1080


Journal of Paleontology 91(5):1069–1082


previously suspected. This reflects the general paucity of Cenozoic fossil sites from the tropical lower latitudes in North America and that the majority of our knowledge of the diversity of taxa that participated in the GABI and the timing of their dispersal into North America has been based on faunas from higher latitudes. The presence of these sloths raises interesting questions in terms of the evolutionary history of the mega- lonychid sloths and whether their appearance in North America reflects multiple separate dispersal events or a smaller number of dispersals with the subsequent evolution of these taxa occurring in the tropical portions of North America. The presence of these taxa only in North America and their absence in South America suggest this may be the case, but alternatively could simply reflect that, as in North America, there are fewer sites from the late Cenozoic in the tropical parts of northern South America. These questions cannot be resolved until additional fieldwork in the adjoining tropical regions of South and North America provides us with a more robust fossil record.


Acknowledgments


Our thanks to the Centro de Geociencias of the Universidad Nacional Autónoma de México for the support and logistics to carry out the fieldwork and preparation of the fossil material. These were possible with the economic support of the project PAPIIT IN102817. We thank W.E. Miller of Brigham Young University for his participation during the research on the sedimentary basins of central Mexico, B.Kowallis fromBYUfor description of the geology and stratigraphy and radiometric ages of the Tecolotlán Basin.We thank J. Silva Corona for the figures and photographs in this work, H. Troncoso for the preparation of the fossils collected, C. Luis Espinosa for his criticism of part of the manuscript, and C. Ortega (LA-ICPMS), Centro de Geociencias for the second analysis of ash. The Center for Field Research, and especially EarthWatch volunteers, are thanked for their support of the Fossils of the SierraMadre project, and their invaluable help collecting fossils during this project. We thank P. Holroyd, UCMP, for providing pictures of the Pliometanastes from the Siphon Canal Locality and L. Fowler for providing the measurements of this specimen. S. Bargo, D. Brandoni, and S. Hirschfeld generously provided images of specimens from their publications. We thank our reviewers, D. Croft and G. DeIuliis, for their comments, which improved the quality of the paper.


References


Ameghino, F., 1885,Nuevos restos demamíferos fósiles Oligocenos recogidos por el Profesor Pedro Scalabrini y pertenecientes al Museo Provincial de la ciudad de Paraná:Boletín de la Academia Nacional de Ciencias de Córdoba, v. 8, p. 5–207.


Ameghino, F., 1887, Enumeracion sistematica de las especies de mamiferos fosiles coleccionados por Carlos Ameghino en los terrenos eocenos de la Patagonia: Boletín del Museo de La Plata, v. 1, p. 1–26.


Bargo, M.S, Toledo, N., and Vizcaíno., S.F., 2012. Paleobiology of the Santacrucian sloths and anteaters (Xenarthra, Pilosa), in Vizcaíno, S.A., Kay, R.F., and Bargo, M.S., eds., Early Miocene Paleobiology in Patagonia: Cambridge, Cambridge University Press, p. 216–242.


Brandoni, D., 2010, On the systematics of Ortotherium Ameghino (Xenarthra, Tardigrada Megalonychidae) from the ‘Conglomerado Osíferó’ (Late Miocene) of Argentina: Journal of Vertebrate Paleontology, v. 30, p. 975–980.


Brandoni, D., 2014, A new genus of Megalonychidae (Mammalia, Xenarthra) from the late Miocene of Argentina: Revista Brasileira de Paleontologia, v. 17, p. 33–42.


Brown, B., 1912, Brachyostracon, a new genus of glyptodonts from Mexico: American Museum of Natural History Bulletin, v. 31, p. 167–177.


Carlini, A.A., and Scillato-Yané, G.J., 2004, The oldest Megalonychidae (Xenarthra: Tardigrada); phylogenetic relationships and an emended diagnosis of the family: Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, v. 233, p. 423–443.


Carranza, O., and Miller, W.E., 1980, The earliest capybara record in North America. Geological Society of America Abstracts with Programs, v. 12, p. 399.


Carranza-Castañeda, O., 1991, Vertebrados Fósiles del Terciario del Estado Hidalgo, in Rubinovish-Kogan, R., and Carreño, A.L., eds., Convencion sobre la Evolucion Geologica de Mexico y I Congreso Mexicano de Mineralogia, Memoria: Universidad Nacional Autonoma de Mexico, Intituto de Geologia; Universidad Autonoma de Hidalgo, Instituto de Investigaciones de Ciencias de la Tierra; and Sociedad Mexicana de Mineralogia; Secretaria de Educacion Publica, p. 23.


