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Evolutionary Fauna (evolutionary + fauna)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

History of marine biodiversity

GEOLOGICAL JOURNAL, Issue 3-4 2001
Peter M. Sheehan
Abstract During the Phanerozoic, three steps of increasing diversity each had a unique Evolutionary Fauna (EF). During each EF, there were geologically long intervals of community stasis referred to as Ecological Evolutionary Units (EEUs). These intervals were characterized by communities composed of incumbent faunas that dominated particular habitats. Niches that were already occupied by incumbents were seldom invaded by new taxa, and the resilience of the incumbents to new competitors resulted in the long interval stasis. Most EEUs were terminated by extinction events that were caused by severe disruptions of the physical environment such as glaciations and extraterrestrial impacts. During mass extinctions many niches were vacated when incumbents were eliminated. Mass extinctions were followed by recovery intervals lasting on the order of 5 million years during which many surviving clades evolved adaptations which allowed them to move into vacated niches. New incumbents were established during these recovery intervals, and the next EEU began. In many ways, the recovery intervals resemble times when organisms invaded previously unoccupied ecospace, such as the emergence of life on land or the progressive filling of previously unoccupied habitats such as deep-burrowing and high epifaunal tiers that were colonized during the Palaeozoic. The recognition of long intervals of ecological stasis and the importance of physical disruptions in clearing incumbents is forcing revision of the traditional evolutionary viewpoint. The idea that most evolutionary change was accomplished very gradually by competition between organisms and by becoming better adapted to a relatively stable environment is being replaced by a recognition that major morphological and synecological changes tend to occur very rapidly and at times when there are few established competitors. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The Ordovician Biodiversification: revolution in the oceanic trophic chain

LETHAIA, Issue 2 2008
THOMAS SERVAIS
The Early Palaeozoic phytoplankton (acritarch) radiation paralleled a long-term increase in sea level between the Early Cambrian and the Late Ordovician. In the Late Cambrian, after the SPICE ,13Ccarb excursion, acritarchs underwent a major change in morphological disparity and their taxonomical diversity increased to reach highest values during the Middle Ordovician (Darriwilian). This highest phytoplankton diversity of the Palaeozoic was possibly the result of palaeogeography (greatest continental dispersal) and major orogenic and volcanic activity, which provided maximum ecospace and large amounts of nutrients. With its warm climate and high atmospheric CO2 levels, the Ordovician was similar to the Cretaceous: a period when phytoplankton diversity was at its maximum during the Mesozoic. With increased phytoplankton availability in the Late Cambrian and Ordovician a radiation of zooplanktonic organisms took place at the same time as a major diversification of suspension feeders. In addition, planktotrophy originated in invertebrate larvae during the Late Cambrian,Early Ordovician. These important changes in the trophic chain can be considered as a major palaeoecological revolution (part of the rise of the Palaeozoic Evolutionary Fauna of Sepkoski). There is now sufficient evidence that this trophic chain revolution was related to the diversification of the phytoplankton, of which the organic-walled fraction is partly preserved. [source]

BILLENGSELLIDE AND ORTHIDE BRACHIOPODS: NEW INSIGHTS INTO EARLIEST ORDOVICIAN EVOLUTION AND BIOGEOGRAPHY FROM NORTHERN IRAN

PALAEONTOLOGY, Issue 1 2009
LEONID E. POPOV
Abstract:, The eastern Alborz Mountains of Iran comprise a significant peri-Gondwanan terrane relevant to the early evolution of late Cambrian , early Ordovician brachiopods incorporated into the emerging benthic biota of the Paleozoic Evolutionary Fauna. A low diversity brachiopod assemblage from the late Tremadocian unit of the Lashkarak Formation contains six new species including the polytoechioideans Polytoechia and Protambonites and the orthoideans Paralenorthis, Ranorthis, Tarfaya and Xianorthis. The fauna preserves the earliest records of Polytoechia, unknown previously outside Laurentia and the Uralian margin of Baltica, and of Paralenorthis and Ranorthis, which were widespread along Gondwanan margins and in Baltica from the Floian (Arenig), plus Xianorthis, known hitherto only from the Floian of South China. The enigmatic Tarfaya has an impunctate shell fabric and setigerous perforations along the posterior margin, indicating placement within the Orthoidea in a new Family Tarfayidae. New species of Polytoechia, Protambonites, Paralenorthis, Ranorthis, Tarfaya, Xianorthis are described. [source]

Temporal Distribution of Diagnostic Biofabrics in the Lower and Middle Ordovician in North China: Clues to the Geobiology of the Great Ordovician Biodiversification Event

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009
Jianbo LIU
Abstract: The temporal distribution of the diagnostic biofabrics in the Lower and Middle Ordovician in North China distinctly illustrates that the sedimentary systems on the paleoplate have been changed markedly as consequences of the Great Ordovician Biodiversification Event (GOBE). The pre-GOBE sedimentary systems deposited in Tremadoc display widespread microbialite and flat-pebble conglomerates, and a less extent of bioturbation. Through the transitional period of early Floian, the sedimentary systems in the rest of the Early and Mid- Ordovician change to GOBE type and are characterized by intensive bioturbation and vanishing flat-pebble conglomerates and subtidal microbial sediments. The irreversible changes in sedimentary systems in North China are linked to the GOBE, which conduced the increase in infaunal tiering, the expansion of infaunal ecospace, and the appearance of new burrowers related to the development of the Paleozoic Evolutionary Fauna during the Ordovician biodiversification. Thus, changes in sedimentary systems during the pivotal period of the GOBE were consequences of a steep diversification of benthic faunas rather than the GOBE's environmental background. [source]