scholarly journals Morphospace saturation in the stem-gnathostomes pteraspidiformes heterostracans: an early radiation of a ‘bottom’ heavy clade

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5249
Author(s):  
Marco Romano ◽  
Robert Sansom ◽  
Emma Randle
Keyword(s):  
Evolutionary History ◽  
Late Devonian ◽  
Gradual Decline ◽  
Early Devonian ◽  
Morphological Disparity ◽  
Anatomical Features ◽  
Early Radiation ◽  
Taxic Diversity ◽  
Shed Light ◽  
Over Time

Ostracoderms (fossil armoured jawless fishes) shed light on early vertebrate evolution by revealing the step-wise acquisition of jawed vertebrate characters, and were important constituents of Middle Palaeozoic vertebrate faunas. A wide variety of head shield shapes are observed within and between the ostracoderm groups, but the timing of these diversifications and the consistency between different measures of their morphospace are unclear. Here, we present the first disparity (explored morphospace) versus diversity (number of taxa) analysis of Pteraspidiformes heterostracans using continuous and discrete characters. Patterns of taxic diversity and morphological disparity are in accordance: they both show a rise to a peak in the Lochkovian followed by a gradual decline in the Middle-Late Devonian. Patterns are largely consistent for disparity measures using sum of ranges or total variance, and when using continuous or discrete characters. Pteraspidiformes heterostracans can be classified as a “bottom-heavy clade”, i.e., a group where a high initial disparity decreasing over time is detected. In fact, the group explored morphospace early in its evolutionary history, with much of the subsequent variation in dermal armour occurring as variation in the proportions of already evolved anatomical features. This Early Devonian radiation is also in agreement with the paleobiogeographic distribution of the group, with a maximum of dispersal and explored morphospace during the Lochkovian and Pragian time bins.

scholarly journals Palynological indications for Silurian – earliest Devonian age strata in the Netherlands

2021 ◽  
Vol 100 ◽  
Author(s):  
Alexander J.P. Houben ◽  
Geert-Jan Vis
Keyword(s):  
The Netherlands ◽  
Core Material ◽  
Late Devonian ◽  
Time Interval ◽  
The South ◽  
Early Devonian ◽  
The North ◽  
Depositional Settings ◽  
Palynological Study ◽  
Devonian Age

Abstract Knowledge of the stratigraphic development of pre-Carboniferous strata in the subsurface of the Netherlands is very limited, leaving the lithostratigraphic nomenclature for this time interval informal. In two wells from the southwestern Netherlands, Silurian strata have repeatedly been reported, suggesting that these are the oldest ever recovered in the Netherlands. The hypothesised presence of Silurian-aged strata has not been tested by biostratigraphic analysis. A similar lack of biostratigraphic control applies to the overlying Devonian succession. We present the results of a palynological study of core material from wells KTG-01 and S05-01. Relatively low-diversity and poorly preserved miospore associations were recorded. These, nonetheless, provide new insights into the regional stratigraphic development of the pre-Carboniferous of the SW Netherlands. The lower two cores from well KTG-01 are of a late Silurian (Ludlow–Pridoli Epoch) to earliest Devonian (Lochkovian) age, confirming that these are the oldest sedimentary strata ever recovered in the Netherlands. The results from the upper cored section from the pre-Carboniferous succession in well KTG-01 and the cored sections from the pre-Carboniferous succession in well S05-01 are more ambiguous. This inferred Devonian succession is, in the current informal lithostratigraphy of the Netherlands, assigned to the Banjaard group and its subordinate Bollen Claystone formation, of presumed Frasnian (i.e. early Late Devonian) age. Age-indicative Middle to Late Devonian palynomorphs were, however, not recorded, and the overall character of the poorly preserved palynological associations in wells KTG-01 and S05-01 may also suggest an Early Devonian age. In terms of lithofacies, however, the cores in well S05-01 can be correlated to the upper Frasnian – lower Famennian Falisolle Formation in the Campine Basin in Belgium. Hence, it remains plausible that an unconformity separates Silurian to Lower Devonian strata from Upper Devonian (Frasnian–Famennian) strata in the SW Netherlands. In general, the abundance of miospore associations points to the presence of a vegetated hinterland and a relatively proximal yet relatively deep marine setting during late Silurian and Early Devonian times. This differs markedly from the open marine depositional settings reported from the Brabant Massif area to the south in present-day Belgium, suggesting a sediment source to the north. The episodic presence of reworked (marine) acritarchs of Ordovician age suggests the influx of sedimentary material from uplifted elements on the present-day Brabant Massif to the south, possibly in relation to the activation of a Brabant Arch system.

