The early Mesozoic radiation of dinoflagellates

Paleobiology ◽  
1996 ◽  
Vol 22 (3) ◽  
pp. 329-338 ◽  
Author(s):  
R. A. Fensome ◽  
R. A. MacRae ◽  
J. M. Moldowan ◽  
F. J. R. Taylor ◽  
G. L. Williams
Keyword(s):  
Detailed Analysis ◽  
Fossil Record ◽  
The Past ◽  
Early Mesozoic ◽  
Fossil Evidence ◽  
Evolutionary Radiation ◽  
Molecular Phylogenetic ◽  
Sudden Appearance ◽  
New Evidence

Dinoflagellates are a major component of the marine microplankton and, from fossil evidence, appear to have been so for the past 200 million years. In contrast, the pre-Triassic record contains only equivocal occurrences of dinoflagellates, despite the fact that comparative ultrastructural and molecular phylogenetic evidence indicates a Precambrian origin for the lineage. Thus, it has often been assumed that the dearth of Paleozoic fossil dinoflagellates was due to a lack of preservation or recognition and that the relatively sudden appearance of dinoflagellates in the Mesozoic is an artifact of the record. However, new evidence from a detailed analysis of the fossil record and from the biogeochemical record indicates that dinoflagellates did indeed undergo a major evolutionary radiation in the early Mesozoic.

scholarly journals How the past impacts the future: modelling the performance of evolutionarily distinct mammals through time

2019 ◽  
Vol 374 (1788) ◽  
pp. 20190210 ◽  
Author(s):  
D. J. Bennett ◽  
M. D. Sutton ◽  
S. T. Turvey
Keyword(s):  
Fossil Record ◽  
Distinct Species ◽  
Performance Impact ◽  
Deep Time ◽  
The Past ◽  
Living Fossils ◽  
Measuring Change ◽  
Molecular Phylogenetic ◽  
Time Changes ◽  
The One

How does past evolutionary performance impact future evolutionary performance? This is an important question not just for macroevolutionary biologists who wish to chart the phenomena that describe deep-time changes in biodiversity but also for conservation biologists, as evolutionarily distinct species—which may be deemed ‘low-performing’ in our current era—are increasingly the focus of conservation efforts. Contrasting hypotheses exist to account for the history and future of evolutionarily distinct species: on the one hand, they may be relicts of large radiations, potentially ‘doomed’ to extinction; or they may be slow-evolving, ‘living fossils’, likely neither to speciate nor go extinct; or they may be seeds of future radiations. Here, we attempt to test these hypotheses in Mammalia by combining a molecular phylogenetic supertree with fossil record occurrences and measuring change in evolutionary distinctness (ED) at different time slices. With these time slices, we modelled future ED as a function of past ED. We find that past evolutionary performance does indeed have an impact on future evolutionary performance: the most evolutionarily isolated clades tend to become more evolutionarily distinct with time, indicating that low-performing clades tend to remain low-performing throughout their evolutionary history. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

Introduction to the Symposium on Tempo and Mode of Evolution from Micropaleontological Data

Paleobiology ◽  
1983 ◽  
Vol 9 (4) ◽  
pp. 326-326 ◽  
Author(s):  
William A. Berggren ◽  
Richard E. Casey
Keyword(s):  
New Species ◽  
Morphological Change ◽  
Fossil Record ◽  
Punctuated Equilibria ◽  
Principal Mode ◽  
The Past ◽  
Species Formation ◽  
Sudden Appearance ◽  
A New Species ◽  
Occurrence Of Species

The concept of punctuated equilibria was introduced by Eldredge and Gould (1972) as an interpretation of the sequential occurrence of species as actually observed in the fossil record. The pattern of sudden appearance of a new species followed by little or no morphological change during the remainder of the species' existence contrasts with phyletic gradualism, the pattern of slower, more evenly distributed change which was long considered to be the principal mode of species formation (Simpson 1944). The question of which is the dominant pattern of evolutionary change has continued as an actively debated theme in much of the paleontological literature of the past decade.

