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Mino-Boilini A.R.,CONICET | Tomassini R.L.,CONICET | Oliva C.,Museo Municipal de Ciencias Naturales Carlos Darwin | de Bianco T.M.,National University of the South
Revista Brasileira de Paleontologia | Year: 2011

The Scelidotheriinae subfamily constitutes a little diversified monophyletic group within the Mylodontidae, with a biochron that spans from the middle Miocene to the early Holocene. During the Huayquerian- Chapadmalalan age (late Miocene-middle Pliocene) the Scelidotheriinae are only represented by the genus Proscelidodon, being P. patrius the only species recognized for the Montehermosan stage/age (late Miocene-early Pliocene). Due to the scarcity of findings, the knowledge of the Neogene taxa included in this subfamily is limited, especially regarding the anatomical study of the postcranial skeleton. In this opportunity, the authors present the finding of a left hind limb partially complete in good condition of conservation, of an adult individual, assigned to Proscelidodon cf. P. patrius (Ameghino). The material was unearthed from the fluvial deposits of Monte Hermoso Formation (Buenos Aires, Argentina), in silty levels that represent flooding plain facies and that, biostratigraphically, correspond to Montehermosean stage/age. The detailed anatomical study of the different skeletal elements recovered, added to the comparison with other representative elements of this subfamily, provides novel data about the postcranial characteristics of Proscelidodon and allows us to evaluate its taxonomic and paleoecologic implications. © 2011 by the Sociedade Brasileira de Paleontologia. Source

Tomassini R.L.,National University of La Pampa | Agnolin F.,Maimonides University | Agnolin F.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Oliva C.,Museo Municipal de Ciencias Naturales Carlos Darwin
Journal of Vertebrate Paleontology | Year: 2011

The first fossil occurrence of the genus Lepidobatrachus is reported. The specimen comes from the Farola Monte Hermoso locality (Buenos Aires Province, Argentina), more specifically from the early Pliocene levels of the Monte Hermoso Formation. The specimen belongs to the living species L. laevis, a frog that currently inhabits the Chacoan region of northern Argentina, Paraguay, and Bolivia. The presence of this anuran represents the southernmost record for the genus Lepidobatrachus, and is in agreement with previous hypothesis suggesting that during the Pliocene the climatic environmental conditions of the southern Pampas were likely those of the modern Chacoan region. The disjunct distribution of extant L. laevis suggests that the retraction of Chacoan areas to the north modified the former distribution of this taxon, and that its current geonemy may represent relics of a formerly more extensive geographic distribution. © 2011 by the Society of Vertebrate Paleontology. Source

Isolated osteoderms of the dorsal carapace of the dasypodid Macrochorobates scalabrinii (Moreno & Mercerat) are described. The remains come from the upper deposits of the Las Flores Formation (Upper Miocene), outcropping at the Iglesia Valley (Iglesia Department, San Juan Province, Argentina). The detailed study of these osteoderms, including the description of some features not mentioned before, provides novel information about the carapace that may potentially be important for the diagnosis of this taxon. The stratigraphic and chronological distribution would support the importance of M. scalabrinii as a biostratigraphic indicator for the Huayquerian Stage/Age. This new discovery confirms previous hypothesis of a biogeographic connection between the Pampean and Northwest regions during the late Miocene. © 2013 by the Sociedade Brasileira de Paleontologia. Source

Tomassini R.L.,CONICET | Montalvo C.I.,National University of La Pampa | Deschamps C.M.,CIC | Manera T.,Museo Municipal de Ciencias Naturales Carlos Darwin
Journal of South American Earth Sciences | Year: 2013

The Monte Hermoso Formation, cropping out at its type locality of Farola Monte Hermoso (Buenos Aires Province), is a classical fossiliferous unit of the South American Neogene, highlighted by the abundance and diversity of its vertebrate remains. However, its biostratigraphy and age have been largely debated, and numerous discrepancies and controversies have been stated. In this regard, the result of the analysis of new materials recovered from the different levels of this formation, following a strict control of stratigraphic provenance, is here reported. As well, the provenance of specimens of previous collections has been evaluated. The studied assemblage consists of Osteichthyes, Amphibia, Reptilia, Aves and Mammalia. These latter are the most numerous and belong to the Didelphimorphia, Polydolopimorphia, Rodentia, Notoungulata, Litopterna and Xenarthra. The recorded taxa suggest no important faunistic variations among the different levels of the Monte Hermoso Formation that would imply significant chronological differences, and hence, justify the recognition of two biostratigraphic units. The analysis of the first and last records as well as the taxa considered as exclusive, does not support the validity of the biozones of Trigodon gaudryi and Neocavia depressidens previously proposed. On this basis, a new scheme for the Monte Hermoso Formation at its type locality is proposed, including a new single biostratigraphic unit. This unit is the Eumysops laeviplicatus Range Zone, which represents the biostratigraphic base for the Montehermosan Stage/Age of the early Pliocene. © 2013 Elsevier Ltd. Source

Tomassini R.L.,CONICET | Tomassini R.L.,National University of La Pampa | Montalvo C.I.,National University of La Pampa | Manera T.,National University of the South | Oliva C.,Museo Municipal de Ciencias Naturales Carlos Darwin
Ameghiniana | Year: 2010

Results are presented of a comparative taphonorruc study conducted on mammal remains from Playa del Barco, Buenos Aires Province, Argentina. Two bearing levels, belonging to a fluvial environment were recognized: one constituted mainly by conglomerates and the other by silty sandstones. The mammal remains collected belong to the orders Xenarthra, Notoungulata, Litopterna, Rodentia, Carnivora, Perissodactyla, Artiodactyla, and Proboscidea, all of them components of the typical Pleistocene megafauna. When taking into account the source level, variations in the taphonomic attributes of the analysed materials were observed. Remains from the conglomerate show evidence of having been rapidly buried and then reelaborated before their final deposition. Fossils from silty sandstones show signs of longer exposure to weather, more intensely subject to processes that took place before burial. Due to their characteristics they are interpreted as re-deposited remains. In both cases, processes related to mass transport are inferred. Nevertheless, the diversity in conservation status and taphonomic attributes would result from processes originated at each of the source levels. The lithostratigraphic, taxonomie, and taphonomic evidences do not allow relating these two levels to a unique event. Therefore, the fossils that they contain are interpreted as members of two different associations. © Asociación Paleontológica Argentina. Source

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