Sökning: "K-Pg boundary"

Hittade 3 avhandlingar innehållade orden K-Pg boundary.

  1. 1. Changes in ocean geochemistry across the K-Pg boundary interval

    Författare :Tjördis Störling; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; K-Pg boundary; Paleocene; stable silicon isotopes; sponge spicules; radiolaria; Cerithium Limestone;

    Sammanfattning : The Cretaceous - Paleogene boundary (K-Pg, 66 Ma) was a time interval with dramatic changes in the Earth’s climate and the ocean environment. It was characterized by severe disruptions of marine biogeochemical cycles due to a meteorite impact during a time of active volcanism. LÄS MER

  3. 2. 100 million years of shark macroevolution : A morphometric dive into tooth shape diversity

    Författare :Mohamad Bazzi; Per Ahlberg; Matt Friedman; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sharks; Macroevolution; Extinction recovery dynamics; Geometric Morphometrics; Morphospace-Disparity Framework; Teeth; Biology with specialization in Evolutionary Organismal Biology; Biologi med inriktning mot evolutionär organismbiologi;

    Sammanfattning : Few vertebrate clades exhibit the evolutionary longevity and versatility of sharks, which constitute nearly half of all current chondrichthyan biodiversity and represent an ecological diversity of mid-to-apex trophic-level predators in both marine and freshwater environments. The rich fossil record of shark teeth from Mesozoic and Cenozoic rocks also makes the group amenable to large-scale quantitative analyses. LÄS MER

  4. 3. Evolutionary studies of the Gnetales

    Författare :Chen Hou; Catarina Rydin; Richard Saunders; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; växtsystematik; Plant Systematics;

    Sammanfattning : The Gnetales consist of three distinct genera, Ephedra, Gnetum and Welwitschia with considerable divergence among them regarding morphological, ecological and molecular characters. A longstanding debate of the similarity between the Gnetales and angiosperms and the unresolved seed plant phylogeny intrigues plant scientists to further investigate the evolutionary history of the Gnetales. LÄS MER