نتایج جستجو برای: oligocene

تعداد نتایج: 2183  

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2001
E L Simons

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 regarded by some as the sister group to al...

2015
Felix G. Marx Cheng-Hsiu Tsai R. Ewan Fordyce

Archaic toothed mysticetes represent the evolutionary transition from raptorial to bulk filter feeding in baleen whales. Aetiocetids, in particular, preserve an intermediate morphological stage in which teeth functioned alongside a precursor of baleen, the hallmark of all modern mysticetes. To date, however, aetiocetids are almost exclusively Late Oligocene and coeval with both other toothed my...

2014
Jing-Yu Wu Su-Ting Ding Qi-Jia Li Zhen-Rui Zhao Bai-Nian Sun

Platycladus Spach is native to Central China, but its natural occurrences are very difficult to establish. According to molecular phylogenetic data, this genus might have originated since the Oligocene, but no fossil record has been reported. Here, we describe eight foliage branches from the upper Miocene in western Yunnan, Southwest China as a new species, P. yunnanensis sp. nov., which is cha...

1999
James C. Zachos Bradley N. Opdyke Terrence M. Quinn Charles E. Jones Alex N. Halliday

Stable and radiogenic isotopic and sedimentological data from sub-Antarctic deep sea sediment cores reveal a temporal link between changes in seawater SrrSr ratios and major episodes of late Eocene–early Oligocene climate change. The SrrSr records show two major inflections, one at 38–39 Ma near the middlerlate Eocene boundary, followed by another at 33.4 Ma. Similarly, the oxygen isotope, ice-...

2000
FRED RÖGL

Paleogeographical considerations on the development of the Paratethys and the Mediterranean during Oligocene and Miocene are presented in twelve time-slices. Plate tectonic activities and the collision of India with Asia caused the destruction of the Western Tethys Ocean in the Late Eocene. The Mediterranean and the intracontinental Paratethys basins came into existence as new marine realms. In...

2015
T. K. Ambrose K. P. Larson C. Guilmette J. M. Cottle S. Rai

Integrated pseudosection modeling and monazite petrochronology of paragneiss from the Kanchenjunga region of northeastern Nepal reveal the presence of cryptic tectonometamorphic discontinuities within the Himalayan metamorphic core. These new data outline a series of thrust-sense structures that juxtapose rocks that generally record a protracted history of early Eocene to latest Oligocene–early...

2007
E. E. Greenhalgh N. J. Kusznir

[1] Satellite gravity inversion incorporating a lithosphere thermal gravity correction has been used to map crustal thickness and lithosphere thinning factor for the NE Atlantic. Predicted oceanic crustal thicknesses in the Norwegian Basin are between 4 and 7 km on the extinct Aegir Ridge, increasing to 9 – 14 km at the margins, consistent with volcanic margin continental breakup at the end of ...

Journal: :Proceedings. Biological sciences 2012
Gudrun Kadereit David Ackerly Michael D Pirie

C(4) photosynthesis is a fascinating example of parallel evolution of a complex trait involving multiple genetic, biochemical and anatomical changes. It is seen as an adaptation to deleteriously high levels of photorespiration. The current scenario for C(4) evolution inferred from grasses is that it originated subsequent to the Oligocene decline in CO(2) levels, is promoted in open habitats, ac...

2016
Peng Zhang Hong Ao Mark J. Dekkers Yongxiang Li Zhisheng An

A large number of terrestrial mammalian fossils were reported in the well-exposed Paleogene and Neogene fluvio-lacustrine strata in Western China. Their accurate ages are crucial to understand the mammalian and environmental evolution associated with the step-wise uplift of the Tibetan Plateau. At present their ages are surprisingly poorly constrained. Here, we present a high-resolution magneto...

2017
Sylvain Richoz Andre Baldermann Andreas Frauwallner Mathias Harzhauser Gudrun Daxner-Höck Dietmar Klammer Werner E Piller

The Valley of Lakes is approximately a 500-km elongate depression in Central Mongolia, where Eocene to Miocene continental sediments are long known for their outstanding fossil richness. The palaeontological record of this region is an exceptional witness for the evolution of mammalian communities during the Cenozoic global cooling and regional aridification. In order to precisely elucidate the...

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