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Michael O. Woodburne - One of the best experts on this subject based on the ideXlab platform.
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Paleogene Land Mammal Faunas of South America; a Response to Global Climatic Changes and Indigenous Floral Diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, A Iglesias, Alfredo Armando Carlini, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored. The Paleogene floras of Patagonia and Chile show a climatic pattern that approximates that of North America, with an increase in both Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) from the Paleocene into the Early Eocene Climatic Optimum (EECO), although the Paleocene-Eocene Thermal Maximum (PETM) is not recognized in the available data set. Post-EECO temperatures declined in both regions, but more so in the north than the south, which also retained a higher rate of precipitation. The South American Paleogene Mammal faunas developed gradual, but distinct, changes in composition and diversity as the EECO was approached, but actually declined somewhat during its peak, contrary to the record in North America. At about 40 Ma, a post-EECO decline was recovered in both hemispheres, but the South American record achieved its greatest diversity then, rather than at the peak of the EECO as in the north. This post-EECO faunal turnover apparently was a response to the changing conditions when global climate was deteriorating toward the Oligocene. Under the progressively more temperate to seasonally arid conditions in South America, this turnover reflected a major change from the more archaic, and more tropical to subtropical-adapted Mammals, to the beginning of the ultimately modern South American fauna, achieved completely by the Eocene-Oligocene transition. Interestingly, hypsodonty was achieved by South American cursorial Mammals about 15–20 m.y. earlier than in North America. In addition to being composed of essentially different groups of Mammals, those of the South American continent seem to have responded to the climatic changes associated with the ECCO and subsequent conditions in a pattern that was initially comparable to, but subsequently different from, their North American counterparts.
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paleogene Land Mammal faunas of south america a response to global climatic changes and indigenous floral diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, Alfredo Armando Carlini, Ari Iglesias, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored.
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Revised timing of the South American early Paleogene Land Mammal ages
Journal of South American Earth Sciences, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Javier N. Gelfo, María Sol Raigemborn, Matthew T. Heizler, Édison V. OliveiraAbstract:Abstract A new Ar/Ar date on the Las Flores Tuff (Rio Chico Group, Las Flores Fm., central Patagonia, Argentina) yielded an age of 49.512 ± 0.019 Ma. This tuff, which stratigraphically overlies the Mammal-bearing deposits that produced the Las Flores fauna, helps constrain the age of the Itaboraian SALMA [South American Land Mammal Age] to which that fauna is referred. The new data also have implications for the age of succeeding Mammal biochrons, such as the Riochican and “Sapoan” which are revised to being somewhat younger than previously interpreted. Although closer in age than formerly interpreted, they still are biotically distinct. Concomitant evaluations suggest that the Itaboraian SALMA is perhaps more contemporary with the EECO (Early Eocene Climatic Optimum) than previously considered. The Riochican may be interpreted as post-EECO, with its cooler climate consistent in that regard. A recent reconsideration of the chronology of elements of the Salamanca Formation resulted in the downward revision of the ages of the Peligran SALMA and the Carodnia Zone biochrons. These operations, together with our results, reflect a 9 m.y. gap in the late Paleocene and early Eocene Land Mammal record in South America.
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Geochronology of the Upper Alturas Formation, northern California: Implications for the Hemphillian-Blancan North American Land Mammal Age boundary
Palaeontologia Electronica, 2014Co-Authors: Steven R. May, Michael O. Woodburne, Everett H. Lindsay, Andrei M. Sarna-wojcicki, Neil D. Opdyke, Elmira Wan, David B. Wahl, Holly A. OlsonAbstract:Fossil vertebrates from the Alturas Formation in northern California have previously been considered important for defining the age of the boundary between the Hemphillian and Blancan North American Land Mammal Ages. Diatomaceous mudstone of the upper Alturas Formation contain fossil Mammals including the arvicoline rodent Mimomys (Ogmodontomys) sawrockensis that is diagnostic of Blancan faunas. New paleomagnetic and geochemical data from the upper Alturas Formation constrain the age of the first stratigraphic occurrence of M. (O.) sawrockensis at Crowder Flat Road to between 4.5 and 4.6 Ma. This age is approximately 0.2-0.4 Ma younger than previously reported such that the oldest record of Mimomys in North America, south of 55oN, is from Panaca, Nevada, and is constrained geochronologically to be approximately 4.9 Ma. The Hemphillian – Blancan North American Land Mammal Age boundary probably occurs within magnetic polarity Chron C3n.3r at approximately 4.9 Ma.
