Search results for " extinction"
showing 10 items of 91 documents
Mercury contents and isotope ratios from diverse depositional environments across the Triassic–Jurassic Boundary: Towards a more robust mercury proxy…
2021
Abstract Mercury is gaining prominence as a proxy for large igneous province (LIP) volcanism in the sedimentary record. Despite temporal overlap between some mass extinctions and LIPs, the precise timing of magmatism relative to major ecological and environmental change is difficult to untangle, especially in marine settings. Changes in the relative contents of Hg in sedimentary rocks through time, or ‘Hg anomalies’, can help resolve the timing of LIP activity and marine extinctions. However, major questions remain unanswered about the fidelity of Hg as a proxy for LIP magmatism. In particular, depositional (e.g., redox) and post-depositional (e.g., oxidative weathering) processes can affec…
Positive Sulfate Sulfur Isotope Excursion Indicates Large-Scale Pyrite Burial and Marine Anoxia during the End–Triassic Mass Extinction
2020
The late Rhaetian–early Hettangian transition is characterised by the emplacement of Central Atlantic magmatic province and associated climatic effects, coincident with a severe biotic crisis (~201.5 Ma). The oxygen deficiency in the ocean realm is possibly linked to this significant loss in marine biodiversity. However, direct evidence of contemporaneous development of marine anoxia on a global scale has been lacking and the relationship between oxygen and extinction is unclear. Here we report carbonate-associated sulfate δ34S data from three sections across the Late Triassic–Early Jurassic transition. We find synchronous large positive δ34S shifts with a magnitude of >10‰ in the latest…
Bivalves and evolutionary resilience: Old skills and new strategies to recover from the P/T and T/J extinction events
2011
Diversity dynamics among bivalves during the Triassic and Early Jurassic provides the opportunity to analyse the recovery patterns after two mass extinctions: Permian/Triassic and Triassic/Jurassic (T/J). The results presented here are based on a newly compiled worldwide genus-level database and are contrasted to the main morphological characters of the different taxonomical (orders and their constituent families and genera) and ecological groups. Many of such morphological characters are innovations appearing during the time span considered. Diversity and evolutionary rates were assessed and compared between these groups. During the Early Triassic there was a slow recovery, dominated by ep…
David Malcolm Raup (1933-2015) at the starting point of a new paradigm for Palaeontology
2020
This is a tribute to the late David Malcolm Raup, one of the major palaeontologists of the second half of the 20 th century. In addition, it is a critical review of his outstanding contributions, mainly in the field of theoretical palaeontology: quantitative modelling, the introduction of probabilistic methods in palaeontology, as well as his great imagination to use techniques from other fields, such as insurance actuary. After a general outline of his youth, I present a general depiction of the main topics of his research as a palaeobiologist: morphology, the structure of the fossil record, evolution, and extinction. He covered areas ranging from the theoretical morphology of coiled shell…
Timing and selectivity of the Late Mississippian mass extinction of brachiopod genera from the Central Appalachian Basin
2008
The seventh largest mass extinction of the Phanerozoic Era occurred in the Late Mississippian and coincided with the onset of the late Paleozoic ice age. Analyses of brachiopod genera from Mississippian strata of the Central Appalachian Basin reveal that the regional expression of the mass extinction occurred after the development of high-amplitude glacioeustasy by several million years and occurred instead during low-latitude cooling and the expansion of glaciation near the Mississippian-Pennsylvanian boundary. The Late Mississippian mass extinction was even more severe for genera in the Central Appalachian Basin than global metrics would predict; in addition to the genera of this basin th…
Local Extinction of Dragonfly and Damselfly Populations in Low- and High-Quality Habitat Patches
2010
Understanding the risk of extinction of a single population is an important problem in both theoretical and applied ecology. Local extinction risk depends on several factors, including population size, demographic or environmental stochasticity, natural catastrophe, or the loss of genetic diversity. The probability of local extinction may also be higher in low-quality sink habitats than in high-quality source habitats. We tested this hypothesis by comparing local extinction rates of 15 species of Odonata (dragonflies and damselflies) between 1930-1975 and 1995-2003 in central Finland. Local extinction rates were higher in low-quality than in high-quality habitats. Nevertheless, for the thre…
Challenging Darwin: Evolution of Triassic Conodonts and Their Struggle for Life in a Changing World
2017
Abstract The phylogeny and distribution of Triassic conodonts reveal many aspects of their natural history. Conodonts incorporate the morphologic response to temperature as well as to eustatic cycles. Speciation, radiation, and extinction are not fortuitous and evolution uses heterochrony (progenesis and neoteny) in response to stress-generating events. Proteromorphosis (reappearance of ancestral morphs) and paedomorphosis (retention of juvenile traits) is a reaction to sublethal environmental stress. This often follows radiation of fully developed forms in the recovery stage after extinction that timely matches transgressions. Evolutionary retrogradation (neoteny) during eustatic high stan…
Disturbance-induced emigration: an overlooked mechanism that reduces metapopulation extinction risk.
2021
Emigration propensity (i.e., the tendency to leave undisturbed patches) is a key life-history trait of organisms in metapopulations with local extinctions and colonizations. Metapopulation models of dispersal evolution typically assume that patch disturbance kills all individuals within the patch, thus causing local extinction. However, individuals may instead be able to leave a patch when it is disturbed, either by fleeing before being killed or simply because the disturbance destroys the patch without causing mortality. This scenario may pertain to a wide range of organisms from horizontally transmitted symbionts, to aquatic insects inhabiting temporary ponds, to vertebrates living in fra…
Non-breeding waterbirds benefit from protected areas when adjusting their distribution to climate warming
2021
AbstractClimate warming is driving changes in species distributions, although many species show a so-called climatic debt, where their range shifts lag behind the fast shift in temperature isoclines. Protected areas (PAs) may impact the rate of distribution changes both positively and negatively. At the cold edges of species distributions, PAs can facilitate species distribution changes by increasing the colonization required for distribution change. At the warm edges, PAs can mitigate the loss of species, by reducing the local extinction of vulnerable species. To assess the importance of PAs to affect species distribution change, we evaluated the changes in a non-breeding waterbird communi…
Has palaeontology answers for some current environmental problems?
2021
History as an irreversible process has no role from a uniformitarian point of view in geology and palaeobiology. Contingency is another trait of history and particle palaeontology has its foundation on such principles. However, new approaches in physics and the theory of systems point out the need to consider a time arrow. Moreover, chance and necessity are interwoven in synergetics and self-organization theory and there may be some possibility of prediction. The global biota has a history resulting from a process of self-organization. A rich fossil record was produced during the Phanerozoic times and this fossil record shows us how life overcame several important crisis. A clear understand…