalia, Folivora) from the early late Miocene of Achiri (Bolivia) and the taxonomic status of the genus Xyophorus. Hist. Biol. 35, 1041–1051 (2023).

71

P. O. Lewis, A likelihood approach to estimating phylogeny from discrete morphological character data. Syst. Biol. 50, 913–925 (2001).

72

L. B. Harrison, H. C. E. Larsson, Among-character rate variation distributions in phylogenetic analysis of discrete morphological characters. Syst. Biol. 64, 307–324 (2015).

73

G. C. Gibb, F. L. Condamine, M. Kuch, J. Enk, N. Moraes-Barros, M. Superina, H. N. Poinar, F. Delsuc, Shotgun mitogenomics provides a reference phylogenetic framework and timescale for living xenarthrans. Mol. Biol. Evol. 33, 621–642 (2016).

74

T. A. Heath, J. P. Huelsenbeck, T. Stadler, The fossilized birth-death process for coherent calibration of divergence-time estimates. Proc. Natl. Acad. Sci. U.S.A. 111, E2957–E2966 (2014).

75

C. Zhang, T. Stadler, S. Klopfstein, T. A. Heath, F. Ronquist, Total-evidence dating under the fossilized birth–death process. Syst. Biol. 65, 228–249 (2016).

76

A. Rambaut, A. J. Drummond, D. Xie, G. Baele, M. A. Suchard, Posterior summarization in Bayesian phylogenetics using Tracer 1.7. Syst. Biol. 67, 901–904 (2018).

77

S. P. Blomberg, T. Garland Jr., A. R. Ives, Testing for phylogenetic signal in comparative data: Behavioral traits are more labile. Evolution 57, 717–745 (2003).

78

L. J. Revell, phytools 2.0: An updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ 12, e16505 (2024).

79

T. Münkemüller, S. Lavergne, B. Bzeznik, S. Dray, T. Jombart, K. Schiffers, W. Thuiller, How to measure and test phylogenetic signal. Methods Ecol. Evol. 3, 743–756 (2012).

80

E. Paradis, J. Claude, K. Strimmer, APE: Analyses of Phylogenetics and Evolution in R language. Bioinformatics 20, 289–290 (2004).

81

H. Akaike, A new look at the statistical model identification. IEEE Trans. Automat. Contr. 19, 716–723 (1974).

82

C. M. Hurvich, C.-L. Tsai, Regression and time series model selection in small samples. Biometrika 76, 297–307 (1989).

83

L. Harmon, Phylogenetic Comparative Methods: Learning from Trees (CreateSpace, 2019).

84

85

J. Felsenstein, Phylogenies and the comparative method. Am. Nat. 125, 1–15 (1985).

86

T. F. Hansen, Stabilizing selection and the comparative analysis of adaptation. Evolution 51, 1341–1351 (1997).

87

J. M. Beaulieu, D. C. Jhwueng, C. Boettiger, B. C. O’Meara, Modeling stabilizing selection: Expanding the Ornstein-Uhlenbeck model of adaptive evolution. Evolution 66, 2369–2383 (2012).

88

L. J. Harmon, J. B. Losos, T. Jonathan Davies, R. G. Gillespie, J. L. Gittleman, W. Bryan Jennings, K. H. Kozak, M. A. McPeek, F. Moreno-Roark, T. J. Near, A. Purvis, R. E. Ricklefs, D. Schluter, J. A. Schulte Ii, O. Seehausen, B. L. Sidlauskas, O. Torres-Carvajal, J. T. Weir, A. Ø. Mooers, Early bursts of body size and shape evolution are rare in comparative data. Evolution 64, 2385–2396 (2010).

89

M. Pagel, Inferring the historical patterns of biological evolution. Nature 401, 877–884 (1999).

90

N. Eldredge, S. J. Gould, in Models in Paleobiology, T. J. M. Schopf, Ed. (Freeman, Cooper & Co, 1972); vol. 82, pp. 82–115.

91

T. Westerhold, N. Marwan, A. J. Drury, D. Liebrand, C. Agnini, E. Anagnostou, J. S. K. Barnet, S. M. Bohaty, D. De Vleeschouwer, F. Florindo, T. Frederichs, D. A. Hodell, A. E. Holbourn, D. Kroon, V. Lauretano, K. Littler, L. J. Lourens, M. Lyle, H. Pälike, U. Röhl, J. Tian, R. H. Wilkens, P. A. Wilson, J. C. Zachos, An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science 369, 1383–1387 (2020).

