Jurassic bivalve biogeography

Paleobiology ◽  
1977 ◽  
Vol 3 (1) ◽  
pp. 58-73 ◽  
Author(s):  
A. Hallam
Keyword(s):  
Sea Level ◽  
Wide Distribution ◽  
Lower Jurassic ◽  
Taxonomic Composition ◽  
Extinction Rate ◽  
Ecological Groups ◽  
Sharp Rise ◽  
Extinction Rates ◽  
Endemic Genera ◽  
The Relationship

An analysis of the geographic and stratigraphic distribution of nearly 200 Jurassic bivalve genera leads to a number of new discoveries. Similarities between regions reached a maximum in the middle of the period, while the percentage of endemism correspondingly decreased. Diversity increased through the Lower Jurassic to a level which remained more or less stable from Middle Jurassic times onwards, while the origination rate shows the opposite trend. Extinction rate increased early in the period to a maximum in the Pliensbachian and fell thereafter to a low value until the Tithonian, which is marked by a sharp rise. The overall taxonomic composition of the fauna in terms of orders remained substantially stable throughout the period. The relationship with facies is discussed and three major ecological groups distinguished: marginal marine (euryhaline), shallow neritic and deep neritic. Certain pterioids have a very wide distribution and the order as a whole has a significantly higher proportion of cosmopolitan to endemic genera than any other order; the hippuritoids and trigonioids have the highest proportion of endemics. Five faunal provinces are distinguished, and the dominant control on distribution considered to be sea level. Times of high sea level were marked by widespread distribution of taxa and low endemism. High extinction rates were provoked both by regression (in the Tithonian) and by a sharp rise of sea level in the Toarcian, marked by the widespread onset of anaerobic or near-anaerobic conditions in many epicontinental seas. Some latitudinal control is recognised, notably for the hippuritoids and other stenotopic thick-shelled genera, which are confined to low latitudes.

Early Jurassic palaeopolar marine reptiles of Siberia

2020 ◽  
pp. 1-18
Author(s):  
Nikolay G. Zverkov ◽  
Dmitry V. Grigoriev ◽  
Igor G. Danilov
Keyword(s):  
Indirect Evidence ◽  
Wide Distribution ◽  
Lower Jurassic ◽  
Taxonomic Composition ◽  
Polar Night ◽  
Marine Reptiles ◽  
Polar Environment ◽  
Seasonal Migrations ◽  
Low Latitudes ◽  
Marine Reptile

Abstract Marine reptile occurrences are rare in the Lower Jurassic Series outside of Europe. Here we describe diverse marine reptile faunas from the Lower Jurassic Series (Pliensbachian and Toarcian stages, including the Toarcian–Aalenian boundary interval) of Eastern Siberia. The taxonomic composition of Toarcian marine reptile assemblages of Siberia highlight their cosmopolitan nature, with the presence of taxa previously known nearly exclusively from coeval strata of Europe, such as ichthyosaurians Temnodontosaurus and Stenopterygius, microcleidid plesiosaurians (including the genus Microcleidus), rhomaleosaurids and basal pliosaurids. The palaeogeographic reconstruction places these faunas to the palaeopolar region, north of the 80th northern parallel and up to the palaeo north pole (upper value within the 95% confidence interval for some of the localities). The materials include remains of both mature and juvenile (or even infant, judging by their very small size and poor ossification) animals, indicating a possibility that these polar seas may serve as a breeding area. The diversity and abundance of plesiosaurians and ichthyosaurians, along with a lack of thalattosuchian remains (considering their wide distribution elsewhere at low latitudes), is an additional argument that plesiosaurians and neoichthyosaurians were able to live and reproduce in a polar environment. There is no certainty whether these animals lived in polar seas permanently, or whether they were taking seasonal migrations. However, given the polar night conditions at high latitudes, the latter seems more plausible, and both these scenarios are further indirect evidence that these groups likely had a high metabolism.

