scholarly journals Ontogeny of highly variable ceratitid ammonoids from the Anisian (Middle Triassic)

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10931
Author(s):  
Eva Alexandra Bischof ◽  
Nils Schlüter ◽  
Dieter Korn ◽  
Jens Lehmann
Keyword(s):  
Cross Sections ◽  
Middle Triassic ◽  
Phenotypic Variability ◽  
Taxonomic Diversity ◽  
Ontogenetic Changes ◽  
Knowledge Based ◽  
Ontogenetic Trajectories ◽  
Early Middle Triassic ◽  
First Time ◽  
High Diversity

Ammonoids reached their greatest diversity during the Triassic period. In the early Middle Triassic (Anisian) stage, ammonoid diversity was dominated by representatives of the family Ceratitidae. High taxonomic diversity can, however, be decoupled from their morphologic disparity. Due to its high phenotypic variability, the high diversity of ceratitids of the Anisian of Nevada was initially assumed to be caused by artificial over-splitting. This study aims to contribute data to settle this issue by applying geometric morphometrics methods, using landmarks and semi-landmarks, in the study of ontogenetic cross-sections of ammonoids for the first time. The results reveal that alterations in ontogenetic trajectories, linked to heterochronic processes, lead to the morphologic diversification of the species studied herein. Our knowledge, based on these ontogenetic changes, challenge the traditional treatment of species using solely adult characters for their distinction. This study furthermore demonstrates that the high diversity of the Anisian ammonoid assemblages of Nevada based on the traditional nomenclatoric approach is regarded to be reasonably accurate.

scholarly journals Ontogenetic analysis of Anisian (Middle Triassic) ptychitid ammonoids from Nevada, USA

2020 ◽  
Vol 94 (5) ◽  
pp. 829-851
Author(s):  
Eva A. Bischof ◽  
Jens Lehmann
Keyword(s):  
New Species ◽  
Cross Sections ◽  
Middle Triassic ◽  
Taxonomic Diversity ◽  
Species Level ◽  
Species Ranges ◽  
Novel Approach ◽  
Ontogenetic Trajectories ◽  
Diversity Studies ◽  
First Time

AbstractPtychites is among the most widely distributed ammonoid genera of the Triassic and is namesake of a family and superfamily. However, representatives of the genus mostly show low-level phenotypic disparity. Furthermore, a large number of taxa are based on only a few poorly preserved specimens, creating challenges to determine ptychitid taxonomy. Consequently, a novel approach is needed to improve ptychitid diversity studies. Here, we investigate Ptychites spp. from the middle and late Anisian of Nevada. The species recorded include Ptychites embreei n. sp., which is distinguished by an average conch diameter that is much smaller and shows a more evolute coiling than most of its relatives. The new species ranges from the Gymnotoceras mimetus to the Gymnotoceras rotelliformis zones, which makes it the longest-ranging species of the genus. For the first time, the ontogenetic development of Ptychites was obtained from cross sections where possible. Cross-sectioning highlights unique ontogenetic trajectories in ptychitids. This demonstrates that, despite showing little phenotypic disparity, Ptychites was highly ontogenetically differentiated, and thus the high taxonomic diversity at the species level is justified for the species investigated.UUID: http://zoobank.org/5abe2487-8a00-4b48-adc7-ec7db7a097f7

scholarly journals Early evolution of beetles regulated by the end-Permian deforestation

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Xianye Zhao ◽  
Yilun Yu ◽  
Matthew E Clapham ◽  
Evgeny Yan ◽  
Jun Chen ◽  
...  
Keyword(s):  
Forest Ecosystems ◽  
Middle Triassic ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
Taxonomic Diversity ◽  
Data Set ◽  
Deep Time ◽  
Ecological Shifts ◽  
Permian Mass Extinction ◽  
Early Middle Triassic

The end-Permian mass extinction (EPME) led to a severe terrestrial ecosystem collapse. However, the ecological response of insects—the most diverse group of organisms on Earth—to the EPME remains poorly understood. Here, we analyse beetle evolutionary history based on taxonomic diversity, morphological disparity, phylogeny, and ecological shifts from the Early Permian to Middle Triassic, using a comprehensive new data set. Permian beetles were dominated by xylophagous stem groups with high diversity and disparity, which probably played an underappreciated role in the Permian carbon cycle. Our suite of analyses shows that Permian xylophagous beetles suffered a severe extinction during the EPME largely due to the collapse of forest ecosystems, resulting in an Early Triassic gap of xylophagous beetles. New xylophagous beetles appeared widely in the early Middle Triassic, which is consistent with the restoration of forest ecosystems. Our results highlight the ecological significance of insects in deep-time terrestrial ecosystems.

