The largest known bear, Arctotherium angustidens, from the early Pleistocene Pampean region of Argentina: with a discussion of size and diet trends in bears

2011 ◽  
Vol 85 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Leopoldo H. Soibelzon ◽  
Blaine W. Schubert
Keyword(s):  
South America ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Buenos Aires Province ◽  
South American ◽  
Pampean Region ◽  
Great American Biotic Interchange ◽  
Epiphyseal Fusion ◽  
Evolutionary Trajectories ◽  
Serious Injuries

The South American giant short-faced bear (Arctotherium angustidens Gervais and Ameghino, 1880) is one of five described Arctotherium species endemic to South America and it is known for being the earliest, largest, and most carnivorous member of the genus. Here we report an extraordinarily large A. angustidens individual exhumed from Ensenadan sediments (early to middle Pleistocene) at Buenos Aires Province, Argentina. Based on overall size, degree of epiphyseal fusion, and pathologies, this bear was an old-aged male that sustained serious injuries during life. Body mass of the bear is estimated and compared to other ursid species based on a series of allometric equations. To our knowledge, this specimen now represents the largest bear ever recorded. In light of this discovery, we discuss the evolution of body size in Arctotherium (from large-to-small) and compare this to bears that exhibited different evolutionary trajectories. We suggest that the larger size and more carnivorous nature of A. angustidens, compared to later members of the genus, may reflect the relative lack of other large carnivores and abundance of herbivores in South America just after the Great American Biotic Interchange.

scholarly journals New radiometric 40Ar–39Ar dates and faunistic analyses refine evolutionary dynamics of Neogene vertebrate assemblages in southern South America

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Francisco J. Prevosti ◽  
Cristo O. Romano ◽  
Analía M. Forasiepi ◽  
Sidney Hemming ◽  
Ricardo Bonini ◽  
...  
Keyword(s):  
South America ◽  
Evolutionary Dynamics ◽  
Atlantic Coast ◽  
Buenos Aires Province ◽  
South American ◽  
Important Place ◽  
Faunal Turnover ◽  
Great American Biotic Interchange ◽  
Late Neogene ◽  
Main Basis

AbstractThe vertebrate fossil record of the Pampean Region of Argentina occupies an important place in South American vertebrate paleontology. An abundance of localities has long been the main basis for constructing the chronostratigraphical/geochronological scale for the late Neogene–Quaternary of South America, as well as for understanding major patterns of vertebrate evolution, including the Great American Biotic Interchange. However, few independently-derived dates are available for constraining this record. In this contribution, we present new 40Ar/39Ar dates on escorias (likely the product of meteoric impacts) from the Argentinean Atlantic coast and statistically-based biochronological analyses that help to calibrate Late Miocene–Pliocene Pampean faunal successions. For the type areas of the Montehermosan and Chapadmalalan Ages/Stages, our results delimit their age ranges to 4.7–3.7 Ma and ca. 3.74–3.04 Ma, respectively. Additionally, from Buenos Aires Province, dates of 5.17 Ma and 4.33 Ma were recovered for “Huayquerian” and Montehermosan faunas. This information helps to better calibrate important first appearances of allochthonous taxa in South America, including one of the oldest records for procyonids (7.24–5.95 Ma), cricetids (6.95–5.46 Ma), and tayassuids (> 3.74 Ma, oldest high-confidence record). These results also constrain to ca. 3 Ma the last appearances of the autochthonous sparassodonts, as well as terror birds of large/middle body size in South America. South American faunal turnover during the late Neogene, including Late Pliocene extinctions, is interpreted as a consequence of knock-on effects from global climatic changes and initiation of the icehouse climate regime.