Radiations and extinctions in relation to environmental change in the marine Lower Jurassic of northwest Europe

Paleobiology ◽  
1987 ◽  
Vol 13 (2) ◽  
pp. 152-168 ◽  
Author(s):  
A. Hallam
Keyword(s):  
Sea Level ◽  
Mass Extinction ◽  
Lower Jurassic ◽  
The Other ◽  
High Rate ◽  
Extinction Rate ◽  
Habitat Area ◽  
Northwest Europe ◽  
Mass Extinction Event ◽  
Neritic Habitat

A diversity and turnover analysis has been undertaken for a number of invertebrate groups in the Liassic of northwest Europe. There is a more or less steady rise in diversity from the early Hettangian through to the Pliensbachian, followed by a marked decline into the early Toarcian, after which it tends once more to increase. Ammonites stand out from the other invertebrates as having had an exceptionally high rate of turnover, with very short species durations.Increase of neritic habitat area due to rise of sea level, and recolonization following the end-Triassic mass extinction event appear to be the promoters of diversity increase or radiation. Severe reductions of neritic habitat area with associated environmental deterioration, related either to episodic marine regressions or spreads of anoxic bottom waters, and bound up respectively with sea-level fall and rise, are seen as the prime factors responsible for increase of extinction rate. While the environmentally sensitive ammonites were affected by even minor regressions, the other, more eurytopic groups were evidently more resistant to these. The only event that warrants the term mass extinction, affecting nearly all the benthos and nekton but not the plankton, correlates precisely with the early Toarcian anoxic event. Several episodes can be recognized of migrations of organisms into Europe following extinctions.

A RESSIGNIFICAÇÃO DA POBREZA MUNDIAL: NOVAS FORMAS DE TRATAMENTO

2017 ◽  
Vol 18 (1) ◽  
pp. 04
Author(s):  
Tatiani De Azevedo Lobo ◽  
Marli M. Moraes Da Costa
Keyword(s):  
Social Indicators ◽  
Academic Research ◽  
Specific Treatment ◽  
Capital Social ◽  
The South ◽  
Sharp Rise ◽  
Contemporary Debate ◽  
The World ◽  
Relationship Network ◽  
The Relationship

Resumo: O presente ensaio busca apresentar e fomentar algumas questões pertinentes ao debate contemporâneo sobre a pobreza, demonstrando a importância do tema no cenário mundial. Para tanto, inicialmente discorre-se sobre a construção histórico-social da pobreza e suas características contemporâneas. Com efeito, aponta-se a limitação dos fatores tradicionalmente apresentados como causadores da pobreza, como cultura, genética, geografia etc. Além disso, apresentam-se as formas atuais de monitorar o fenômeno, como o coeficiente de Gini e o IDH. Posteriormente, aborda-se a distribuição mundial da pobreza. Nesse ponto, colaciona-se que a pobreza é um problema mundial. No entanto, é perceptível que o Sul ainda concentra maior número de indivíduos pobres do que o Norte. Na esteira dos últimos dados da pesquisa realizada pelas Nações Unidas, houve uma nítida ascensão do Sul, especialmente nos indicadores sociais ligados à educação. A seguir, trata-se do capital social e da Teoria das Capacidades, apresentando-se novas abordagens da pobreza. Assim, o capital social trata de uma ideia utilizada para verificar a rede de relacionamento dos indivíduos. Já a Teoria das Capacidades está ligada com a ideia de oportunidade da liberdade. Por fim, estuda-se as políticas públicas, bem como seu aspecto fragmentário. Conclui-se, assim, sobre a necessidade de implementação de políticas públicas elaboradas sob a égide de novos paradigmas, a fim de possibilitar o tratamento específico do fenômeno da pobreza, conforme as peculiaridades de cada local. Para tanto foi utilizado neste trabalho o método de abordagem hipotético-dedutivo, o método de procedimento monográfico e a técnica de pesquisa, operacionalizados por meio do emprego de vasta pesquisa bibliográfica. Abstract: This essay seeks to provide and foster some relevant to the contemporary debate on poverty issues, demonstrating the importance of the issue on the world stage. For this purpose, initially spoke about the historical and social construction of poverty and its contemporary features. Indeed, he pointed out the limitation of the factors traditionally presented as the cause of poverty, as a culture, genetics, geography, etc. Furthermore, we presented the current ways of monitoring the phenomenon, such as the Gini coefficient and the HDI. Subsequently addressed the global distribution of poverty. At this point, if collated that poverty is a worldwide problem. However, it is apparent that the South still more concentrated than the poor North individuals. In the wake of recent data from research conducted by the United Nations, there was a sharp rise in the South, especially in social indicators related to education. Next, we treated the capital and the Theory of Capabilities, presenting new approaches to poverty. Thus, social capital is an idea used to verify the relationship network of individuals. Already Capabilities Theory is linked with the idea of freedom of opportunity. Finally, we studied public policy, as well as its fragmentary appearance. Thus, it is concluded on the need to implement public policies prepared under the aegis of new paradigms to enable specific treatment of the phenomenon of poverty, according to the peculiarities of each site. For that was used in this work the method of hypothetical-deductive approach, the method of procedure and the monographic research technique, operationalized through the use of extensive academic research.

