Oligocene
Mostrando 13-24 de 30 artigos, teses e dissertações.
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13. A finding of Oligocene primates on the European continent
In this paper, we provide evidence that contrary to the current view, primates on the European continent did survive the dramatic extinction/origination event across the Eocene/Oligocene boundary 34 million years ago that severely affected the Eurasian mammal communities (the European “Grande Coupure” and the Asian “Mongolian Remodeling”). The surviv
The National Academy of Sciences.
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14. The cranium of Parapithecus grangeri, an Egyptian Oligocene anthropoidean primate
A nearly complete skull of Parapithecus grangeri from the early Oligocene of Egypt is described. The specimen is relatively undistorted and is undoubtedly the most complete higher primate skull yet found in the African Oligocene, which also makes it the most complete Oligocene primate cranium worldwide. Belonging in superfamily Parapithecoidea, a group regar
The National Academy of Sciences.
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15. Taxeopody in the carpus and tarsus of Oligocene Pliohyracidae (Mammalia: Hyracoidea) and the phyletic position of hyraxes.
Recent hyracoids and elephants share a taxeopode arrangement of tarsal and carpal bones, a condition in which bones are aligned with minimal interlocking between adjacent elements. Taxeopody has often been interpreted as a synapomorphy reflecting a close phyletic link between Hyracoidea and Proboscidea, but recently it has been suggested [Fischer, M. S. (198
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16. Decoupled taxonomic radiation and ecological expansion of open-habitat grasses in the Cenozoic of North America
Because of a dearth of Cenozoic grass fossils, the timing of the taxonomic diversification of modern subclades within the grass family (Poaceae) and the rise to ecological dominance of open-habitat grasses remain obscure. Here, I present data from 99 Eocene to Miocene phytolith assemblages from the North American continental interior (Colorado, Nebraska, Wyo
National Academy of Sciences.
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17. Evolution of seahorses' upright posture was linked to Oligocene expansion of seagrass habitats
Seahorses (Syngnathidae: Hippocampus) are iconic marine teleosts that are readily identifiable by their upright posture. The fossil record is inadequate to shed light on the evolution of this trait because it lacks transitional forms. There are, however, extant syngnathid species (the pygmy pipehorses) that look like horizontally swimming seahorses and that
The Royal Society.
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18. THE COMPOSITION OF FOSSIL OYSTER SHELL PROTEINS*
Analyses of the protein residues recovered from fossil oyster shells of ages from the Pleistocene through the Cretaceous show substantially the same amino acids as are present in modern proteins. The amount of these residues declines sharply to the Oligocene, after which it proceeds more slowly. These older proteins contain relatively less aspartic acid and
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19. Genomic data support the hominoid slowdown and an Early Oligocene estimate for the hominoid–cercopithecoid divergence
Several lines of indirect evidence suggest that hominoids (apes and humans) and cercopithecoids (Old World monkeys) diverged around 23–25 Mya. Importantly, although this range of dates has been used as both an initial assumption and as a confirmation of results in many molecular-clock analyses, it has not been critically assessed on its own merits. In this
National Academy of Sciences.
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20. Tarsier-like locomotor specializations in the Oligocene primate Afrotarsius
Tarsiers and extinct tarsier-like primates have played a central role in views of primate phylogeny and evolution for more than a century. Because of the importance of tarsiers in so many primatological problems, there has been particular interest in questions about the origin of tarsier specializations and the biogeography of early tarsioid radiations. We r
The National Academy of Sciences.
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21. Early tertiary elephant-shrews from Egypt and the origin of the Macroscelidea.
Recent expeditions to the Fayum Depression, Egypt, have made possible the discovery of mandibles and a maxilla of a new genus and species of late Eocene elephant-shrew as well as initial evidence of the upper dentition of the early Oligocene taxon Metoldobotes. These fossils demonstrate that macroscelideans underwent a significant radiation in the Early Tert
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22. Paranasal sinus anatomy of Aegyptopithecus: Implications for hominoid origins
The East African Early Miocene apes, or proconsulids, have often been considered to be among the earliest members of the Hominoidea, as defined by the divergence of the Cercopithecoidea, but this hypothesis is only weakly supported by available fossil evidence. The ethmofrontal sinus is one of a few morphological features that may link proconsulids with late
The National Academy of Sciences.
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23. Ptolemaiida, a new order of Mammalia--with description of the cranium of Ptolemaia grangeri.
All records of the exotic mammalian family Ptolemaiidae are known from 182 m of section in the lower to middle parts of the upper Eocene and lower Oligocene Jebel Qatrani Formation, Fayum Depression, Egypt. Previous tentative assignments of ptolemaiid affinity have suggested that these animals are allied with the primitive suborder Pantolesta (currently plac
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24. Revised geochronology of the Casamayoran South American Land Mammal Age: Climatic and biotic implications
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
The National Academy of Sciences.