Middle Pleistocene age of the fossiliferous sedimentary sequence from Tarija, Bolivia

2013 ◽  
Vol 79 (2) ◽  
pp. 268-273 ◽  
Author(s):  
Bruce J. MacFadden ◽  
Peter K. Zeitler ◽  
Federico Anaya ◽  
John M. Cottle
Keyword(s):  
South America ◽  
New Age ◽  
Middle Pleistocene ◽  
South American ◽  
Sedimentary Sequence ◽  
The Past ◽  
Reference Sections ◽  
Great American Biotic Interchange ◽  
New Interpretation ◽  
Land Mammal

AbstractThe highly fossiliferous sediments of the Tolomosa Formation from Tarija, southern Bolivia, represent one of the most important localities in South America that documents the Great American Biotic Interchange. Over the past several decades, chronostratigraphic studies have indicated a middle Pleistocene age for the Tolomosa Formation from ~ 1.1 to 0.7 Ma. This interval correlates to the Ensenadan South American Land Mammal Age as it is characterized from classic localities in Argentina. Recently, however, a new interpretation based on AMS 14C ages indicates that the fossiliferous sediments from Tarija are latest Pleistocene, i.e., < 44 ka, and thus of Lujanian age. Here we report a new age of 0.76 ± 0.03 Ma (2σ) based on 11 U–Th/Pb and U–Th/He individual determinations from the Tolomosa Formation. This is indistinguishable from the age published from the same ash in 1983, and was originally used to calibrate the magnetostratigraphic section at Tarija. The new age confirms that the age of the Tolomosa Formation is middle Pleistocene, and not latest Pleistocene. The age of the Tarija Fauna has significant implications with regard to the stage of evolution biochronology for Pleistocene fossil mammals in South America, and in particular, the classic and important reference sections in Argentina.

scholarly journals South American giant short-faced bear (Arctotherium angustidens) diet: evidence from pathology, morphology, stable isotopes, and biomechanics

2014 ◽  
Vol 88 (6) ◽  
pp. 1240-1250 ◽  
Author(s):  
Leopoldo H. Soibelzon ◽  
Gustavo A. Grinspan ◽  
Hervé Bocherens ◽  
Walter G. Acosta ◽  
Washington Jones ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
South America ◽  
Body Mass ◽  
Great Power ◽  
Middle Pleistocene ◽  
South American ◽  
Geometric Morphometric ◽  
Large Size ◽  
Dental Pathology ◽  
Great American Biotic Interchange

Arctotherium angustidensGervais and Ameghino, 1880 (the South American giant short-faced bear) is known for being the earliest (Ensenadan Age, early to middle Pleistocene) and largest (body mass over 1 ton) of five describedArctotheriumspecies endemic to South America. Here we assess the diet of this bear from multiple proxies: morphology, biomechanics, dental pathology, stable isotopes and a previous study using geometric morphometric methodology. Results favor the idea of animal matter consumption, probably from large vertebrates in addition to vegetable matter consumption. Most probably, active hunting was not the unique strategy of this bear for feeding, since its large size and great power may have allowed him to fight for the prey hunted by other Pleistocene carnivores. However, scavenging over mega mammal carcasses was probably another frequent way of feeding. South American short-faced bears adjusted their size and modified their diet through Pleistocene times, probably as a response to the diversification of the carnivore guild (from the few precursory taxa that crossed the Panamanian Isthmus during the Great American Biotic Interchange).

scholarly journals Pleistocene Mammals from Pampean Region (Argentina). Biostratigraphic, Biogeographic, and Environmental Implications

Quaternary ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 15
Author(s):  
José Luis Prado ◽  
María Teresa Alberdi ◽  
Jonathan Bellinzoni
Keyword(s):  
South America ◽  
The State ◽  
Historical Study ◽  
South American ◽  
Environmental Implications ◽  
Sedimentary Sequences ◽  
Pampean Region ◽  
Mammalian Faunas ◽  
Pleistocene Mammals ◽  
Fossil Records

The Pampean Region contains sedimentary sequences with abundant mammal fossil records, which constitute the chronological outline of the Plio–Pleistocene of South America. These classic localities have been used for more than a century to correlate with other South American regions. Throughout this time, a series of misinterpretations have appeared. To understand the stratigraphic significance of these localities and the geochronological situation of each unit referring to the Pleistocene, a critical historical study of the antecedents was carried out, evaluating the state of each unit. The biostratigraphic studies of the Pampean Region’s mammalian faunas improved the understanding of biogeographic changes taking into account the environmental fluctuations of the Pleistocene.

