22 research outputs found

    How many species of fossil arachnids are there?

    Get PDF
    The species-level diversity of fossil Chelicerata is summarized for each order. 1952 valid species of fossil\ud chelicerates are currently recognized, of which 1593 are arachnids. In order of abundance they are: Araneae (979 fossil\ud species), Actinotrichida (283), Eurypterida (241), Scorpiones (111), Xiphosura (96), Trigonotarbida (71), Pseudoscorpiones\ud (38), Phalangiotarbida (30), Opiliones (25), Ricinulei (15), and Anactinotrichida (11). Other groups are represented by ten\ud fossil species or fewer. Based on published descriptions, spiders thus appear to dominate the fossil arachnid species\ud assemblage, making up a greater proportion of paleodiversity than their Recent diversity would predict. Scorpions are also\ud overrepresented, particularly in the Paleozoic, compared to their modern diversity. By contrast, groups like mites,\ud harvestmen, pseudoscorpions and solifuges are noticeably under-represented as fossils when compared to modern patterns\ud of diversity

    ARTHROPOD SEBAGAI IDE PENCIPTAAN FOTOGRAFI

    Get PDF
    Penciptaan Karya Tugas Akhir ini bertujuan untuk mengangkat hewan Arthropod sebagai objek utama dan lensa macro sebagai pendukung melalui fotografi. Arthropod (dalam bahasa latin, Arthra = ruas , buku, segmen ; podos = kaki) merupakan hewan yang memiliki ciri kaki beruas, berbuku, atau bersegmen. Segmen tersebut juga terdapat pada tubuhnya. Fotografi menjadi media yang digunakan untuk menyalurkan ide dan konsep, karya- karya foto yang diciptakan menampilkan seraingkaian visual tentang hewan arthropod. Demi tercapainya makna dan penyampaian pesannya digunakan properti sebagai pendukung dalam setiap karyanya contohnya pasir, batu,kayu dan daun-daun,dll Hewan arthropod di foto menggunakan teknik fotografi macro agar foto tampak detail dan memiliki tekstur yang menarik. Dengan penggunaan teknik fotografi macro yang benar maka akan tercipta sebuah karya yang menarik tentang arthropod tersebut, visualisasi, komposisi yang menarik dan mudah dipahami dalam penciptaan ini

    Great Canadian Lagerstätten 3. Late Ordovician Konservat-Lagerstätten in Manitoba

    Get PDF
    Konservat-Lagerstätten, deposits in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician strata. Three significant sites are known from Upper Ordovician rocks in Manitoba: at Cat Head – McBeth Point, William Lake, and Airport Cove. These sites are in two distinct sedimentary basins: the former two are in the Williston Basin, while the latter is in the Hudson Bay Basin. All three sites contain marine fossils, but each has a different assemblage that contributes a distinct piece of the diversity picture. Important groups represented at one or more of the sites include seaweeds (algae), sponges, cnidarian medusae (jellyfish), conulariids, trilobites, eurypterids, xiphosurids (horseshoe crabs), and pycnogonids (‘sea spiders’). The different biotas reflect depositional conditions at each site. Many of the fossils are unknown elsewhere in the Ordovician at the family level or higher. The province of Manitoba therefore makes a significant contribution to knowledge of Late Ordovician biodiversity.SOMMAIRELes lagerstätten de conservation, ces sédiments contenant des fossiles d’organismes à corps mou ou légèrement sclérotisés particulièrement bien conservés, sont très rares dans les strates ordoviciennes.  Trois sites d’importance sont connus dans des roches de l'Ordovicien supérieur à Cat Head, Manitoba, soit McBeth Point, William Lake et  Airport Cove.  Ces sites sont situés dans deux bassins sédimentaires distincts : les deux premiers sont situés dans le bassin de Williston, tandis que le second est situé dans le bassin de la baie d'Hudson.  Les trois sites contiennent des fossiles marins, mais chacun présente un assemblage différent, chacun montrant une composante distincte de la diversité biologique d’alors.  Les groupes les plus importants représentés, dans un ou plusieurs de ces sites, sont les algues, les éponges, les cnidarian medusae (méduses), les conularides, les trilobites, les euryptérides, xiphosurides (limules) et pycnogonides.  Les différents biotopes reflètent les conditions de dépôt de chaque site.  Nombre de ces fossiles sont inconnus ailleurs dans l'Ordovicien, au niveau de la famille ou du taxon supérieur de la classification.  Ainsi, la province du Manitoba offre-t-elle une contribution importante à la connaissance de la biodiversité de l'Ordovicien supérieur

