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Wyszukujesz frazę "Vizcaino, S.F." wg kryterium: Autor

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    Wyświetlanie 1-5 z 5
    Tytuł:
    Pleistocene burrows in the Mar del Plata area [Argentina] and their probable builders
    Autorzy:
    Vizcaino, S F
    Zarate, M.
    Bargo, M.S.
    Dondas, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/21211.pdf
    Data publikacji:
    2001
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Argentina
    burrow
    Mylodontidae
    deposit
    Pleistocene
    Mar del Plata area
    South America
    fossil animal
    Opis:
    Structures discovered near Mar del Plata are attributed to palaeoburrows built by fossil animals on the basis of morphological patterns, transgressive boundaries in relation to the sedimentary units, and the presence of claw marks on the walls and roofs. They are discrete features of several metres in length, and with subrounded cross sections. Their diameters range from 0.80 to 1.80 m, with the width generally exceeding the height. These structures occur in Pleistocene deposits containing mammals referable to the Ensenadan and Lujanian Ages. Several Xenarthra are good candidates as builders of these burrows. Palaeoburrows were attributed before to the large Pleistocene armadillos Propraopus, Eutatus, and Pampatherium. We consider the possibility that the mylodontid ground sloths were responsible for excavating the burrows. The similar diameters of the burrows and the sloths are consistent with this observation. Anatomical, allometric, and biomechanical analysis of sloths limbs indicates that they were well designed to perfonn such activity. The shape of some claw marks preserved on the sides and roof of the burrows fits the form of their hand skeleton. Thus, the mylodontid sloths Scelidotherium and Glossotherium are considered as possible builders for the large late Cenozoic burrows present in the Pampean region.
    Źródło:
    Acta Palaeontologica Polonica; 2001, 46, 2
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mass estimation of Santacrucian sloths from the Early Miocene Santa Cruz Formation of Patagonia, Argentina
    Autorzy:
    Toledo, N.
    Cassini, G.H.
    Vizcaino, S.F.
    Bargo, M.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/946022.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    mammalia
    xenarthra
    folivora
    santacrucian sloths
    body mass
    substrate preference
    paleobiology
    miocene
    argentina
    Opis:
    Miocene deposits of the Santa Cruz Formation, Patagonia, comprise a diverse and excellently preserved vertebrate fauna, allowing detailed paleobiological and paleoecological studies based on three ecological parameters: body mass, diet, and substrate preference. In contrast to the small and arboreal extant sloths, Bradypus and Choloepus, Santacrucian sloths were much more diverse and larger, and comprised 11 genera previously characterized as arboreal or climbing forms. Here, we focus on body mass estimation based on measurements of postcranial elements. We present a morphometric database comprising 64 linear, base-ten logged variables applied to Santacrucian sloths and a wide sample of extant mammals, as well as the body mass of the extant taxa as reported in the literature. To detect any potential phylogenetical bias, we performed a variance decomposition test on our sample of extant mammals. Based on four orthogram statistics, logged body mass was found not to be dependent on phylogenetic tree topology. Predictive equations for the body mass of extant mammals were generated through multiple regression analysis, using weighting procedures to avoid taxonomic biases and stepwise analysis to discard redundant variables. Using this procedure, we derived separate equations for the scapula, humerus, radius, ulna, pelvis, femur, tibia plus fibula, astragalus, and calcaneum. These equations were then applied to estimate the body mass of our sample of Santacrucian sloths. We obtained an average body mass of about 70 kg for the megalonychid Eucholoeops. Among stem megatherioids, Hapalops ranged between 30 and 80 kg, Analcimorphus was estimated at 67 kg, and Schismotherium at 44 kg. Larger genera included the megatheriid Prepotherium (~123 kg), and the mylodontids Analcitherium (~88 kg) and Nematherium (~89 kg). The medium to large body size of Santacrucian sloths imposed constraints on their climbing abilities. Megalonychids and stem megatherioids were likely unable to access the finest branches, while megatheriids and mylodonts were more terrestrial forms.
    Źródło:
    Acta Palaeontologica Polonica; 2014, 59, 2; 267-280
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Paleoecology of the large carnivore guild from the late Pleistocene of Argentina
    Autorzy:
    Prevosti, F.J.
    Vizcaino, S.F.