scholarly journals Evolutionary history of zoogeographical regions surrounding the Tibetan Plateau

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jiekun He ◽  
Siliang Lin ◽  
Jiatang Li ◽  
Jiehua Yu ◽  
Haisheng Jiang
Keyword(s):  
Tibetan Plateau ◽  
Evolutionary History ◽  
The Tibetan Plateau ◽  
Change Over Time ◽  
Deep Time ◽  
Terrestrial Vertebrates ◽  
History Of ◽  
Striking Change ◽  
Time Periods ◽  
Over Time

AbstractThe Tibetan Plateau (TP) and surrounding regions have one of the most complex biotas on Earth. However, the evolutionary history of these regions in deep time is poorly understood. Here, we quantify the temporal changes in beta dissimilarities among zoogeographical regions during the Cenozoic using 4,966 extant terrestrial vertebrates and 1,278 extinct mammal genera. We identify ten present-day zoogeographical regions and find that they underwent a striking change over time. Specifically, the fauna on the TP was close to the Oriental realm in deep time but became more similar to the Palearctic realms more recently. The present-day zoogeographical regions generally emerged during the Miocene/Pliocene boundary (ca. 5 Ma). These results indicate that geological events such as the Indo-Asian Collision, the TP uplift, and the aridification of the Asian interior underpinned the evolutionary history of the zoogeographical regions surrounding the TP over different time periods.

scholarly journals Nephromyces represents a diverse and novel lineage of the Apicomplexa that has retained apicoplasts

2019 ◽  
Author(s):  
Sergio A Muñoz-Gómez ◽  
Keira Durnin ◽  
Laura Eme ◽  
Christopher Paight ◽  
Christopher E Lane ◽  
...  
Keyword(s):  
Life Style ◽  
Metabolic Pathways ◽  
Evolutionary History ◽  
Phylogenetic Analyses ◽  
Phylogenetic Position ◽  
Biosynthetic Pathways ◽  
History Of ◽  
Sea Squirts ◽  
Shed Light ◽  
Apicoplast Genome

Abstract A most interesting exception within the parasitic Apicomplexa is Nephromyces, an extracellular, probably mutualistic, endosymbiont found living inside molgulid ascidian tunicates (i.e., sea squirts). Even though Nephromyces is now known to be an apicomplexan, many other questions about its nature remain unanswered. To gain further insights into the biology and evolutionary history of this unusual apicomplexan, we aimed to (1) find the precise phylogenetic position of Nephromyces within the Apicomplexa, (2) search for the apicoplast genome of Nephromyces, and (3) infer the major metabolic pathways in the apicoplast of Nephromyces. To do this, we sequenced a metagenome and a metatranscriptome from the molgulid renal sac, the specialized habitat where Nephromyces thrives. Our phylogenetic analyses of conserved nucleus-encoded genes robustly suggest that Nephromyces is a novel lineage sister to the Hematozoa, which comprises both the Haemosporidia (e.g., Plasmodium) and the Piroplasmida (e.g., Babesia and Theileria). Furthermore, a survey of the renal sac metagenome revealed 13 small contigs that closely resemble the genomes of the non-photosynthetic reduced plastids, or apicoplasts, of other apicomplexans. We show that these apicoplast genomes correspond to a diverse set of most closely related but genetically divergent Nephromyces lineages that co-inhabit a single tunicate host. In addition, the apicoplast of Nephromyces appears to have retained all biosynthetic pathways inferred to have been ancestral to parasitic apicomplexans. Our results shed light on the evolutionary history of the only probably mutualistic apicomplexan known, Nephromyces, and provide context for a better understanding of its life style and intricate symbiosis.