Are modern chemosynthesis-based communities a ‘glimpse of antiquity’? The changing fate of bivalves and brachiopods at ancient methane seeps as recorded in the Middle Palaeozoic of Morocco

2020 ◽  
Author(s):  
Michał Jakubowicz ◽  
Krzysztof Hryniewicz
Keyword(s):  
Middle Devonian ◽  
Fossil Record ◽  
Hydrothermal Vents ◽  
Upper Devonian ◽  
Early Evolution ◽  
Methane Seeps ◽  
The Past ◽  
Early Mesozoic ◽  
Morphological Adaptations ◽  
Chemosynthetic Ecosystems

<p>Despite much scientific effort aimed over the past three decades to better constrain the fossil record of chemosynthesis-based communities, our understanding of their early evolution remains fragmentary. Until recently, a dominant perception was that, unlike the Cenozoic, bivalve-dominated chemosynthetic ecosystems, the Paleozoic to mid-Mesozoic methane seeps and hydrothermal vents were dominated by brachiopods. Similarly, the pattern of brachiopod vs. bivalve predominance at seeps and vents over the Phanerozoic was believed to have crudely followed that observed in normal-marine benthic shelly assemblages. Recent discoveries from the Middle Palaeozoic of Morocco have questioned this simple perception, documenting the presence of late Silurian and Middle Devonian seeps dominated by mass accumulations of large, semi-infaunal, modiomorphid bivalves (Hryniewicz et al., 2017; Jakubowicz et al., 2017). While representing a lineage unrelated to modern seep-obligate bivalve taxa, the mid-Palaeozoic seep bivalves developed a set of morphological adaptations strikingly similar to those of their modern ecological counterparts, and formed analogous, densely-packed, nearly monospecific assemblages, both suggesting their chemosymbiotic lifestyle. The new documentation of Palaeozoic establishment of the bivalve-dominated seep communities provides a fresh look at the concept of modern chemosynthetic ecosystems as a 'glimpse of antiquity', showing that although it is largely not true taxonomically, it clearly is in terms of recurring morphological themes. At the same time, this refined Palaeozoic record makes the factors responsible for the apparent scarcity of seep-related bivalves during the upper Devonian to early Mesozoic, a period of the remarkable success of brachiopod-dominated seep assemblages, ever more enigmatic.</p>

9. The future of human evolution

2019 ◽  
pp. 120-126
Author(s):  
Bernard Wood
Keyword(s):  
Molecular Biology ◽  
Human Evolution ◽  
New Taxa ◽  
Fossil Record ◽  
Imaging Techniques ◽  
Modern Humans ◽  
Fossil Evidence ◽  
The Future ◽  
New Locations ◽  
New Evidence

What are the next few decades likely to bring in terms of new evidence about human evolution? Are modern humans still evolving, and if so, what changes are we likely to see? ‘The future of human evolution’ considers both of these questions. It explains that researchers will continue to look for additional fossil evidence, at existing fossil sites as well as in new locations. Both will provide valuable evidence. It considers the chances of finding new taxa and how more evidence can be squeezed out of the existing fossil record through improved molecular biology and imaging techniques. Finally, it looks at contemporary human evolution and what is likely to influence the future of our species.

Evidence of pteridophyte–arthropod interactions in the fossil record

1985 ◽  
Vol 86 ◽  
pp. 133-140 ◽  
Author(s):  
A. C. Scott ◽  
W. G. Chaloner ◽  
S. Paterson
Keyword(s):  
Plant Tissue ◽  
Fossil Record ◽  
Flowering Plants ◽  
Gut Contents ◽  
Insect Pollination ◽  
The Past ◽  
Fossil Evidence ◽  
Source Plant ◽  
History Of ◽  
Xylem Elements

SynopsisThe past decade has seen the emergence of significant fossil evidence of a history of pterodophytearthropod interaction extending back to the Devonian period. Such fossils include plant tissue showing lesions, bites and borings with associated features implicating arthropods as causal agents. Gut contents of Carboniferous arthropods, which include lycopod xylem elements and spores, are a tangible demonstration of phytophagy. Pteridophyte spores in fossil droppings (coprolites) indicate the prevalence of arthropod spore-eating in the Palaeozoic. This may have had compensations for the source plant and evidently represented the start of the co–evolution which culminated in the elaborate adaptations shown by flowering plants and their insect pollination vectors.

scholarly journals Emergency management of the paediatric patient with convulsive status epilepticus

2021 ◽  
Vol 26 (1) ◽  
pp. 50-57
Author(s):  
Kyle C McKenzie ◽  
Cecil D Hahn ◽  
Jeremy N Friedman
Keyword(s):  
Clinical Practice ◽  
Status Epilepticus ◽  
Emergency Management ◽  
Treatment Algorithm ◽  
Position Statement ◽  
Convulsive Status Epilepticus ◽  
Pharmacological Management ◽  
The Past ◽  
New Treatment ◽  
New Evidence

Abstract This guideline addresses the emergency management of convulsive status epilepticus (CSE) in children and infants older than 1 month of age. It replaces a previous position statement from 2011, and includes a new treatment algorithm and table of recommended medications based on new evidence and reflecting the evolution of clinical practice over the past several years. This statement emphasizes the importance of timely pharmacological management of CSE, and includes some guidance for diagnostic approach and supportive care.