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The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens
Journal of Mammalian Evolution, 2010Co-Authors: Michael O. WoodburneAbstract:The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian Land Mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies.
Ana Natalia Zimicz - One of the best experts on this subject based on the ideXlab platform.
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Paleogene Land Mammal Faunas of South America; a Response to Global Climatic Changes and Indigenous Floral Diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, A Iglesias, Alfredo Armando Carlini, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored. The Paleogene floras of Patagonia and Chile show a climatic pattern that approximates that of North America, with an increase in both Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) from the Paleocene into the Early Eocene Climatic Optimum (EECO), although the Paleocene-Eocene Thermal Maximum (PETM) is not recognized in the available data set. Post-EECO temperatures declined in both regions, but more so in the north than the south, which also retained a higher rate of precipitation. The South American Paleogene Mammal faunas developed gradual, but distinct, changes in composition and diversity as the EECO was approached, but actually declined somewhat during its peak, contrary to the record in North America. At about 40 Ma, a post-EECO decline was recovered in both hemispheres, but the South American record achieved its greatest diversity then, rather than at the peak of the EECO as in the north. This post-EECO faunal turnover apparently was a response to the changing conditions when global climate was deteriorating toward the Oligocene. Under the progressively more temperate to seasonally arid conditions in South America, this turnover reflected a major change from the more archaic, and more tropical to subtropical-adapted Mammals, to the beginning of the ultimately modern South American fauna, achieved completely by the Eocene-Oligocene transition. Interestingly, hypsodonty was achieved by South American cursorial Mammals about 15–20 m.y. earlier than in North America. In addition to being composed of essentially different groups of Mammals, those of the South American continent seem to have responded to the climatic changes associated with the ECCO and subsequent conditions in a pattern that was initially comparable to, but subsequently different from, their North American counterparts.
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paleogene Land Mammal faunas of south america a response to global climatic changes and indigenous floral diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, Alfredo Armando Carlini, Ari Iglesias, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored.
Eliseu V. Dias - One of the best experts on this subject based on the ideXlab platform.
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A New South American Paleogene Land Mammal Fauna, Guabirotuba Formation (Southern Brazil)
Journal of Mammalian Evolution, 2017Co-Authors: Fernando A. Sedor, Édison V. Oliveira, David D. Silva, Luiz A. Fernandes, Renata F. Cunha, Ana M. Ribeiro, Eliseu V. DiasAbstract:The Paleogene vertebrate-bearing sites of Brazil are restricted to few formations such as Maria Farinha (Late Cretaceous-early Paleocene), Itaboraí (early Eocene), Entre-Córregos (Eocene-Oligocene), and Tremembé (late Oligocene-early Miocene). A new Paleogene fauna is reported from an outcrop of the Guabirotuba Formation located at Curitiba, Paraná State, southern Brazil. The Guabirotuba Formation is a stratigraphic unit of the Curitiba Basin, which belongs to the Cenozoic continental rift system of southeastern Brazil, a predominantly half-graben and horst system. The sedimentary facies indicate a fluvial distributary depositional system associated with floodplain, generated under humid climate conditions alternating with drier periods. This new Paleogene fauna, here named the Guabirotuba Fauna, has invertebrate and vertebrate taxa, including Mammals (Cingulata, Notoungulata, Astrapotheria, and Metatheria). The fossil remains of seven armored xenarthrans are identified, including the description of a new species and genus named Proeocoleophorus carlinii . The Guabirotuba ungulates are assigned to Interatheriidae, Oldfieldthomasiidae, and Astrapotheria. The metatherian Mammals are represented by a sparassodont, a palaeothentoid, and an argyrolagoid. This new Mammalian fauna preliminarily suggests a late middle Eocene age (Barrancan South American Land Mammal Age) for the Guabirotuba Formation.