92

A. O’Dea, H. A. Lessios, A. G. Coates, R. I. Eytan, S. A. Restrepo-Moreno, A. L. Cione, L. S. Collins, A. de Queiroz, D. W. Farris, R. D. Norris, R. F. Stallard, M. O. Woodburne, O. Aguilera, M.-P. Aubry, W. A. Berggren, A. F. Budd, M. A. Cozzuol, S. E. Coppard, H. Duque-Caro, S. Finnegan, G. M. Gasparini, E. L. Grossman, K. G. Johnson, L. D. Keigwin, N. Knowlton, E. G. Leigh, J. S. Leonard-Pingel, P. B. Marko, N. D. Pyenson, P. G. Rachello-Dolmen, E. Soibelzon, L. Soibelzon, J. A. Todd, G. J. Vermeij, J. B. C. Jackson, Formation of the Isthmus of Panama. Sci. Adv. 2, e1600883 (2016).

93

M. Del Papa, M. De Los Reyes, D. G. Poiré, N. Rascovan, G. Jofré, M. Delgado, Anthropic cut marks in extinct megafauna bones from the Pampean region (Argentina) at the last glacial maximum. PLOS ONE 19, e0304956 (2024).

94

T. J. Braje, J. M. Erlandson, T. C. Rick, L. Davis, T. Dillehay, D. W. Fedje, D. Froese, A. Gusick, Q. Mackie, D. McLaren, B. Pitblado, J. Raff, L. Reeder-Myers, M. R. Waters, Fladmark + 40: What have we learned about a potential Pacific Coast peopling of the Americas?. Am. Antiq. 85, 1–21 (2019).

95

J. Clavel, G. Escarguel, G. Merceron, mvMORPH: An R package for fitting multivariate evolutionary models to morphometric data. Methods Ecol. Evol. 6, 1311–1319 (2015).

96

L. J. Harmon, J. T. Weir, C. D. Brock, R. E. Glor, W. Challenger, GEIGER: Investigating evolutionary radiations. Bioinformatics 24, 129–131 (2008).

97

S. Holm, A simple sequentially rejective multiple test procedure. Scand. J. Stat. Theory Appl. 6, 65–70 (1979).

98

T. Guillerme, N. Cooper, S. L. Brusatte, K. E. Davis, A. L. Jackson, S. Gerber, A. Goswami, K. Healy, M. J. Hopkins, M. E. H. Jones, G. T. Lloyd, J. E. O’Reilly, A. Pate, M. N. Puttick, E. J. Rayfield, E. E. Saupe, E. Sherratt, G. J. Slater, V. Weisbecker, G. H. Thomas, P. C. J. Donoghue, Disparities in the analysis of morphological disparity. Biol. Lett. 16, 20200199 (2020).

99

T. Guillerme, dispRity: A modular R package for measuring disparity. Methods Ecol. Evol. 9, 1755–1763 (2018).

100

B. S. Martin, G. S. Bradburd, L. J. Harmon, M. G. Weber, Modeling the evolution of rates of continuous trait evolution. Syst. Biol. 72, 590–605 (2023).

101

M. Sakamoto, C. Venditti, Phylogenetic non-independence in rates of trait evolution. Biol. Lett. 14, 20180502 (2018).

102

G. Schwarz, Estimating the dimension of a model. Ann. Stat. 6, 461–464 (1978).

103

104

J. Zachos, M. Pagani, L. Sloan, E. Thomas, K. Billups, Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292, 686–693 (2001).

105

T. Guillerme, N. Cooper, Time for a rethink: Time sub-sampling methods in disparity-through-time analyses. Palaeontology 61, 481–493 (2018).

106

T. M. Mattila, F. Bokma, Extant mammal body masses suggest punctuated equilibrium. Proc. Biol. Sci. 275, 2195–2199 (2008).

107

108

L. A. Jones, W. Gearty, B. J. Allen, K. Eichenseer, C. D. Dean, S. Galván, M. Kouvari, P. L. Godoy, C. S. C. Nicholl, L. Buffan, E. M. Dillon, J. T. Flannery-Sutherland, A. A. Chiarenza, palaeoverse: A community-driven R package to support palaeobiological analysis. Methods Ecol. Evol. 14, 2205–2215 (2023).