A Quantitative Study of the Paratexts in Erasmus-Froben Imprints

2021 ◽  
Vol 41 (2) ◽  
pp. 99-181
Author(s):  
Ann Blair ◽  
Maryam Patton
Keyword(s):  
Quantitative Study ◽  
16Th Century ◽  
Shed Light ◽  
Over Time

Abstract We study the paratexts in Erasmus’ imprints with Johann then Hieronymus Froben of Basel between 1514 and 1536. From Valentina Sebastiani’s bibliography of Johann Froben we observe that Erasmus was a more abundant paratexter than other authors who published with Johann Froben. We supplement that work with a bibliography of Erasmus’ imprints with Hieronymus Froben. We note trends across the Erasmus-Froben corpus, including: a remarkable number of imprints, equally balanced between new editions and re-editions, abundant dedications without correlation to format, indexes in folio volumes especially, a growing attention to errata lists over time. These patterns shed light on one author-printer partnership but also on more general trends in learned publishing in the early 16th century.

scholarly journals The origin and early radiation of terrestrial vertebrates

2001 ◽  
Vol 75 (6) ◽  
pp. 1202-1213 ◽  
Author(s):  
Robert L. Carroll
Keyword(s):  
Fossil Record ◽  
Early Carboniferous ◽  
Late Devonian ◽  
Lower Carboniferous ◽  
Major Transitions ◽  
Terrestrial Vertebrates ◽  
History Of ◽  
Paleozoic Tetrapods ◽  
Early Radiation ◽  
Ways Of Life

The origin of tetrapods from sarcopterygian fish in the Late Devonian is one of the best known major transitions in the history of vertebrates. Unfortunately, extensive gaps in the fossil record of the Lower Carboniferous and Triassic make it very difficult to establish the nature of relationships among Paleozoic tetrapods, or their specific affinities with modern amphibians. The major lineages of Paleozoic labyrinthodonts and lepospondyls are not adequately known until after a 20–30 m.y. gap in the Early Carboniferous fossil record, by which time they were highly divergent in anatomy, ways of life, and patterns of development. An even wider temporal and morphological gap separates modern amphibians from any plausible Permo-Carboniferous ancestors. The oldest known caecilian shows numerous synapomorphies with the lepospondyl microsaur Rhynchonkos. Adult anatomy and patterns of development in frogs and salamanders support their origin from different families of dissorophoid labyrinthodonts. The ancestry of amniotes apparently lies among very early anthracosaurs.

scholarly journals MAKING A CHANGE FROM BELOW

Traditiones ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 75-91
Author(s):  
Daša Ličen ◽  
Dan Podjed
Keyword(s):  
Public Space ◽  
Critical Mass ◽  
Waste Reduction ◽  
Social Transition ◽  
Environmental Movements ◽  
The Social ◽  
Grassroots Initiatives ◽  
Ethnographic Analysis ◽  
Shed Light ◽  
Over Time

The authors look into two environmental movements that arose from grassroots initiatives. The first is Ecologists without Borders, the leading NGO promoting waste reduction in Slovenia. The second is Critical Mass, an international cyclists’ movement that seeks more public space for urban cyclists, which the authors studied in Belgrade and Budapest. Ethnographic analysis indicates that the two movements have had certain common experiences. The authors use these cases to investigate the social transition that such movements support and shed light on how they arise, function, and change over time.

Wood anatomy of the Mascarene Dombeyoideae: Systematic and ecological implications

IAWA Journal ◽  
2011 ◽  
Vol 32 (4) ◽  
pp. 493-519 ◽  
Author(s):  
Anaïs Boura ◽  
Timothée Le Péchon ◽  
Romain Thomas
Keyword(s):  
Evolutionary History ◽  
Wood Anatomy ◽  
Sister Group ◽  
Biological Data ◽  
Sister Group Relationship ◽  
Anatomical Features ◽  
Ecological Implications ◽  
History Of ◽  
Mascarene Islands ◽  
Almost All