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A New South American Paleogene Land Mammal Fauna, Guabirotuba Formation (Southern Brazil)
Journal of Mammalian Evolution, 2016Co-Authors: Fernando A. Sedor, Édison V. Oliveira, Luiz A. Fernandes, Renata F. Cunha, Ana M. Ribeiro, D. T. Da Silva, Eliseu V. DiasAbstract:The Paleogene vertebrate-bearing sites of Brazil are restricted to few formations such as Maria Farinha (Late Cretaceous-early Paleocene), Itaborai (early Eocene), Entre-Corregos (Eocene-Oligocene), and Tremembe (late Oligocene-early Miocene). A new Paleogene fauna is reported from an outcrop of the Guabirotuba Formation located at Curitiba, Parana State, southern Brazil. The Guabirotuba Formation is a stratigraphic unit of the Curitiba Basin, which belongs to the Cenozoic continental rift system of southeastern Brazil, a predominantly half-graben and horst system. The sedimentary facies indicate a fluvial distributary depositional system associated with floodplain, generated under humid climate conditions alternating with drier periods. This new Paleogene fauna, here named the Guabirotuba Fauna, has invertebrate and vertebrate taxa, including Mammals (Cingulata, Notoungulata, Astrapotheria, and Metatheria). The fossil remains of seven armored xenarthrans are identified, including the description of a new species and genus named Proeocoleophorus carlinii. The Guabirotuba ungulates are assigned to Interatheriidae, Oldfieldthomasiidae, and Astrapotheria. The metatherian Mammals are represented by a sparassodont, a palaeothentoid, and an argyrolagoid. This new Mammalian fauna preliminarily suggests a late middle Eocene age (Barrancan South American Land Mammal Age) for the Guabirotuba Formation.
Alfredo Armando Carlini - One of the best experts on this subject based on the ideXlab platform.
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Paleogene Land Mammal Faunas of South America; a Response to Global Climatic Changes and Indigenous Floral Diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, A Iglesias, Alfredo Armando Carlini, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored. The Paleogene floras of Patagonia and Chile show a climatic pattern that approximates that of North America, with an increase in both Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) from the Paleocene into the Early Eocene Climatic Optimum (EECO), although the Paleocene-Eocene Thermal Maximum (PETM) is not recognized in the available data set. Post-EECO temperatures declined in both regions, but more so in the north than the south, which also retained a higher rate of precipitation. The South American Paleogene Mammal faunas developed gradual, but distinct, changes in composition and diversity as the EECO was approached, but actually declined somewhat during its peak, contrary to the record in North America. At about 40 Ma, a post-EECO decline was recovered in both hemispheres, but the South American record achieved its greatest diversity then, rather than at the peak of the EECO as in the north. This post-EECO faunal turnover apparently was a response to the changing conditions when global climate was deteriorating toward the Oligocene. Under the progressively more temperate to seasonally arid conditions in South America, this turnover reflected a major change from the more archaic, and more tropical to subtropical-adapted Mammals, to the beginning of the ultimately modern South American fauna, achieved completely by the Eocene-Oligocene transition. Interestingly, hypsodonty was achieved by South American cursorial Mammals about 15–20 m.y. earlier than in North America. In addition to being composed of essentially different groups of Mammals, those of the South American continent seem to have responded to the climatic changes associated with the ECCO and subsequent conditions in a pattern that was initially comparable to, but subsequently different from, their North American counterparts.
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paleogene Land Mammal faunas of south america a response to global climatic changes and indigenous floral diversity
Journal of Mammalian Evolution, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Mariano Bond, Javier N. Gelfo, Guillermo M. López, Alfredo Armando Carlini, Ari Iglesias, Ana Natalia ZimiczAbstract:An appraisal of Paleogene floral and Land Mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Neotropical and Austral floras relative to North American counterparts. Conversely, the concurrent Mammal faunas in South America did not match, much less exceed, the diversity seen to the north. It appears unlikely that this difference is solely due to the virtual absence of immigrants subsequent to the initial dispersal of Mammals to South America, and cannot be explained solely by the different collecting histories of the two regions. Possible roles played by non-Mammalian vertebrates in niche exploitation remain to be explored.
