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Fischer Valentin - One of the best experts on this subject based on the ideXlab platform.
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Leviathans Unleashed: Skull Ecomorphological Evolution During The Initial Aquatic Radiations Of Mosasaurs And Cetaceans
2021Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to aquatic environments provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison that has received little attention is that between mosasaurs (a group of Late Cretaceous marine squamates) and early cetaceans (middle to late Eocene ancestors of modern whales and dolphins). These two groups share broad similarities in skull morphology, filling a wide range of niches and achieving global distributions. The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonising open ocean niches. Cetaceans continued to diversify after reaching this form whereas the evolutionary history of the mosasaurs was cut short by the end-Cretaceous mass extinction. Here, we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaurs and early cetaceans. These were subjected to ordination techniques to reconstruct patterns of functional ecomorphospace occupation, and putative examples of convergence were tested statistically. Preliminary results show that the earliest mosasaurs had gracile skulls, specialised for smaller prey, from which they radiated in several waves across the ecomorphospace. There is considerable variation within certain genera, such as Mosasaurus. By contrast, basilosaurid cetaceans occupy a relatively constrained megapredatory niche and cetaceans only evolved new ecomorphologies after the late Eocene split into odontocetes and mysticetes. Oligocene odontocetes explore a new area of morphospace away from the basilosaurids, evolving a long, narrow snout with an increased number of small teeth. The earliest toothed mysticetes have a similar ecomorphology to the basilosaurids, with aetiocetids appearing to radiate in a similar direction to the odontocetes. The late Oligocene Janjucetus, which has a highly unusual ecomorphology, plots away from other cetaceans. Despite showing striking similarities to the mosasaur Prognathodon (e.g short robust snout and large eyes), the two taxa were not found to be statistically convergent. However, cranial convergence was found between the mosasaur Mosasaurus hoffmanni and the basilosaurid Dorudon atrox. Future work will investigate these results using 3D landmark analyses, and the evolutionary trajectories in early mysticetes will be extrapolated by including toothless species
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Leviathans Unleashed: Skull Ecomorphological Evolution During The Initial Aquatic Radiations Of Mosasaurs And Cetaceans
2021Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to aquatic environments provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison that has received little attention is that between mosasaurs (a group of Late Cretaceous marine squamates) and early cetaceans (middle to late Eocene ancestors of modern whales and dolphins). These two groups share broad similarities in skull morphology, filling a wide range of niches and achieving global distributions. The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonising open ocean niches. Cetaceans continued to diversify after reaching this form whereas the evolutionary history of the mosasaurs was cut short by the end-Cretaceous mass extinction. Here, we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaurs and early cetaceans. These were subjected to ordination techniques to reconstruct patterns of functional ecomorphospace occupation, and putative examples of convergence were tested statistically. Preliminary results show that the earliest mosasaurs had gracile skulls, specialised for smaller prey, from which they radiated in several waves across the ecomorphospace. There is considerable variation within certain genera, such as Mosasaurus. By contrast, basilosaurid cetaceans occupy a relatively constrained megapredatory niche and cetaceans only evolved new ecomorphologies after the late Eocene split into odontocetes and mysticetes. Oligocene odontocetes explore a new area of morphospace away from the basilosaurids, evolving a long, narrow snout with an increased number of small teeth. The earliest toothed mysticetes have a similar ecomorphology to the basilosaurids, with aetiocetids appearing to radiate in a similar direction to the odontocetes. The late Oligocene Janjucetus, which has a highly unusual ecomorphology, plots away from other cetaceans. Despite showing striking similarities to the mosasaur Prognathodon (e.g short robust snout and large eyes), the two taxa were not found to be statistically convergent. However, cranial convergence was found between the mosasaur Mosasaurus hoffmanni and the basilosaurid Dorudon atrox. Future work will investigate these results using 3D landmark analyses, and the evolutionary trajectories in early mysticetes will be extrapolated by including toothless species.Peer reviewe
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Charting new waters: changes in skull ecomorphology during the initial aquatic radiations of mosasaurs and cetaceans
2020Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to water provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison which has received little attention is that of cetaceans (whales and dolphins) and mosasaurs (a group of Late Cretaceous marine squamates). The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonizing open ocean niches. Here we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaur and early cetacean. These were subjected to ordination techniques to reconstruct patterns of functional morphospace occupation. Preliminary results show that the earliest mosasaurs had gracile skulls specialized for smaller prey, from which they radiated in several waves across the morphospace. By contrast, basilosaurid cetaceans occupied a relatively constrained megapredatory niche, and only evolved new ecomorphologies after the Late Eocene split into odontocetes and mysticetes. Theresults also suggest cranial convergence between the toothed mysticete Janjucetus and the mosasaur Prognathodon. Future work will investigate these results further using 3D landmarks.Peer reviewe
Khan, Sher Afghan - One of the best experts on this subject based on the ideXlab platform.