scholarly journals Current extinction rate in European freshwater gastropods greatly exceeds that of the late Cretaceous mass extinction

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Thomas A. Neubauer ◽  
Torsten Hauffe ◽  
Daniele Silvestro ◽  
Jens Schauer ◽  
Dietrich Kadolsky ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Recovery Period ◽  
Freshwater Ecosystems ◽  
Extinction Rate ◽  
Freshwater Gastropods ◽  
Extinction Rates ◽  
Freshwater Biota ◽  
Order Of Magnitude ◽  
To Come ◽  
Mass Extinction Event

AbstractThe Cretaceous–Paleogene mass extinction event 66 million years ago eradicated three quarters of marine and terrestrial species globally. However, previous studies based on vertebrates suggest that freshwater biota were much less affected. Here we assemble a time series of European freshwater gastropod species occurrences and inferred extinction rates covering the past 200 million years. We find that extinction rates increased by more than one order of magnitude during the Cretaceous–Paleogene mass extinction, which resulted in the extinction of 92.5% of all species. The extinction phase lasted 5.4 million years and was followed by a recovery period of 6.9 million years. However, present extinction rates in European freshwater gastropods are three orders of magnitude higher than even these revised estimates for the Cretaceous–Paleogene mass extinction. Our results indicate that, unless substantial conservation effort is directed to freshwater ecosystems, the present extinction crisis will have a severe impact to freshwater biota for millions of years to come.

Carboniferous-Triassic gastropod diversity patterns and the Permo-Triassic mass extinction

Paleobiology ◽  
1990 ◽  
Vol 16 (2) ◽  
pp. 187-203 ◽  
Author(s):  
Douglas H. Erwin
Keyword(s):  
Mass Extinction ◽  
Detrended Correspondence Analysis ◽  
Taxonomic Composition ◽  
Late Paleozoic ◽  
Lower Permian ◽  
Two Phase ◽  
Environmental Distribution ◽  
Extinction Rates ◽  
History Of ◽  
Permian Mass Extinction

Paleozoic and post-Paleozoic marine faunas are strikingly different in composition. Paleozoic marine gastropods may be divided into archaic and modern groups based on taxonomic composition, ecological role, and morphology. Paleozoic assemblages were dominated by pleurotomariids (Eotomariidae and Phymatopleuridae), the Pseudozygopleuridae, and, to a lesser extent, the Euomphalidae, while Triassic assemblages were dominated by the Trochiina, Amberleyacea, and new groups of Loxonematoidea and Pleurotomariina. Several new groups of caenogastropods appeared as well. Yet the importance of the end-Permian mass extinction in generating these changes has been questioned. As part of a study of the diversity history of upper Paleozoic and Triassic gastropods, to test the extent to which taxonomic and morphologic trends established in the late Paleozoic are continued after the extinction, and to determine the patterns of selectivity operating during the extinction, I assembled generic and morphologic diversity data for 396 genera in 75 families from the Famennian through the Norian stages. Within this interval, gastropod genera underwent an adaptive radiation during the Visean and Namurian, largely of pleurotomariids, a subsequent period of dynamic stability through the Leonardian, a broad-based decline during the end-Permian mass extinction, and a two-phase post-extinction rebound during the Triassic. The patterns of generic diversity within superfamily-level clades were analyzed using Q-mode factor analysis and detrended correspondence analysis.The results demonstrate that taxonomic affinity, previous clade history, generic age, and gross morphology did not determine survival probability of genera during the end-Permian extinction, with the exception of the bellerophontids, nor did increasing diversity within clades or expansion of particular morphologies prior to the extinction facilitate survival during the extinction or success after it. The pleurotomariids diversified during the Lower Permian, but were heavily hit by the extinction. Similarly, trochiform and turriculate morphologies, among those which Vermeij (1987) has identified as having increased predation resistance, were expanding in the late Paleozoic, but suffered similar extinction rates to other nondiversifying clades. Survival was a consequence of broad geographic and environmental distribution, as was the case during background periods.