109

110

111

H. Wickham, ggplot2: Elegant Graphics for Data Analysis (Springer, Cham, ed. 3rd, 2016).

112

113

G. Yu, D. K. Smith, H. Zhu, Y. Guan, T. T.-Y. Lam, ggtree: An R package for visualization and annotation of phylogenetic trees with their covariates and other associated data. Methods Ecol. Evol. 8, 28–36 (2017).

114

115

116

117

118

119

H. Wickham, Reshaping data with the reshape package. J. Stat. Softw. 21, 1–20 (2007).

120

P. Schauberger, A. Walker, L. Braglia, J. Sturm, J. M. Garbuszus, J. M. Barbone, D. Zimmermann, R. Kainhofer, openxlsx: read, write and edit xlsx files, R package version 4.2.7.1 (2024); https://cran.r-project.org/web/packages/openxlsx/index.html.

121

T. J. Gaudin, The ear region of Edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra). J. Vertebr. Paleontol. 15, 672–705 (1995).

122

T. J. Gaudin, Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): The craniodental evidence. Zool. J. Linn. Soc. 140, 255–305 (2004).

123

E. Amson, C. de Muizon, T. J. Gaudin, A reappraisal of the phylogeny of the Megatheria (Mammalia: Tardigrada), with an emphasis on the relationships of the Thalassocninae, the marine sloths. Zool. J. Linn. Soc. 179, 217–236 (2017).

124

A. J. Stuart, Mammalian extinctions in the late Pleistocene of northern Eurasia and North America. Biol. Rev. Camb. Philos. Soc. 66, 453–562 (1991).

125

J. L. White, Indicators of locomotor habits in xenarthrans: Evidence for locomotor heterogeneity among fossil sloths. J. Vertebr. Paleontol. 13, 230–242 (1993).

126

R. M. Nowak, Walker’s Mammals of the World (Johns Hopkins Univ. Press, 1999).

127

M. S. Bargo, S. F. Vizcaíno, F. M. Archuby, R. E. Blanco, Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) Mylodontid Ground Sloths (Mammalia: Xenarthra). J. Vertebr. Paleontol. 20, 601–610 (2000).

128

D. A. Croft, “Archaeohyracidae (Mammalia: Notoungulata) from the Tinguiririca Fauna, Central Chile, and the Evolution and Paleoecology of South American Mammalian Herbivores,” thesis, University of Chicago, Department of Organismal Biology and Anatomy (2000).

129

H. G. McDonald, Paleoecology of extinct xenarthrans and the great biotic interchange. Bulletin of the Florida Museum of Natural History 45, 319–340 (2005).

130

S. F. Vizcaíno, M. S. Bargo, G. H. Cassini, Dental occlusal surface area in relation to body mass, food habits and other biological features in fossil xenarthrans. Ameghiniana 43, 11–26 (2006).

131

S. De Esteban-Trivigno, M. Mendoza, M. De Renzi, Body mass estimation in xenarthra: A predictive equation suitable for all quadrupedal terrestrial placentals?. J. Morphol. 269, 1276–1293 (2008).

132

G. De Iuliis, G. H. Ré, S. F. Vizcaíno, The Toro Negro Megatheriinae, (Mammalia, Xenarthra); a new species of Pyramiodontherium and a review of Plesiomegatherium. J. Vertebr. Paleontol. 24, 214–227 (2004).

133

S. E. Fields, The ground sloth Megalonyx (Xenarthra: Megalonychidae) from the Pleistocene (Late Irvingtonian) Camelot Local Fauna, Dorchester County, South Carolina. Trans. Am Philos. Soc. 100, 1–76 (2010).

134

H. G. McDonald., Evolution of the pedolateral foot in ground sloths: Patterns of change in the astragalus. J. Mamm. Evol. 19, 209–215 (2012).

135

H. G. McDonald, Yukon to the Yucatan: Habitat partitioning in North American Late Pleistocene ground sloths (Xenarthra, Pilosa). Journal of Palaeosciences 70, 237–252 (2021).

136

M. A. T. Dantas, Estimating the body mass of the Late Pleistocene megafauna from the South America Intertropical Region and a new regression to estimate the body mass of extinct xenarthrans. J. S. Am. Earth Sci. 119, 103900 (2022).

137

M. A. T. Dantas, S. C. Campbell, H. G. McDonald, Paleoecological inferences about the Late Quaternary giant sloths. J. Mamm. Evol. 30, 891–905 (2023).

138

H. G. McDonald, A tale of two continents (and a few islands): Ecology and distribution of Late Pleistocene sloths. Land 12, 1192 (2023).

