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      Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction

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          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Significance

          We present a quantitative test of end-Cretaceous extinction scenarios and how these would have affected dinosaur habitats. Combining climate and ecological modeling tools, we demonstrate a substantial detrimental effect on dinosaur habitats caused by an impact winter scenario triggered by the Chicxulub asteroid. We were not able to obtain such an extinction state with several modeling scenarios of Deccan volcanism. We further show that the concomitant prolonged eruption of the Deccan traps might have acted as an ameliorating agent, buffering the negative effects on climate and global ecosystems that the asteroid impact produced at the Cretaceous–Paleogene boundary.

          Abstract

          The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO 2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.

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          Most cited references 92

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          Mass extinctions in the marine fossil record.

           D Raup,  J Sepkoski (1982)
          A new compilation of fossil data on invertebrate and vertebrate families indicates that four mass extinctions in the marine realm are statistically distinct from background extinction levels. These four occurred late in the Ordovician, Permian, Triassic, and Cretaceous periods. A fifth extinction event in the Devonian stands out from the background but is not statistically significant in these data. Background extinction rates appear to have declined since Cambrian time, which is consistent with the prediction that optimization of fitness should increase through evolutionary time.
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            The placental mammal ancestor and the post-K-Pg radiation of placentals.

            To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats). Our tree suggests that Placentalia first split into Xenarthra and Epitheria; extinct New World species are the oldest members of Afrotheria.
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              The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary.

              The Cretaceous-Paleogene boundary approximately 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.
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                Author and article information

                Journal
                Proc Natl Acad Sci U S A
                Proc. Natl. Acad. Sci. U.S.A
                pnas
                pnas
                PNAS
                Proceedings of the National Academy of Sciences of the United States of America
                National Academy of Sciences
                0027-8424
                1091-6490
                21 July 2020
                29 June 2020
                29 June 2020
                : 117
                : 29
                : 17084-17093
                Affiliations
                aDepartment of Earth Science and Engineering, Imperial College London , South Kensington, SW7 2AZ London, United Kingdom;
                bDepartment of Earth Sciences, University College London , WC1E 6BT London, United Kingdom;
                cSchool of Geographical Sciences, University of Bristol , BS8 1TH Bristol, United Kingdom
                Author notes
                2To whom correspondence may be addressed. Email: a.chiarenza15@ 123456gmail.com .

                Edited by Nils Chr. Stenseth, University of Oslo, Oslo, Norway, and approved May 21, 2020 (received for review April 1, 2020)

                Author contributions: A.A.C., A.F., P.D.M., J.V.M., and P.A.A. designed research; A.A.C., A.F., and P.D.M. performed research; D.J.L. contributed new reagents/analytic tools; A.A.C., A.F., and P.J.V. analyzed data; D.J.L., P.J.V., and J.V.M. contributed to experimental design of the GCMs; A.A.C., A.F., and P.D.M. wrote the paper; and D.J.L., P.J.V., J.V.M., and P.A.A. contributed to writing the paper.

                1A.A.C. and A.F. contributed equally to this work.

                Article
                202006087
                10.1073/pnas.2006087117
                7382232
                32601204
                Copyright © 2020 the Author(s). Published by PNAS.

                This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

                Page count
                Pages: 10
                Product
                Categories
                Biological Sciences
                Evolution
                Physical Sciences
                Earth, Atmospheric, and Planetary Sciences

                dinosauria, extinction, end-cretaceous, chicxulub, deccan

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