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Wyświetlanie 1-4 z 4
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
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:
Anisodontherium from the Late Miocene of north-western Argentina
Autorzy:
Brandoni, D.
Powell, J.E.
Gonzales, O.E.
Powiązania:
https://bibliotekanauki.pl/articles/20115.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Anisodontherium
Late Miocene
Miocene
paleontology
Argentina
Xenarthra
Megatheriinae
ground sloth
diversity
Upper Miocene
Opis:
The fossil record of Megatheriinae (Tardigrada, Megatheriidae) in Argentina extends from the Colloncuran (Middle Miocene of Patagonia) to the Lujanian (Late Pleistocene–Early Holocene of the Pampean region). In the Late Miocene of north−western Argentina, Megatheriinae is represented by just three species belonging to a single genus, Pyramiodontherium. Here, we describe a partial mandible and the phalanges of a third digit of the manus recovered from the Saladillo Formation (Upper Miocene) of Tucumán Province, and assign them to Anisodontherium sp. Anisodontherium is primarily characterized by mesiodistally compressed molariforms, an anterior margin of the coronoid process located posterior to m4, and a posterior margin of the mandibular symphysis located anterior to m1. While these features can also be observed in A. halmyronomum from the Arroyo Chasicó Formation (Buenos Aires Province, Pampean region), Anisodontherium sp. is smaller and more slender than the former. The shape of each molariform of Anisodontherium affects the total length of the molariform tooth row, and thus the interpretation of some characters used in cladistic and paleobiological analyses. The material described here adds to the knowledge of the mandibular and dental anatomy of early megatheriines. In addition, the occurrence of Anisodotherium in Tucumán Province provides the first record of this genus outside the Pampean region, and increases the diversity of megatheriines during the Late Miocene–Pliocene of north−western Argentina.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The ground sloth Megatherium americanum: skull shape, bite forces, and diet
Autorzy:
Bargo, M S
Powiązania:
https://bibliotekanauki.pl/articles/23343.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Xenarthra
mastication
Megatherium americanum
behaviour
biomechanics
skull shape
morphology
dietary component
South America
diet
fossil
Megatherium
dietary habit
Pleistocene
fibrous food
Glossotherium robustum
Tardigrada
Bradypus variegatus
Opis:
Megatherium americanum (late Pleistocene of South America) has traditionally been regarded a herbivore, but its dietary habits have not been considered in terms of a morphofunctional analysis. This study describes and analyses the morphology of the masticatory apparatus in order to interpret the jaw mechanics of M. americanum, and thus to infer its diet and behaviour. The results are compared with those for the mylodontid Glossotherium robustum and the extant sloth Bradypus variegatus. The areas of origin and insertion of the masticatory musculature were reconstructed, and the moment arms generated by this musculature were estimated so that the mechanics of the feeding apparatus might be described. These analyses indicate that M. americanum was well adapted for strong and mainly vertical biting. The teeth are extremely hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests that the teeth were used mainly for cutting, rather than grinding, and that hard and fibrous food was not the main dietary component. The diet of M. americanum merits more rigorous analysis, but the evidence provided here indicates that it probably had a browsing diet in open habitats, but also could have fed on moderate to soft tough food.
Źródło:
Acta Palaeontologica Polonica; 2001, 46, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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