scholarly journals Macromycetes in the forest communities of the Jodły Łaskie nature reserve (Central Poland)

2014 ◽  
Vol 30 (1) ◽  
pp. 3-26
Author(s):  
Izabela Kałucka
Keyword(s):  
Nature Reserve ◽  
Habitat Type ◽  
Considerable Proportion ◽  
Ecological Groups ◽  
Forest Communities ◽  
Central Poland ◽  
The Relationship

The analysis of macromycetes against the background of forest communities is presented in the paper. The relationship between the mycoflora and the exploited habitat - type of phylocoenosis, stand composition, type of substrate, humidity - has been determined referring to ecological groups of fungi. Communities with considerable proportion of fir-tree in stand were particularly taken into consideration.

scholarly journals The academic precariat post-COVID-19

2021 ◽  
Author(s):  
Aidan Cornelius-Bell ◽  
Piper A. Bell
Keyword(s):  
Doctoral Students ◽  
Personal Experience ◽  
Research Literature ◽  
Corporate University ◽  
Late Capitalism ◽  
Sharp Rise ◽  
Doctoral Studies ◽  
Health Crisis ◽  
Academic Employment ◽  
The Relationship

The nature of work has changed, in accelerated late-capitalism and as a result of the COVID-19 global health crisis. For academics, casualised and precarious, the sweeping institutional changes of contemporary neoliberal universities, the sharp rise in managerialism, and the political power plays of universities have created further untenable spaces for work and study. In this article we explore the relationship between doctoral studies, precarious academic employment, the pandemic, and the disproportionate effects of the changes in higher education on women. Through exploration of personal experience, as precarious academic workers, researchers, and doctoral students, we provide parallels to research literature across pandemic and post-COVID literature. We provide practical suggestions for the corporate university, to rebuild its catastrophically collapsing systems, and re-centre doctoral students in mentorship as the new future of universities in Australia, and around the world.

Do You Drink Glacier Water? Probably

2021 ◽  
pp. 87-107
Author(s):  
Jorge Daniel Taillant
Keyword(s):  
Water Supply ◽  
Sea Level ◽  
Human Consumption ◽  
Mountain Glaciers ◽  
Glacier Melt ◽  
Prolonged Drought ◽  
The Relationship ◽  
At Home

This chapter discusses the relationship between glacier melt, sea level, and water supply and the relationship between the water we drink at home and use for agriculture to mountain glaciers. It describes the Earth’s freshwater supply and its various compositions and locations. It gives concrete examples of different sized glaciers and their relative freshwater contribution to nearby populations. It reviews the freshwater basin storage and regulation role that glaciers play in ecosystems and the importance of glaciers as sources of freshwater for human consumption and agriculture during warm and dry months as well as during prolonged drought periods.

scholarly journals The dynamics underlying avian extinction trajectories forecast a wave of extinctions

2019 ◽  
Vol 15 (12) ◽  
pp. 20190633 ◽  
Author(s):  
Melanie J. Monroe ◽  
Stuart H. M. Butchart ◽  
Arne O. Mooers ◽  
Folmer Bokma
Keyword(s):  
Extinction Risk ◽  
Population Decline ◽  
Bird Species ◽  
Iucn Red List ◽  
Red List ◽  
Extinction Rate ◽  
Critically Endangered Species ◽  
Extinction Rates ◽  
Historical Times ◽  
Risk Categories

Population decline is a process, yet estimates of current extinction rates often consider just the final step of that process by counting numbers of species lost in historical times. This neglects the increased extinction risk that affects a large proportion of species, and consequently underestimates the effective extinction rate. Here, we model observed trajectories through IUCN Red List extinction risk categories for all bird species globally over 28 years, and estimate an overall effective extinction rate of 2.17 × 10 −4 /species/year. This is six times higher than the rate of outright extinction since 1500, as a consequence of the large number of species whose status is deteriorating. We very conservatively estimate that global conservation efforts have reduced the effective extinction rate by 40%, but mostly through preventing critically endangered species from going extinct rather than by preventing species at low risk from moving into higher-risk categories. Our findings suggest that extinction risk in birds is accumulating much more than previously appreciated, but would be even greater without conservation efforts.

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