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Reimold W.U.,Leibniz Institute for Evolution and Biodiversity Science | Reimold W.U.,Humboldt University of Berlin | Koeberl C.,University of Vienna
Journal of African Earth Sciences | Year: 2014

More than 50. years of space and planetary exploration and concomitant studies of terrestrial impact structures have demonstrated that impact cratering has been a fundamental process - an essential part of planetary evolution - ever since the beginning of accretion and has played a major role in planetary evolution throughout the solar system and beyond. This not only pertains to the development of the planets but to evolution of life as well. The terrestrial impact record represents only a small fraction of the bombardment history that Earth experienced throughout its evolution. While remote sensing investigations of planetary surfaces provide essential information about surface evolution and surface processes, they do not provide the information required for understanding the ultra-high strain rate, high-pressure, and high-temperature impact process. Thus, hands-on investigations of rocks from terrestrial impact craters, shock experimentation for pressure and temperature calibration of impact-related deformation of rocks and minerals, as well as parameter studies pertaining to the physics and chemistry of cratering and ejecta formation and emplacement, and laboratory studies of impact-generated lithologies are mandatory tools. These, together with numerical modeling analysis of impact physics, form the backbone of impact cratering studies.Here, we review the current status of knowledge about impact cratering - and provide a detailed account of the African impact record, which has been expanded vastly since a first overview was published in 1994. No less than 19 confirmed impact structures, and one shatter cone occurrence without related impact crater are now known from Africa. In addition, a number of impact glass, tektite and spherule layer occurrences are known. The 49 sites with proposed, but not yet confirmed, possible impact structures contain at least a considerable number of structures that, from available information, hold the promise to be able to expand the African impact record drastically - provided the political conditions for safe ground-truthing will become available. The fact that 28 structures have also been shown to date NOT to be of impact origin further underpins the strong interest in impact in Africa. We hope that this review stimulates the education of students about impact cratering and the fundamental importance of this process for Earth - both for its biological and geological evolution. This work may provide a reference volume for those workers who would like to search for impact craters and their ejecta in Africa. © 2014 Elsevier Ltd. Source

Gomez B.,CNRS Geological Laboratory of Lyon: earth, planets and environment | Daviero-Gomez V.,CNRS Geological Laboratory of Lyon: earth, planets and environment | Coiffard C.,Leibniz Institute for Evolution and Biodiversity Science | Martin-Closas C.,University of Barcelona | Dilcher D.L.,Indiana University Bloomington
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

The early diversification of angiosperms in diverse ecological niches is poorly understood. Some have proposed an origin in a darkened forest habitat and others an open aquatic or near aquatic habitat. The research presented here centers on Montsechia vidalii, first recovered from lithographic limestone deposits in the Pyrenees of Spain more than 100 y ago. This fossil material has been poorly understood and misinterpreted in the past. Now, based upon the study of more than 1,000 carefully prepared specimens, a detailed analysis of Montsechia is presented. The morphology and anatomy of the plant, including aspects of its reproduction, suggest that Montsechia is sister to Ceratophyllum (whenever cladistic analyses are made with or without a backbone). Montsechia was an aquatic angiosperm living and reproducing below the surface of the water, similar to Ceratophyllum. Montsechia is Barremian in age, raising questions about the very early divergence of the Ceratophyllum clade compared with its position as sister to eudicots in many cladistic analyses. Lower Cretaceous aquatic angiosperms, such as Archaefructus and Montsechia, open the possibility that aquatic plants were locally common at a very early stage of angiosperm evolution and that aquatic habitats may have played a major role in the diversification of some early angiosperm lineages. © 2015, National Academy of Sciences. All rights reserved. Source

Coleman C.O.,Leibniz Institute for Evolution and Biodiversity Science
Journal of Crustacean Biology | Year: 2015

The term "taxonomic impediment" is widely used in the biodiversity literature. The taxonomic impediment consists of several problems: the incomplete knowledge of the largely unknown global biodiversity, the insufficient number of experts and their unbalanced distribution across the globe and the taxonomic infrastructures that are not meeting the demands yet. It is difficult to examine how severe the problem in the development of taxonomic knowledge is, because there might be big taxonomic gaps in knowledge in some groups, like many invertebrates, but small in some vertebrate taxa. As an example of an invertebrate taxon, the online WoRMS database was queried for amphipod crustaceans, and data for the cumulative increase of species numbers, species description rates and data from the taxonomic community were extracted. The increase of species numbers over time is strong and the species description rates are high since the 1960s. Within the group of 30 most productive amphipod taxonomists during the past 15 years, 9 are retired, 2 are on temporary contracts, 1 is a freelancer, 8 stopped working on amphipods leaving 9 out of 30 permanently employed. There is a strong geographical bias with 21 of the 30 taxonomists originating from Australia, Europe, North-America and Japan especially within the group of highest productivity. The taxonomic effort of amphipodologists was compared with the situation in Cumacea and Mysidacea. © 2015 by The Crustacean Society. Published by Brill NV, Leiden. Source

Wunnemann K.,Leibniz Institute for Evolution and Biodiversity Science | Weiss R.,Virginia Polytechnic Institute and State University
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2015

When a cosmic object strikes the Earth, it most probably falls into an ocean. Depending on the impact energy and the depth of the ocean, a large amount of water is displaced, forming a temporary crater in the water column. Large tsunami-like waves originate from the collapse of the cavity in the water and the ejecta splash. Because of the far-reaching destructive consequences of such waves, an oceanic impact has been suggested to be more severe than a similarsized impact on land; in other words, oceanic impacts may punch over their weight. This review paper summarizes the process of impact-induced wave generation and subsequent propagation, whether the wave characteristic differs from tsunamis generated by other classical mechanisms, and what methods have been applied to quantify the consequences of an oceanic impact. Finally, the impact-induced tsunami hazard will be evaluated by means of the Eltanin impact event. Copyright © 2015 The Author(s) Published by the Royal Society. Source

Dunlop J.A.,Leibniz Institute for Evolution and Biodiversity Science | De Oliveira Bernardi L.F.,Campus Universitario
Naturwissenschaften | Year: 2014

A fossil opilioacarid mite (Parasitiformes: Opilioacarida) in Burmese amber is described as ?Opilioacarus groehni sp. nov. This ca. 99 Ma record (Upper Cretaceous: Cenomanian) represents only the third fossil example of this putatively basal mite lineage, the others originating from Eocene Baltic amber (ca. 44-49 Ma). Our new record is not only the oldest record of Opilioacarida, but it is also one of the oldest examples of the entire Parasitiformes clade. The presence of Opilioacarida - potentially Opiloacarus - in the Cretaceous of SE Asia suggests that some modern genus groups were formerly more widely distributed across the northern hemisphere, raising questions about previously suggested Gondwanan origins for these mites. © 2014 Springer-Verlag Berlin Heidelberg. Source

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