    Powiązania:
    https://bibliotekanauki.pl/articles/23538.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Carnivora
    carnivore
    Late Pleistocene
    Pleistocene
    South America
    paleoecology
    population density
    Argentina
    paleontology
    fossil carnivore
    locality
    biomass
    ecology
    Opis:
    The paleoecology of the South American fossil carnivores has not been as well studied as that of their northern relatives. One decade ago Fariña suggested that the fauna of Río Luján locality (Argentina, late Pleistocene–early Holocene) is not balanced because the metabolic requirements of the large carnivores are exceeded by the densities and biomass of the large herbivores. This conclusion is based on the calculation of densities using allometric functions between body mass and population abundance, and is a consequence of low carnivore richness versus high herbivore richness. In this paper we review the carnivore richness in the Lujanian of the Pampean Region, describe the paleoecology of these species including their probable prey choices, and review the available information on taphonomy, carnivore ecology, and macroecology to test the hypothesis of “imbalance” of the Río Luján fauna. The carnivore richness of the Río Luján fauna comprises five species: Smilodon populator, Panthera onca, Puma concolor, Arctotherium tarijense, and Dusicyon avus. Two other species are added when the whole Lujanian of the Buenos Aires province is included: Arctotherium bonariense and Canis nehringi. With the exception of D. avus and Arctotherium, these are hypercarnivores that could prey on large mammals (100–500 kg) and juveniles of megamammals (>1000 kg). S. populator could also hunt larger prey with body mass between 1000 and 2000 kg. The review of the “imbalance” hypothesis reveals contrary evidence and allows the proposal of alternative hypotheses. If high herbivore biomass occurred during the Lujanian, a higher density of carnivores could be supported than as inferred from the power function of body size and population density.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Carved teeth and strange jaws: how glyptodonts masticated
    Autorzy:
    Farina, R A
    Vizcaino, S F
    Powiązania:
    https://bibliotekanauki.pl/articles/20133.pdf
    Data publikacji:
    2001
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    glyptodont
    biomechanics
    paleobiology
    tooth
    strange jaw
    jaw mechanics
    South America
    Opis:
    In this paper, the highly peculiar masticatory apparatus of glyptodonts is studied. The general morphology of the skull is analysed using a morphometric procedure, the Resistant Fit Theta Rho Analysis, which allows comparison among different biological forms. Here, a large terminal form, the late Pleistocene genus Glyptodon, is compared with the smaller primitive Miocene genus Propalaehoplophorus, and with the generalised Recent armadillo Chaetophractus. The masticatory musculature of glyptodonts is reconstructed. Their tooth form and wear facets, as well as their mandibular symphysis and jaw joint, are analysed. A model of jaw movement is constructed based on these analyses. It is demonstrated that the masticatory apparatus of glyptodonts had undergone a telescoping process, which was already underway in the most ancient forms whose skull is known. This process created problems in regard to the way stresses produced by mastication were absorbed by the mandible, and therefore it might be regarded as non-adaptive. Some functional explanatory hypotheses are discussed, such as a requirement of keeping the moment of the weight of the cranium small enough to be counterbalanced by the neck muscles, or fitting the head into the armour.
    Źródło:
    Acta Palaeontologica Polonica; 2001, 46, 2
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hypsodonty in Pleistocene ground sloths
    Autorzy:
    Bargo, M S
    De Iuliis, G.
    Vizcaino, S.F.
    Powiązania:
    https://bibliotekanauki.pl/articles/21985.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    diet
    Xenarthra
    habitat
    habit
    hypsodonty
    sloth
    Pleistocene
    Tardigrada
    paleontology
    Opis:
    Although living sloths (Xenarthra, Tardigrada) are represented by only two genera, their fossil relatives form a large and diverse group. The evolution of hypsodonty, the crown height of a tooth, has traditionally been viewed as a response to dietary shifts toward abrasive vegetation. But recent work indicates that hypsodonty is also due to the higher prevalence of grit and dust in more open environments. The teeth of sloths are both high−crowned and open−rooted, or hypselodont, but distinctions between the selective factors acting to produce differing degrees of hypsodonty have not been rigorously considered. A comparative analysis of hypsodonty was performed in eleven species of Pleistocene sloths. It suggests that differences in hypsodonty may be explained by dietary preferences, habitat and habits. Among mylodontids, morphologic and biomechanical analyses indicate that hypsodonty was unlikely to be due solely to feeding behavior, such as grazing. Some mylodontids (e.g., Scelidotherium leptocephalum, Lestodon armatus, Glossotherium robustum, Mylodon darwini) were capable diggers that likely dug for food, and ingestion of abrasive soil particles probably played a considerable role in shaping their dental characteristics. Increased hypsodonty over time in Paramylodon harlani, however, is apparently due to a change in habitat from closed to more open environments. Geographical distributions of the megatheriids Eremotherium and Megatherium indicate differing habitats as possible factors in hypsodonty differences. In summary, among Tardigrada hypsodonty is apparently affected by diet, habitat and habit. The absence of enamel must be responsible for much of the hypsodonty observed in xenarthrans, which obscures the interpretation of contribution of each of the mentioned factors.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 1
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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