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a new chronology for middle eocene early miocene south american Land Mammal ages
Geological Society of America Bulletin, 2013Co-Authors: Regan E Dunn, Alfredo Armando Carlini, Richard H. Madden, Mark D Schmitz, Matthew J Kohn, Caroline A E Stromberg, James L CrowleyAbstract:Cenozoic South American Land Mam- mal Ages (SALMAs) have historically been correlated to the geologic time scale using 40 Ar/ 39 Ar dating and magnetostratigraphy. At Gran Barranca (68.7°W, 45.7°S)—one of South America's key areas for constraining SALMAs—existing radioisotopic ages have uncertainties of up to 4 m.y. To better con- strain the ages of Mammalian assemblages, we employed high-precision (±<40 k.y.) U-Pb dating using single zircon crystals. We dated nine tuffs from the Sarmiento Formation containing middle Eocene-early Miocene faunas (Barrancan, Mustersan, Tinguiriri- can, Deseadan, Colhuehuapian, and "Pin- turan"). The new dates span from 39.861 ± 0.037 Ma to 19.041 ± 0.027 Ma. The La Can- cha Tuff, occurring within the Tinguirirican faunal level yielded an age of 33.581 ± 0.015 Ma, confi rming that the Vera Member con- tains the only fossiliferous geologic section encompassing the Eocene-Oligocene transi- tion in the Southern Hemisphere. The pre- Deseadan fauna, La Cantera, is ≤30.77 Ma, the age of the Colhuehuapian is expanded to 21.1-20.1 Ma, and the Pinturan may be as old as ca. 19 Ma. The new U-Pb dates confi rm that at- mospheric temperatures and vegetation remained constant across the Eocene- Oligocene transition in Patagonia and that hypsodonty occurred in South American un- gulates much earlier than on any other conti- nent. Additionally, refi nement of the SALMA boundaries will eventually provide the con- text necessary to compare faunal transitions across continents, although currently too much data are missing to allow such compar- isons. Finally, the new ages provide a high- resolution age model from which hypotheses about rates of environmental and evolution- ary change at Gran Barranca can be tested.
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Revised geochronology of the Casamayoran South American Land Mammal Age: climatic and biotic implications.
Proceedings of the National Academy of Sciences, 1999Co-Authors: Richard F. Kay, Alfredo Armando Carlini, Richard H. Madden, M. Guiomar Vucetich, Heizler M, Hamish A. SandemanAbstract:Isotopic age determinations (40Ar/39Ar) and associated magnetic polarity stratigraphy for Casamayoran age fauna at Gran Barranca (Chubut, Argentina) indicate that the Barrancan “subage” of the Casamayoran South American Land Mammal “Age” is late Eocene, 18 to 20 million years younger than hitherto supposed. Correlations of the radioisotopically dated magnetic polarity stratigraphy at Gran Barranca with the Cenozoic geomagnetic polarity time scale indicate that Barrancan faunal levels at the Gran Barranca date to within the magnetochronologic interval from 35.34 to 36.62 megannums (Ma) or 35.69 to 37.60 Ma. This age revision constrains the timing of an adaptive shift in Mammalian herbivores toward hypsodonty. Specifically, the appearance of large numbers of hypsodont taxa in South America occurred sometime between 36 and 32 Ma (late Eocene–early Oligocene), at approximately the same time that other biotic and geologic evidence has suggested the Southern high latitudes experienced climatic cooling associated with Antarctic glaciation.
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Revised geochronology of the Casamayoran South American Land Mammal Age: Climatic and biotic
1999Co-Authors: F. Kay, Alfredo Armando Carlini, Matthew T. Heizler, Richard H. Madden, M. Guiomar Vucetich, Mario M. Mazzoni, Hamish A. SandemanAbstract:Isotopic age determinations ( 40 Ary 39 Ar) and associated magnetic polarity stratigraphy for Casamayoran age fauna at Gran Barranca (Chubut, Argentina) indicate that the Barrancan ''subage'' of the Casamayoran South American Land Mammal ''Age'' is late Eocene, 18 to 20 million years younger than hitherto supposed. Correlations of the radioisotopically dated magnetic polarity stratigraphy at Gran Barranca with the Cenozoic geomagnetic polarity time scale indicate that Barrancan faunal levels at the Gran Barranca date to within the magnetochronologic interval from 35.34 to 36.62 megannums (Ma) or 35.69 to 37.60 Ma. This age revision constrains the timing of an adaptive shift in Mammalian herbivores toward hypsodonty. Specif- ically, the appearance of large numbers of hypsodont taxa in South America occurred sometime between 36 and 32 Ma (late Eocene- early Oligocene), at approximately the same time that other biotic and geologic evidence has suggested the Southern high latitudes experienced climatic cooling associated with Antarctic glaciation.
Édison V. Oliveira - One of the best experts on this subject based on the ideXlab platform.