Mathematical Issues Arising From the Directed Mutation Controversy

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 373-379
Author(s):  
Qi Zheng
Keyword(s):  
Mathematical Reasoning ◽  
Large Body ◽  
Directed Mutation ◽  
The Past ◽  
New Evidence

Abstract During the past 14 years or so a large body of new evidence that supposedly supports the directed mutation hypothesis has accumulated. Interpretation of some of the evidence depends on mathematical reasoning, which can be subtler than it appears at first sight. This article attempts to clarify some of the mathematical issues arising from the directed mutation controversy, thereby offering alternative interpretations of some of the evidence.

Did Ground Cover Change Over Geologic Time?

2000 ◽  
Vol 6 ◽  
pp. 171-182 ◽  
Author(s):  
Ben A. LePage ◽  
Hermann W. Pfefferkorn
Keyword(s):  
Fossil Record ◽  
Ground Cover ◽  
The Other ◽  
Detailed Account ◽  
Geologic Time ◽  
The Past ◽  
Other Hand ◽  
Plant Fossil

When one hears the term “ground cover,” one immediately thinks of “grasses.” This perception is so deep-seated that paleobotanists even have been overheard to proclaim that “there was no ground cover before grasses.” Today grasses are so predominant in many environments that this perception is perpetuated easily. On the other hand, it is difficult to imagine the absence or lack of ground cover prior to the mid-Tertiary. We tested the hypothesis that different forms of ground cover existed in the past against examples from the Recent and the fossil record (Table 1). The Recent data were obtained from a large number of sources including those in the ecological, horticultural, and microbiological literature. Other data were derived from our knowledge of Precambrian life, sedimentology and paleosols, and the plant fossil record, especially in situ floras and fossil “monocultures.” Some of the data are original observations, but many others are from the literature. A detailed account of these results will be presented elsewhere (Pfefferkorn and LePage, in preparation).

scholarly journals The fossil record of whip spiders: the past of Amblypygi

PalZ ◽  
2021 ◽  
Author(s):  
Carolin Haug ◽  
Joachim T. Haug
Keyword(s):  
Fossil Record ◽  
3D Imaging ◽  
Three Dimensional ◽  
Dorsal Shield ◽  
Stereo Images ◽  
Geological Time ◽  
High Quality ◽  
The Past ◽  
Over Time

AbstractWhip spiders (Amblypygi), as their name suggests, resemble spiders (Araneae) in some aspects, but differ from them by their heart-shaped (prosomal) dorsal shield, their prominent grasping pedipalps, and their subsequent elongate pair of feeler appendages. The oldest possible occurrences of whip spiders, represented by cuticle fragments, date back to the Devonian (c. 385 mya), but (almost) complete fossils are known from the Carboniferous (c. 300 mya) onwards. The fossils include specimens preserved on slabs or in nodules (Carboniferous, Cretaceous) as well as specimens preserved in amber (Cretaceous, Eocene, Miocene). We review here all fossil whip spider specimens, figure most of them as interpretative drawings or with high-quality photographs including 3D imaging (stereo images) to make the three-dimensional relief of the specimens visible. Furthermore, we amend the list by two new specimens (resulting in 37 in total). The fossil specimens as well as modern whip spiders were measured to analyse possible changes in morphology over time. In general, the shield appears to have become relatively broader and the pedipalps and walking appendages have become more elongate over geological time. The morphological details are discussed in an evolutionary framework and in comparison with results from earlier studies.

Factors that Impede or Facilitate Post-Conflict Justice Mechanisms?

2012 ◽  
Vol 12 (2) ◽  
pp. 193-217 ◽  
Author(s):  
Dawn L. Rothe ◽  
Scott Maggard
Keyword(s):  
Detailed Analysis ◽  
The State ◽  
Policy Implications ◽  
Empirical Testing ◽  
Power Politics ◽  
The Past ◽  
Post Conflict

This article provides an overview of post-conflict justice (PCJ) as well as a detailed analysis of factors that impede or facilitate the implementation of mechanisms to address the atrocities of a conflict. Grounded in an extensive new dataset, developed over the past three years, covering all conflicts in Africa between 1946 and 2009, we extend previous research by including empirical testing of previously untested assumptions and variables impacting PCJ, most notably, the role of power, politics, economics, and geo-strategic interests at the state and international political levels as well as combining previously tested variables amongst and between each other. Further, the aspects of PCJ, including conflicts where mechanisms were not deployed are included in the analysis along with those coded as symbolic in nature. We conclude by discussing the pragmatic issues associated with testing the concept of realpolitik and policy implications based on our analysis.

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