نتایج جستجو برای: mass extinction

تعداد نتایج: 500636  

2003
R. Guzmán G. Östlin D. Kunth M. A. Bershady D. C. Koo M. A. Pahre

We present stellar mass measurements for a sample of 36 luminous compact blue galaxies (LCBGs) at redshifts in the flanking fields around the Hubble Deep Field–North. The technique is based on fitting a twoz p 0.4–1.2 component galaxy population model to multi-broadband photometry. Best-fit models are found to be largely independent of the assumed values for the initial mass function (IMF) and ...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2003
Rowan Lockwood

Ecological studies suggest that rare taxa are more likely to go extinct than abundant ones, but the influence of abundance on survivorship in the fossil record has received little attention. An analysis of Late Maastrichtian bivalve subgenera from the North American Coastal Plain found no evidence that survivorship is tied to abundance across the end-Cretaceous mass extinction (65 million years...

Journal: :Science 1998
D'Hondt Donaghay Zachos Luttenberg Lindinger

Differences between the carbon isotopic values of carbonates secreted by planktic and benthic organisms did not recover to stable preextinction levels for more than 3 million years after the Cretaceous-Tertiary mass extinction. These decreased differences may have resulted from a smaller proportion of marine biological production sinking to deep water in the postextinction ocean. Under this hyp...

2014
Kowiyou Yessoufou Samuel O Bamigboye Barnabas H Daru Michelle van der Bank

The recent evidence that extant cycads are not living fossils triggered a renewed search for a better understanding of their evolutionary history. In this study, we investigated the evolutionary diversification history of the genus Encephalartos, a monophyletic cycad endemic to Africa. We found an antisigmoidal pattern with a plateau and punctual explosive radiation. This pattern is typical of ...

2012
Randall B. Irmis Jessica H. Whiteside

During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects...

2017
J H F L Davies A Marzoli H Bertrand N Youbi M Ernesto U Schaltegger

The end-Triassic extinction is one of the Phanerozoic's largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earlies...

Journal: :Science 2009
Kaustuv Roy Gene Hunt David Jablonski

Evolutionary histories of species and lineages can influence their vulnerabilities to extinction, but the importance of this effect remains poorly explored for extinctions in the geologic past. When analyzed using a standardized taxonomy within a phylogenetic framework, extinction rates of marine bivalves estimated from the fossil record for the last approximately 200 million years show conserv...

Journal: :Proceedings of the Royal Society B: Biological Sciences 2008

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