Carranza-Castañeda, O., 2016, Roedores caviomorfos (Rodentia Hydrochoeridae) del Blancano temprano tardío—Irvingtoniano de los estados de Guanajuato, Jalisco y Sonora, México: relación con Phugatherium dichroplax: Revista Mexicana de Ciencias Geológicas, v. 33, p. 297–315.


Carranza-Castañeda, O., and Miller, W.E., 1988, Roedores caviomorfos de la Mesa Central de México, Blancano temprano (Plioceno tardío) de la fauna local Rancho Viejo, Guanajuato, México: Universidad Nacional Autónoma de México, Instituto de Geología, Revista, v. 7, p. 182–199.


Carranza-Castañeda, O., and Miller, W.E., 2004, Late Tertiary terrestrial mammals from Central Mexico and their relationship to South American immigrants: Revista Brasileira de Paleontologia, v. 7, p. 249–261.


Carranza-Castañeda, O., Aranda-Gómez, J.J., Wang, X., and Iriondo, A., 2013, The early–late Hemphillian (Hh2) faunal assemblage from Juchipila Basin, State of Zacatecas, Mexico, and its biochronological correlation with other Hemphillian faunas in Central Mexico: Natural History Museum of Los Angeles County, Contributions in Science, v. 521, p. 13–49.


Carrillo, J.D., Forasiepi, A., Jaramillo, C., and Sánchez-Villagra, M.R., 2015, Neotropical mammal diversity and the Great American Biotic Interchange: spatial and temporal variation in South America’s fossil record: Frontiers in Genetics, v. 5, p. 1–11.


Cartelle, C., De Iuliis, G., and Pujos, F., 2008,Anew species of Megalonychidae (Mammalia, Xenarthra) from the Quaternary of Poço Azul (Bahia, Brazil): Comptes Rendus Palevol, v. 7, p. 335–346.


Cook, H.J., 1922,APliocene fauna from Yuma County, Colorado, with notes on the closely related Snake Creek beds from Nebraska: Proceedings of the Colorado Museum of Natural History, v. 4, p. 3–30.


Cope, E.D., 1878, Descriptions of new extinct vertebrata from the Upper Tertiary and Dakota Formations: Bulletin of the United States Geological and Geographical Survey of the Territories, v. 4, p. 379–396.


Cope, E.D., 1889, The Edentata of North America: American Naturalist, v. 23, p. 657–664.


Cope, E.D., 1892,Acontribution to a knowledge of the fauna of the Blanco beds of Texas: Academy of Natural Sciences Proceedings, v. 44, p. 226–229.


Cope, E.D., 1893, A preliminary report on the vertebrate paleontology of the Llano Estacado: Geological Survey of Texas, Annual Report, 4th, p. 1–36.


Croft, D.A., 2007, The middle Miocene (Laventan) Quebrada Honda fauna, southern Bolivia, and a description of its notoungulates: Palaeontology, v. 5, p. 277–303.


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


De Iuliis, G., Cartelle, C., and Pujos, F., 2016, New Pleistocene remains of megalonychid ground sloths (Xenarthra, Pilosa) from the intertropical Brazilian region: Journal of Paleontology, v. 90, p. 578–587.


Flower, W.H., 1883, On the arrangement of the orders and families of existing Mammalia: Proceedings of the Zoological Society of London, v. 1883, p. 178–186.


Flynn, J.J., Kowallis, B.J., Nuñez, C., Carranza-Castañeda, O., Miller, W.E., Swisher, C.C., and Lindsay, E., 2005, Geochronology of Hemphillian– Blancan aged strata, Guanajuato, Mexico, and implications of the Great American Biotic Interchange: Journal of Geology, v. 113, p. 287–307.


Furlong, E.L., 1941, A new Pliocene antelope from Mexico with remarks on some known antilocaprids: Publication of the Carnegie Institute of Washington, v. 530, p. 25–33.


Gaudin, T.J., 1995, The ear region of edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra): Journal of Vertebrate Paleontology, v. 15, p. 672–705.


Gaudin, T.J., 2004, Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence: Zoological Journal of the Linnaean Society, v. 140, p. 255–305.


Gaudin, T.J., and Croft, D.A., 2015, Paleogene Xenarthra and the evolution of South American mammals: Journal of Mammalogy, v. 96, p. 622–634.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212  |  Page 213  |  Page 214  |  Page 215  |  Page 216  |  Page 217  |  Page 218  |  Page 219  |  Page 220  |  Page 221  |  Page 222  |  Page 223  |  Page 224  |  Page 225  |  Page 226  |  Page 227  |  Page 228  |  Page 229  |  Page 230  |  Page 231  |  Page 232  |  Page 233  |  Page 234  |  Page 235  |  Page 236  |  Page 237  |  Page 238