139

A. M. A. Santos, H. G. McDonald, M. A. T. Dantas, Inferences of the ecological habits of extinct giant sloths from the Brazilian Intertropical Region. J. Quaternary Sci. 39, 1168–1174 (2023).

140

N. Toledo, M. S. Bargo, S. F. Vizcaíno, Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra, Folivora) of Patagonia. The Anatomical Record 298, 842–864 (2015).

141

N. Toledo, M. S. Bargo, G. H. Cassini, S. F. Vizcaíno, . The forelimb of Early Miocene sloths (Mammalia, Xenarthra, Folivora): Morphometrics and functional implications for substrate preferences. J. Mamm. Evol. 19, 185–198 (2012).

142

G. De Iuliis, F. Pujos, C. Cartelle, A new ground sloth (Mammalia: Xenarthra) from the Quaternary of Brazil. C. R. Palevol 8, 705–715 (2009).

143

F. Pujos, G. De Iuliis, B. Mamani Quispe, S. Adnet, R. Andrade Flores, G. Billet, M. Fernandez-Monescillo, L. Marivaux, P. Münch, M. B. Prámparo, P.-O. Antoine, A new nothrotheriid xenarthran from the early Pliocene of Pomata-Ayte (Bolivia): New insights into the caniniform-molariform transition in sloths. Zool. J. Linn. Soc. 178, 679–712 (2016).

144

C. Cartelle, J. S. Fonseca, Contribuição ao melhor conhecimento da pequena preguiça terrícola Nothrotherium maquinense (Lund), Lydekker, 1889. Lundiana 2, 127–181 (1983).

145

F. Pujos, M. R. Ciancio, A. M. Forasiepi, M. Pujos, A. M. Candela, B. Vera, M. A. Reguero, A. M. Combina, E. Cerdeño, The late Oligocene xenarthran fauna of Quebrada Fiera (Mendoza, Argentina) and its implications for sloth origins and the diversity of Palaeogene cingulates. Pap. Palaeontol. 7, 1613–1656 (2021).

146

J. L. White, in Vertebrate paleontology in the neotropics: The Miocene fauna of La Venta (Smithsonian Institution Press, 1997), pp. 246–264.

147

A. Boscaini, N. Toledo, B. Mamani Quispe, R. Andrade Flores, M. Fernández-Monescillo, L. Marivaux, P.-O. Antoine, P. Münch, T. J. Gaudin, F. Pujos, Postcranial anatomy of the extinct terrestrial sloth Simomylodon uccasamamensis (Xenarthra, Mylodontidae) from the Pliocene of the Bolivian Altiplano, and its evolutionary implications. Pap. Palaeontol. 7, 1557–1583 (2021).

148

E. Amson, C. de Muizon, M. Laurin, C. Argot, V. de Buffrénil, Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru. Proc. Biol. Sci. 281, 20140192 (2014).

149

N. A. Resar, J. L. Green, R. K. McAfee, Reconstructing paleodiet in ground sloths (Mammalia, Xenarthra) using dental microwear analysis. Kirtlandia 58, 61–72 (2013).

150

J. Saarinen, A. Karme, Tooth wear and diets of extant and fossil xenarthrans (Mammalia, Xenarthra)–applying a new mesowear approach. Palaeogeogr. Palaeoclimatol. Palaeoecol. 476, 42–54 (2017).

151

M. S. Bargo, N. Toledo, S. F. Vizcaíno, Muzzle of South American Pleistocene ground sloths (Xenarthra, Tardigrada). J. Morphol. 267, 248–263 (2006).

152

V. L. Naples, R. K. McAfee, Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa). F1000 Res. 3, 86 (2014).

153

R. K. McAfee, Feeding mechanics and dietary implications in the fossil sloth Neocnus (Mammalia: Xenarthra: Megalonychidae) from Haiti. J. Morphol. 272, 1204–1216 (2011).

154

D. C. Kalthoff, J. L. Green, Feeding ecology in Oligocene mylodontoid sloths (Mammalia, Xenarthra) as revealed by orthodentine microwear analysis. J. Mamm. Evol. 25, 551–564 (2018).

155

M. S. Bargo, S. F. Vizcaíno, R. F. Kay, Predominance of orthal masticatory movements in the early Miocene Eucholaeops (Mammalia, Xenarthra, Tardigrada, Megalonychidae) and other megatherioid sloths. J. Vertebr. Paleontol. 29, 870–880 (2009).