Chronostratigraphy and “Land-Mammal Ages” in the Cenozoic of southern South America: principles, practices, and the “Uquian” problem

1995 ◽  
Vol 69 (1) ◽  
pp. 135-159 ◽  
Author(s):  
Alberto L. Cione ◽  
Eduardo P. Tonni
Keyword(s):  
South America ◽  
Buenos Aires ◽  
New South ◽  
Lower Boundary ◽  
Buenos Aires Province ◽  
South American ◽  
Southern South America ◽  
Matuyama Chron ◽  
Study Case ◽  
Land Mammal

The concept of “land-mammal age” as developed in South America is examined. The “Uquian Land-mammal age” is used as a study case. “Land-mammal age” parataxonomy is here considered methodologically but not conceptually different from chronostratigraphic taxonomy. “Land-mammal ages” in South America are based on stages. However, we consider that accurate biostratigraphic studies must be done in South America for establishing the biostratigraphy and precise boundary stratotypes of most stages-ages. The Uquia outcrops are here considered inadequate as a stratotype. A new South American continental stage-age is proposed. This stage is based on a biostratigraphic scheme. The stratotypes of the stage and biozones are located in the fossiliferous southeastern Buenos Aires Province marine cliffs. The lower boundary stratotype is proposed. The stage-age is probably correlated with the Gauss Chron and the lower Matuyama Chron. Additionally, some major units of Ameghino are validated and a different timing for the arrival of North American mammals to southern South America is presented.

scholarly journals A Pliocene–Pleistocene continental biota from Venezuela

2021 ◽  
Vol 140 (1) ◽  
Author(s):  
Jorge D. Carrillo-Briceño ◽  
Rodolfo Sánchez ◽  
Torsten M. Scheyer ◽  
Juan D. Carrillo ◽  
Massimo Delfino ◽  
...  
Keyword(s):  
Fossil Record ◽  
Climatic Changes ◽  
Early Pleistocene ◽  
South American ◽  
Late Pliocene ◽  
Bony Fishes ◽  
Great American Biotic Interchange ◽  
Stratigraphic Position ◽  
Dry Conditions ◽  
First Time

AbstractThe Pliocene–Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86Sr/88Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.

scholarly journals Fossil horses from the Late Pleistocene of Tapalqué Creek (Buenos Aires Province, Argentina)

2019 ◽  
Vol 294 (3) ◽  
pp. 285-305
Author(s):  
José L. Prado ◽  
Ricardo Bonini ◽  
Cristian Favier-Dubois ◽  
Gustavo N. Gómez ◽  
Pamela Steffan ◽  
...  
Keyword(s):  
South America ◽  
Buenos Aires ◽  
Buenos Aires Province ◽  
South American ◽  
Fluvial Deposits ◽  
Sedimentary Deposits ◽  
Diagenetic Processes ◽  
Taphonomic Analysis ◽  
Land Mammal ◽  
New Evidence

A comparative study was made with the known record of equids species in South America, identifying the remains as Equus neogeus, Hippidion devillei, and Hippidion principale. These data increase the record of Equidae in South America and provide new evidence about the chronological and geographical distribution. The sedimentary deposits of the Lujan Formation outcropping at Tapalqué creek (4 to 120 ky) were accumulated through fluvial processes. This Formation comprises a rich vertebrate fauna corresponding to the Lujanian South American Land Mammal Age, which includes numerous and diverse vertebrate remains. The taphonomic analysis indicates that the faunistic assemblage was formed and was subject to diagenetic processes without distinction of its action in the fossiliferous levels, that can be recognized as fluvial deposits.

scholarly journals A new stage in the Upper Cenozoic of Southern South America

1992 ◽  
Vol 6 ◽  
pp. 56-56
Author(s):  
Alberto L. Cione ◽  
Eduardo P. Tonni
Keyword(s):  
South America ◽  
Buenos Aires ◽  
New South ◽  
Lower Boundary ◽  
Geographic Location ◽  
Buenos Aires Province ◽  
South American ◽  
Southern South America ◽  
Matuyama Chron ◽  
Upper Cenozoic