scholarly journals The radiation of cynodonts and the ground plan of mammalian morphological diversity

2013 ◽  
Vol 280 (1769) ◽  
pp. 20131865 ◽  
Author(s):  
Marcello Ruta ◽  
Jennifer Botha-Brink ◽  
Stephen A. Mitchell ◽  
Michael J. Benton
Keyword(s):  
Middle Triassic ◽  
Morphological Diversity ◽  
Late Permian ◽  
Heterogeneous Distribution ◽  
Ground Plan ◽  
Extinction Event ◽  
The Mean ◽  
Mass Extinction Event ◽  
Early Middle Triassic ◽  
High Diversity

Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic. We use an enlarged and revised dataset of discrete skeletal characters to build a new phylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are non-significant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades.

scholarly journals Early evolution of beetles regulated by the end-Permian deforestation

2021 ◽  
Author(s):  
Xianye Zhao ◽  
Yilun Yu ◽  
Matthew Clapham ◽  
Evgeny Yan ◽  
Jun Chen ◽  
...  
Keyword(s):  
Forest Ecosystems ◽  
Middle Triassic ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
Taxonomic Diversity ◽  
Data Set ◽  
Deep Time ◽  
Ecological Shifts ◽  
Permian Mass Extinction ◽  
Early Middle Triassic

The end-Permian mass extinction (EPME) led to a severe terrestrial ecosystem collapse. However, the ecological response of insects—the most diverse group of organisms on Earth—to the EPME remains poorly understood. Here, we analyse beetle evolutionary history based on taxonomic diversity, morphological disparity, phylogeny, and ecological shifts from the Early Permian to Middle Triassic, using a comprehensive new data set. Permian beetles were dominated by xylophagous stem groups with a high diversity and disparity, which probably played an underappreciated role in the Permian carbon cycle. Our suite of analyses shows that Permian xylophagous beetles suffered a severe extinction during the EPME largely due to the collapse of forest ecosystems, resulting in an Early Triassic gap of xylophagous beetles. New xylophagous beetles appeared widely in the early Middle Triassic, which is consistent with the restoration of forest ecosystems. Our results highlight the ecological significance of insects in deep-time terrestrial ecosystems.

The Mechanics of the Secondary Flows of Viscoelastic Fluids in Non-Circular Straight Tubes and the Mean Transversal Field in Pulsating Flows

2000 ◽  
Author(s):  
Dennis A. Siginer ◽  
Mario F. Letelier
Keyword(s):  
Secondary Flow ◽  
Cross Sections ◽  
Viscoelastic Fluids ◽  
Secondary Flows ◽  
Novel Approach ◽  
Transversal Field ◽  
Time Domains ◽  
Viscoelastic Liquids ◽  
First Time ◽  
Secondary Flow Field

Abstract A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid, whose structure is defined by a series of nested integrals over semi-infinite time domains, in straight tubes of arbitrary cross-sections is summarized. The transversal field arises at the second order of the perturbation of the nonlinear constitutive structure, and is driven by first order terms which define the linearly viscoelastic longitudinal flow in the hierarchy of superposed linear flows stemming from the perturbation of the constitutive structure. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

Paleobiology ◽  
2021 ◽  
pp. 1-23
Author(s):  
Pablo S. Milla Carmona ◽  
Dario G. Lazo ◽  
Ignacio M. Soto
Keyword(s):  
Trajectory Analysis ◽  
Sedentary Lifestyle ◽  
Shape Change ◽  
Shell Shape ◽  
Shape Variation ◽  
Ontogenetic Changes ◽  
Ontogenetic Trajectories ◽  
Higher Genus ◽  
Gradual Decay

Abstract Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

scholarly journals Performance Evaluation of a Nanomaterial-Based Thermoelectric Generator with Tapered Legs

2020 ◽  
Vol 7 ◽  
pp. 48-54
Author(s):  
Marilyn A. Ebiringa ◽  
John Paul Adimonyemma ◽  
Chika Maduabuchi
Keyword(s):  
Cross Sections ◽  
Thermoelectric Generator ◽  
Bulk Material ◽  
Electrical Energy ◽  
Ansys Software ◽  
Thermoelectric Effects ◽  
Trapezoidal Shape ◽  
Solar Radiation Intensity ◽  
Geometry Configuration ◽  
First Time