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A New South American Paleogene Land Mammal Fauna, Guabirotuba Formation (Southern Brazil)
Journal of Mammalian Evolution, 2017Co-Authors: Fernando A. Sedor, Édison V. Oliveira, David D. Silva, Luiz A. Fernandes, Renata F. Cunha, Ana M. Ribeiro, Eliseu V. DiasAbstract:The Paleogene vertebrate-bearing sites of Brazil are restricted to few formations such as Maria Farinha (Late Cretaceous-early Paleocene), Itaboraí (early Eocene), Entre-Córregos (Eocene-Oligocene), and Tremembé (late Oligocene-early Miocene). A new Paleogene fauna is reported from an outcrop of the Guabirotuba Formation located at Curitiba, Paraná State, southern Brazil. The Guabirotuba Formation is a stratigraphic unit of the Curitiba Basin, which belongs to the Cenozoic continental rift system of southeastern Brazil, a predominantly half-graben and horst system. The sedimentary facies indicate a fluvial distributary depositional system associated with floodplain, generated under humid climate conditions alternating with drier periods. This new Paleogene fauna, here named the Guabirotuba Fauna, has invertebrate and vertebrate taxa, including Mammals (Cingulata, Notoungulata, Astrapotheria, and Metatheria). The fossil remains of seven armored xenarthrans are identified, including the description of a new species and genus named Proeocoleophorus carlinii . The Guabirotuba ungulates are assigned to Interatheriidae, Oldfieldthomasiidae, and Astrapotheria. The metatherian Mammals are represented by a sparassodont, a palaeothentoid, and an argyrolagoid. This new Mammalian fauna preliminarily suggests a late middle Eocene age (Barrancan South American Land Mammal Age) for the Guabirotuba Formation.
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A New South American Paleogene Land Mammal Fauna, Guabirotuba Formation (Southern Brazil)
Journal of Mammalian Evolution, 2016Co-Authors: Fernando A. Sedor, Édison V. Oliveira, Luiz A. Fernandes, Renata F. Cunha, Ana M. Ribeiro, D. T. Da Silva, Eliseu V. DiasAbstract:The Paleogene vertebrate-bearing sites of Brazil are restricted to few formations such as Maria Farinha (Late Cretaceous-early Paleocene), Itaborai (early Eocene), Entre-Corregos (Eocene-Oligocene), and Tremembe (late Oligocene-early Miocene). A new Paleogene fauna is reported from an outcrop of the Guabirotuba Formation located at Curitiba, Parana State, southern Brazil. The Guabirotuba Formation is a stratigraphic unit of the Curitiba Basin, which belongs to the Cenozoic continental rift system of southeastern Brazil, a predominantly half-graben and horst system. The sedimentary facies indicate a fluvial distributary depositional system associated with floodplain, generated under humid climate conditions alternating with drier periods. This new Paleogene fauna, here named the Guabirotuba Fauna, has invertebrate and vertebrate taxa, including Mammals (Cingulata, Notoungulata, Astrapotheria, and Metatheria). The fossil remains of seven armored xenarthrans are identified, including the description of a new species and genus named Proeocoleophorus carlinii. The Guabirotuba ungulates are assigned to Interatheriidae, Oldfieldthomasiidae, and Astrapotheria. The metatherian Mammals are represented by a sparassodont, a palaeothentoid, and an argyrolagoid. This new Mammalian fauna preliminarily suggests a late middle Eocene age (Barrancan South American Land Mammal Age) for the Guabirotuba Formation.
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Revised timing of the South American early Paleogene Land Mammal ages
Journal of South American Earth Sciences, 2014Co-Authors: Michael O. Woodburne, Francisco J. Goin, Javier N. Gelfo, María Sol Raigemborn, Matthew T. Heizler, Édison V. OliveiraAbstract:Abstract A new Ar/Ar date on the Las Flores Tuff (Rio Chico Group, Las Flores Fm., central Patagonia, Argentina) yielded an age of 49.512 ± 0.019 Ma. This tuff, which stratigraphically overlies the Mammal-bearing deposits that produced the Las Flores fauna, helps constrain the age of the Itaboraian SALMA [South American Land Mammal Age] to which that fauna is referred. The new data also have implications for the age of succeeding Mammal biochrons, such as the Riochican and “Sapoan” which are revised to being somewhat younger than previously interpreted. Although closer in age than formerly interpreted, they still are biotically distinct. Concomitant evaluations suggest that the Itaboraian SALMA is perhaps more contemporary with the EECO (Early Eocene Climatic Optimum) than previously considered. The Riochican may be interpreted as post-EECO, with its cooler climate consistent in that regard. A recent reconsideration of the chronology of elements of the Salamanca Formation resulted in the downward revision of the ages of the Peligran SALMA and the Carodnia Zone biochrons. These operations, together with our results, reflect a 9 m.y. gap in the late Paleocene and early Eocene Land Mammal record in South America.