Former workers developed in South America a chronostratigraphic system not essentially different to that of European stage/age system. However, the authors of this paper believe that accurate biostratigraphic studies have to be done in southern South America for establishing the precise boundary stratotypes of most stage/ages. A new South American Upper Cenozoic continental stage/age is recognized. The stratotype is located in the fossiliferous southeastern Buenos Aires Province marine cliffs between Mar del Plata and Miramar. The outcrops in the area are the best continental representation of Plio-Pleistocene times in South America. It is younger than Chapadmalalan and older than Ensenadan and replaces the “Uquian”. We consider that the “Uquian” actually emcopasses Chapadmalalan and Ensenadan times. The Uquía outcrops are here considered inadequate as stratotype especially by the dearth of micromanmals, the relatively poor fossil record and the comparatively inadequate geographic location. The new stage would be correlated with the Gauss Chron and possibly with the lower Matuyama Chron. The lower boundary is tentatively stated. For so doing, a biostratigraphic scheme is proposed. This lower boundary approximately corresponds to the base of the Barranca de los Lobos “Formation” of Kraglievich (1952) and a new (unpublished) unconformity bounded unit (Zárate, 1989). Some taxa that apparently ranges from the base are candidates to define it after a detailed biostratigraphic study.Additionally, a different timing for the arrival of North American mammals to southern South America is given.

scholarly journals Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America

2016 ◽  
Vol 12 (4) ◽  
pp. 20160062 ◽  
Author(s):  
Kieren J. Mitchell ◽  
Sarah C. Bray ◽  
Pere Bover ◽  
Leopoldo Soibelzon ◽  
Blaine W. Schubert ◽  
...  
Keyword(s):  
South America ◽  
North American ◽  
Convergent Evolution ◽  
Phylogenetic Analyses ◽  
Early Pleistocene ◽  
South American ◽  
The North ◽  
Molecular Phylogenetic ◽  
North And South America ◽  
North And South

The Tremarctinae are a subfamily of bears endemic to the New World, including two of the largest terrestrial mammalian carnivores that have ever lived: the giant, short-faced bears Arctodus simus from North America and Arctotherium angustidens from South America (greater than or equal to 1000 kg). Arctotherium angustidens became extinct during the Early Pleistocene, whereas Arctodus simus went extinct at the very end of the Pleistocene. The only living tremarctine is the spectacled bear ( Tremarctos ornatus ), a largely herbivorous bear that is today only found in South America. The relationships among the spectacled bears ( Tremarctos ), South American short-faced bears ( Arctotherium ) and North American short-faced bears ( Arctodus ) remain uncertain. In this study, we sequenced a mitochondrial genome from an Arctotherium femur preserved in a Chilean cave. Our molecular phylogenetic analyses revealed that the South American short-faced bears were more closely related to the extant South American spectacled bear than to the North American short-faced bears. This result suggests striking convergent evolution of giant forms in the two groups of short-faced bears ( Arctodus and Arctotherium ), potentially as an adaptation to dominate competition for megafaunal carcasses.

scholarly journals Disproportionate extinction of South American mammals drove the asymmetry of the Great American Biotic Interchange

2020 ◽  
Vol 117 (42) ◽  
pp. 26281-26287 ◽  
Author(s):  
Juan D. Carrillo ◽  
Søren Faurby ◽  
Daniele Silvestro ◽  
Alexander Zizka ◽  
Carlos Jaramillo ◽  
...  
Keyword(s):  
South America ◽  
North American ◽  
Biotic Interactions ◽  
South American ◽  
Dispersal Rate ◽  
Great American Biotic Interchange ◽  
Drastic Increase ◽  
The Asymmetry ◽  
North And South America ◽  
North And South

The interchange between the previously disconnected faunas of North and South America was a massive experiment in biological invasion. A major gap in our understanding of this invasion is why there was a drastic increase in the proportion of mammals of North American origin found in South America. Four nonmutually exclusive mechanisms may explain this asymmetry: 1) Higher dispersal rate of North American mammals toward the south, 2) higher origination of North American immigrants in South America, 3) higher extinction of mammals with South American origin, and 4) similar dispersal rate but a larger pool of native taxa in North versus South America. We test among these mechanisms by analyzing ∼20,000 fossil occurrences with Bayesian methods to infer dispersal and diversification rates and taxonomic selectivity of immigrants. We find no differences in the dispersal and origination rates of immigrants. In contrast, native South American mammals show higher extinction. We also find that two clades with North American origin (Carnivora and Artiodactyla) had significantly more immigrants in South America than other clades. Altogether, the asymmetry of the interchange was not due to higher origination of immigrants in South America as previously suggested, but resulted from higher extinction of native taxa in southern South America. These results from one of the greatest biological invasions highlight how biogeographic processes and biotic interactions can shape continental diversity.

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