A thermoelectric generator (TEG) converts thermal energy to electricity using thermoelectric effects. The amount of electrical energy produced is dependent on the thermoelectric material properties. Researchers have applied nanomaterials to TEG systems to further improve the device’s efficiency. Furthermore, the geometry of the thermoelectric legs has been varied from rectangular to trapezoidal and even X-cross sections to improve TEG’s performance further. However, up to date, a nanomaterial TEG that uses tapered thermoelectric legs has not been developed before. The most efficient nanomaterial TEGs still make use of the conventional rectangular leg geometry. Hence, for the first time since the conception of nanostructured thermoelectrics, we introduce a trapezoidal shape configuration in the device design. The leg geometries were simulated using ANSYS software and the results were post-processed in the MATLAB environment. The results show that the power density of the nanoparticle X-leg TEG was 10 times greater than that of the traditional bulk material semiconductor X-leg TEG. In addition, the optimum leg geometry configuration in a nanomaterial-based TEG is dependent on the operating solar radiation intensity.

scholarly journals CROSS-SECTIONS FOR PHOTONUCLEAR REACTIONS 93Nb(γ,n)92mNb AND 93Nb(γ,n)92tNb IN THE END-POINT BREMSSTRAHLUNG ENERGIES 36...91 MeV

2020 ◽  
pp. 148-153
Author(s):  
A.N. Vodin ◽  
O.S. Deiev ◽  
I.S. Timchenko ◽  
S.N. Olejnik ◽  
A.S. Kachan ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Bremsstrahlung Spectrum ◽  
Photonuclear Reactions ◽  
End Point ◽  
Γ Ray ◽  
First Time ◽  
Good Agreement

The flux-weighted averaged over the energy range of bremsstrahlung spectrum from reaction threshold up to the maximum energy of γ-ray cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb photonuclear reactions were determined by the gamma-activation method within the end-point bremsstrahlung energies Еmax = 36…91 MeV. Activation of 93Nb targets has been done by a bremsstrahlung flux using an electron beam at the linear accelerator LUE-40 at RDC "Accelerator" NSC KIPT. The γ-ray spectra of irradiated targets were registered using the HPGe detector with an energy resolution of 1.8 keV for the 1332 keV line 60Co. To control the bremsstrahlung flux we used natMo witness-targets and a reaction cross-section of 100Mo(γ,n)99Mo. Obtained experimental cross-sections <σ(E)> of the studied reactions are in good agreement with the theoretical values calculated within TALYS 1.9 code and the results of other authors. The averaged cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb reactions in the energy range 35...45 MeV and > 70 MeV were obtained for the first time.

scholarly journals Aeromedical evacuation of a COVID-19 patient from a zonal hospital: A case report

2021 ◽  
Vol 65 ◽  
pp. 51-54
Author(s):  
S Patnaik ◽  
LK Dash ◽  
G Rajaram ◽  
C Chattophadhayay
Keyword(s):  
Armed Forces ◽  
Aeromedical Evacuation ◽  
Knowledge Based ◽  
Global Pandemic ◽  
Life Saving ◽  
Tertiary Healthcare ◽  
Airborne Rescue ◽  
Spread Of Infection ◽  
Saving Measure ◽  
First Time

Introduction: The coronavirus disease 2019 (COVID-19) pandemic has affected the whole world including many healthcare workers. In this era of ongoing global pandemic, the patient surge for aeromedical evacuation is going to increase. Case Details: A 54-year, male healthcare worker with no known co-morbidities, presented with complains of fever, myalgia, and sore throat at a zonal hospital of Indian Air Force in the northeast part of India. He was diagnosed with COVID-19 related bilateral extensive pneumonia. Despite of standard treatment, his condition deteriorated. An aeromedical evacuation of the patient was carried out to a tertiary healthcare centre at Delhi which involved 4-h of flying time. The Airborne Rescue Pod for Isolated Transportation (ARPIT) isolation pod was used to minimize the risk of contamination. Discussion: This was the first time that a COVID-19 patient was air evacuated in an isolation pod in Indian Armed Forces to the best of our knowledge. Based on our experience, we recommend that air evacuation of such a patient may be resorted to only as a life saving measure. The use of an isolation pod remains an unsettled issue; whereas, it gives absolute containment to spread of infection, it poses unique challenges in terms of handling the patient in case of an in-flight emergency. Certain modifications in the isolation pod have been recommended.

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