    In memory of Alberto Mario Simonetta (1930-2021)

    Get PDF
    The polyvalent figure of Alberto Mario Simonetta (Pisa, 1930 - Florence, 2021), one of the most important exponents of Italian Zoology of the last century, is here presented with a brief biographical note, a list of the taxa he described and of those dedicated to him, and a complete list of his publications

    Selectivity in the evolution of Palaeozoic arthropod groups, with focus on mass extinctions and radiations: a phylogenetic approach

    Get PDF
    Mass extinctions are known to be extraordinary events during which the normal rules of natural selection do not apply. Evidence points to the operation of a different selective regime, one where clade-level properties are selected upon; however, it is still unclear whether survivorship rules apply across different extinction events, the consequences of differential responses in diversity and disparity during extinction events, and the factors governing subsequent recoveries. This dissertation explores these issues by studying three clades of arthropods that experience multiple extinction events, allowing for the effect of different mass extinctions on the same group to be compared utilizing phylogenetic methodology. Three phylogenies where generated, one each for Stylonurina, Eurypterina, and Aulacopleuroidea. Variations in diversity, disparity, and volatility, are compared across these clades for two extinction events: the end-Ordovician (443 Ma) and the late Devonian (385- 359 Ma). Consistent differences in how morphospace occupation changes across the end- Ordovician and late Devonian mass extinction events reveal that the underlying driving factors of individual extinction events can result in very different selective pressures, suggesting that it may not be possible to identify general survivorship rules for all mass extinctions. Ecology is revealed to be a major factor behind the responses of individual species to the late Devonian biodiversity crisis. The somewhat contradictory selective signal exhibited by the studied clades reveals how different aspects of ecology can influence diversity, disparity and volatility in different ways, each influencing aspects of clade survival and recovery in different ways. The results also demonstrate the bearing of the evolutionary history of a clade on such studies. Contingency is an important factor in determining the response of clades to mass extinctions, and only through having a firm understanding of the history of a group can such factors be appropriately accounted for

    On Paleolimulus from the Mazon Creek Konservat-Lagerstätte

    Get PDF
    Sur Paleolimulus de la Konservat-Lagerstätte de Mazon Creek. Les xiphosuridés, aussi appelés limules, incluent des chélicérates actuels dont le registre fossile remonte à l'Ordovicien. Malgré les traces de leur longue histoire évolutive, les xiphosuridés sont rarement préservés dans les assemblages fossiles en raison de leur exosquelette cuticulaire non minéralisé. Cependant, dans des circonstances exceptionnelles, une abondance de spécimens de xiphosurides fossiles a été documentée. Le Konservat-Lagerstätte de Mazon Creek, d'âge Moscovien, représente un tel dépôt de fossiles qui présente une grande abondance et diversité de xiphosuridés. Bien que relativement bien connus, les spécimens de Paleolimulus de Mazon Creek n'ont pas encore fait l'objet d'un examen taxonomique approfondi. A la lumière des efforts récents pour organiser Paleolimulus, nous revisitons ce matériel non décrit, érigeons Paleolimulus mazonensis n. sp., et présentons une analyse phylogénétique qui place P. mazonensis n. sp. comme un taxon frère de P. signata (Beecher, 1904). La paléoécologie et l'ontogenèse possible de P. mazonensis n. sp. sont présentées, ainsi que des perspectives de recherches futures pour mieux comprendre ce genre xiphosuride fossile emblématique

    A molecular palaeobiological exploration of arthropod terrestrialization

    Get PDF
    Understanding animal terrestrialization, the process through which animals colonized the land, is crucial to clarify extant biodiversity and biological adaptation. Arthropoda (insects, spiders, centipedes and their allies) represent the largest majority of terrestrial biodiversity. Here we implemented a molecular palaeobiological approach, merging molecular and fossil evidence, to elucidate the deepest history of the terrestrial arthropods. We focused on the three independent, Palaeozoic arthropod terrestrialization events (those of Myriapoda, Hexapoda and Arachnida) and showed that a marine route to the colonization of land is the most likely scenario. Molecular clock analyses confirmed an origin for the three terrestrial lineages bracketed between the Cambrian and the Silurian. While molecular divergence times for Arachnida are consistent with the fossil record, Myriapoda are inferred to have colonized land earlier, substantially predating trace or body fossil evidence. An estimated origin of myriapods by the Early Cambrian precedes the appearance of embryophytes and perhaps even terrestrial fungi, raising the possibility that terrestrialization had independent origins in crown-group myriapod lineages, consistent with morphological arguments for convergence in tracheal systems. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.© 2016 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited
    corecore