The Dombeyoideae (Malvaceae) are one of the most diversified groups of plants in the Mascarene Islands. Species of Dombeya Cav., Ruizia Cav. and Trochetia DC. are distributed in almost all parts of the archipelago and show a wide diversity in their growth forms. This study provides the first wood anatomical descriptions of 17 out of the 22 Mascarene species of Dombeyoideae. Their wood anatomy is similar to that of previously described species: wide vessels, presence of both apotracheal and paratracheal parenchyma, and storied structure. In addition, we also found a second wood anatomical pattern with narrower vessels, high vessel frequency and thick-walled fibres. The two aforementioned wood patterns are considered in a phylogenetic context and used to trace the evolutionary history of several wood anatomical features. For example, the pseudoscalariform pit arrangement supports a sister group relationship between Trochetia granulata Cordem. and T. blackburniana Bojer ex Baker and may be a new synapomorphy of the genus Trochetia. Finally, wood variability is evaluated in relation to geographic, climatic and biological data. Despite the juvenile nature of some of the specimens studied, we discuss how the habit, but also factors related to humidity, influence the variability observed in the Mascarene Dombeyoideae wood structure.

The coming age of adversarial social bot detection

First Monday ◽  
2021 ◽  
Author(s):  
Stefano Cresci ◽  
Marinella Petrocchi ◽  
Angelo Spognardi ◽  
Stefano Tognazzi
Keyword(s):  
Machine Learning ◽  
Computer Security ◽  
Field Of Study ◽  
True Nature ◽  
Proactive Approach ◽  
Bot Detection ◽  
Illegal Activities ◽  
Shed Light ◽  
Over Time

Social bots are automated accounts often involved in unethical or illegal activities. Academia has shown how these accounts evolve over time, becoming increasingly smart at hiding their true nature by disguising themselves as genuine accounts. If they evade, bots hunters adapt their solutions to find them: the cat and mouse game. Inspired by adversarial machine learning and computer security, we propose an adversarial and proactive approach to social bot detection, and we call scholars to arms, to shed light on this open and intriguing field of study.

Premature Predicaments

2019 ◽  
pp. 29-58
Author(s):  
Dána-Ain Davis
Keyword(s):  
Nineteenth Century ◽  
Birth Outcomes ◽  
Premature Birth ◽  
Harriet Jacobs ◽  
Birth Stories ◽  
Racial Science ◽  
Shed Light ◽  
Over Time ◽  
Autobiographical Narrative

This chapter examines the definitions of prematurity over time and specifically explores how racial science has been used to animate the definitions and etiology, or causes, of premature birth. This chapter focuses on the birth stories of four women, who gave birth prematurely in different centuries, between the nineteenth century and the present, to shed light on the temporality of Black women’s birth outcomes. The birth stories, including one contained in Incidents in the Life of a Slave Girl, an autobiographical narrative by Harriet Jacobs, highlight questions about the definition and etiology of prematurity. The stories also illustrate some of the clinical causes of premature birth and present the situations that women describe as evidence of medical racism.

The grieving killjoy: Bereavement, alienation and cultural critique

2020 ◽  
pp. 1354067X2092213
Author(s):  
Ester H Kofod
Keyword(s):  
Cultural Critique ◽  
Emotional Pain ◽  
Gradual Decline ◽  
The Past ◽  
Cultural Ideals ◽  
Bereaved Parents ◽  
Starting Point ◽  
Normative Standards ◽  
Bereavement Research ◽  
Shed Light

In recent years, a range of scholars have put forth critical analyses of the consequences of the ideals of happiness, future-orientedness, and productivity which dominate contemporary Western cultures. The experience of grief—with its sadness, preoccupation with the past, and lack of initiative—is inherently at odds with such ideals. This conflict between grief and cultural ideals of happiness is reflected in the recent efforts within bereavement research to delineate pathological mourning from uncomplicated, normative mourning. While the latter is characterized by a gradual decline in emotional pain, sadness, lack of initiative, etc., complicated mourning is marked by a failure to meet normative standards for recovery. In this article, I will draw on loss experiences among bereaved parents in contemporary Danish society in order to shed light on how profound losses may catalyze estrangement from and opposition toward what has been termed the happiness imperative of contemporary Western societies. More specifically, I borrow the figure of the feminist killjoy, paraphrased as the grieving killjoy, as a lens through which bereavement experiences may be theorized and understood as a starting point for experientially driven cultural critique.

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