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| Woelfli,Willy; Baltensperger,Walter. |
| Remains of mammoths in Arctic East Siberia, where there is not sufficient sunlight over the year for the growth of the plants on which these animals feed, indicate that the latitude of this region was lower before the end of the Pleistocene than now. Reconstructing this geographic pole shift, we introduce a massive object, which moved in an extremely eccentric orbit and was hot from tidal work and solar radiation. Evaporation produced a disk-shaped cloud of ions around the Sun. This cloud partially shielded the solar radiation, producing the cold and warm periods characterizing the Pleistocene. The shielding depends on the inclination of Earth's orbit, which has a period of 100. 000 years. The cloud builds up to a point where inelastic particle collisions... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Ice age; Pole shift; Interplanetary cloud; Mass extinction. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000200001 |
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| Nahum,Laila Alves; Pereira,Sérgio Luiz; Campos Fernandes,Flora Maria de; Russo Matioli,Sergio; Wajntal,Anita. |
| Partial cytochrome b and 12S rDNA mitochondrial DNA sequences of eight representatives of the Ramphastidae family were analyzed. We applied the linearized tree method to identify sequences evolving at similar rates and estimated the divergence times among some of the taxa analyzed. After excluding Ramphastos tucanus and Capito dayi from our data set, the remaining taxa presented a constant rate of DNA substitution, and branch lengths could be re-estimated with a clock constraint using the maximum likelihood method. Branch lengths were calibrated assuming that Galliformes and Piciformes split around 100 million years ago (mya). Our results indicate that Ramphastinae, and probably Capitoninae, diverged from other Piciformes in the Late Cretaceous (~82 mya),... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Divergence times; K/T; Mass extinction; Cytochrome b; 12S rDNA; Paleogeography; Phylogeny. |
| Ano: 2003 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572003000400003 |
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| BRUSATTE,STEPHEN L.; CANDEIRO,CARLOS R.A.; SIMBRAS,FELIPE M.. |
| ABSTRACT The non-avian dinosaurs died out at the end of the Cretaceous, ~66 million years ago, after an asteroid impact. The prevailing hypothesis is that the effects of the impact suddenly killed the dinosaurs, but the poor fossil record of latest Cretaceous (Campanian-Maastrichtian) dinosaurs from outside Laurasia (and even more particularly, North America) makes it difficult to test specific extinction scenarios. Over the past few decades, a wealth of new discoveries from the Bauru Group of Brazil has revealed a unique window into the evolution of terminal Cretaceous dinosaurs from the southern continents. We review this record and demonstrate that there was a diversity of dinosaurs, of varying body sizes, diets, and ecological roles, that survived to... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Brazil; Cretaceous; Dinosaur; Gondwana; K-Pg boundary; Mass extinction. |
| Ano: 2017 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652017000401465 |
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