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Simulation of effect of various distances between front and rear Body on drag of a non-circular cylinder
academia Baru, 2019Co-Authors: Sajali, Muhammad Fahmi Mohd, Aabid Abdul, Syed Ashfaq, Khan, Sher AfghanAbstract:Numerical investigation of a non-circular cylinder (D-shaped bluff Body) of fore Body, geometrical effects on the drag as well as on the flow-field were simulated at the subcritical flow regime at a velocity of 26.84 m/s. The non-circular cylinder (D-shaped model) front surface for a positive pressure of the unsteady vortex generation in the near wake, the square plate was attached upstream of the non-circular cylinder as the base model. The foreBody modifies the streamlines that separate from its edges to attach smoothly onto the front face shoulders of the main Body, thereby converting the bluff Body into an equivalent Streamlined Body, resulting in minimum drag. The height of the foreBody (B1) is 25 mm, and the length of the front Body (L2), was in the range from 0.25B2 to 1.75B2. The results obtained from the simulation are compared with the experimental results. The results indicate that the side faces and the rear faces are subjected to low pressure, whereas the front face is experiencing high positive pressure. With this flow pattern, the pressure drag coefficient assumes a substantially significant value in the range of 1.0 - 1.42. Such a high value of drag coefficient is particularly valid for bluff bodies with noncircular cross-sections with the sharp corners
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Design and fabrication of flying saucer utilizing coanda effect
'IOP Publishing', 2018Co-Authors: Aabid Abdul, Khan, Sher AfghanAbstract:Coanda effect is used in several engineering applications with distinctive designs and structures. It is also applied in aircrafts flying at low speeds for a comfortable ride. In this paper, we have designed and modelled Coanda effect in terms of a flying saucer. The fabrication was done by means of structural and electronic components. Electrical motor was used as a propeller to take off and land vertically (VTOL) along with hovering capability. The rotor disc diameter is smaller than the bulbous Body unlike a helicopter which makes to fly very stable. Control flaps were used to regulate the path by altering the flow over the Streamlined Body. The model was then tested with a remote control. Numerical Simulation of the tesla turbine was done using ANSYS 14.5 software and displacements were obtained by applying different forces on designed model. CATIA V5 was used to analyse the shaft of the model to get minimum value of torque at which the shaft starts to deform. © Published under licence by IOP Publishing Ltd
Schewe G. - One of the best experts on this subject based on the ideXlab platform.
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Reynolds-Number Effects on Bridge Aerodynamics
2004Co-Authors: Schewe G.Abstract:Long span bridges are composed of more or less bluff bodies. A main point of the lecture is the question: In which case does the Re. No. play a significant role, in particular concerning their influence on the propensity to flow induced vibrations. The paper reviews the results of experiments carried out over a wide range of Reynolds numbers ( 104 < Re < 107 ) on 2-D sections. The bodies are a circular cylinder, a bridge section, and a thick airfoil at high angle of attack. In all cases, variation of Re led to dramatic changes in the force coefficients and St. No., caused by changes in the topological structure of the separated flow. The important results are, that there are 2-D sections that behave as a bluff- or Streamlined Body, depending on Re, and that slender bodies with sharp-edged cross-sections may also suffer pronounced Re. No effects
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Reynolds-number effects in flow around more-or-less bluff bodies
2003Co-Authors: Schewe G.Abstract:The lecture reviews the results of experiments carried out over a wide range of Reynolds numbers (10^4<Re<10^7) on 2-D sections in the high-pressure wind tunnel in Göttingen. The bodies are a circular cylinder, a sharp-edged, trapezoidal-shaped bridge element, and a thick airfoil at a high attack angle. In all cases, appropriately shifting the value of Re led to dramatic changes in the force coefficients and St. No. Changes in the topological structure of the separated flow cause the observed phenomena: oil-flow pictures were used to make the phenomena visible. These events, which are triggered by the laminar/turbulent transition and its location, have characteristics that appear to be universally valid because they occur in similar form in flow over the three different bodies. The important results are (i) flow around 2-D bodies can be highly three-dimensional, (ii) there are 2-D sections that behave as a bluff- or Streamlined Body, depending on Re, and (iii) slender bodies with sharp-edged cross-sections may also suffer pronounced Reynolds number effects
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Reynolds number effects in flow around more or less bluff bodies including a bridge deck section
2002Co-Authors: Schewe G.Abstract:Long span bridges are composed of more or less bluff bodies. A main point of the lecture is the question: In which case does the Re.No. play a significant role, in particular concerning their influence on the propensity to flow induced vibrations. The paper reviews the results of experiments carried out over a wide range of Reynolds numbers (10^4<RE<10^7) on 2-D sections. The bodies are circular cylinder, a bridge section, and a thick airfoil at high angle of attack. In all cases, variation of Re led to dramatic changes in the force coefficients and St. No., caused by changes in the topological structurre of the separated flow. The important results are (i) flow around 2-D bodies can be highly three-dimensional, (ii) there are 2-D sections that behave as a bluff- or Streamlined Body, depending on Re, an (iii) slender bodies with sharp-edged cross-sections may also suffer pronounced Reynolds effects
Bennion Rebecca - One of the best experts on this subject based on the ideXlab platform.
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Leviathans Unleashed: Skull Ecomorphological Evolution During The Initial Aquatic Radiations Of Mosasaurs And Cetaceans
2021Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to aquatic environments provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison that has received little attention is that between mosasaurs (a group of Late Cretaceous marine squamates) and early cetaceans (middle to late Eocene ancestors of modern whales and dolphins). These two groups share broad similarities in skull morphology, filling a wide range of niches and achieving global distributions. The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonising open ocean niches. Cetaceans continued to diversify after reaching this form whereas the evolutionary history of the mosasaurs was cut short by the end-Cretaceous mass extinction. Here, we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaurs and early cetaceans. These were subjected to ordination techniques to reconstruct patterns of functional ecomorphospace occupation, and putative examples of convergence were tested statistically. Preliminary results show that the earliest mosasaurs had gracile skulls, specialised for smaller prey, from which they radiated in several waves across the ecomorphospace. There is considerable variation within certain genera, such as Mosasaurus. By contrast, basilosaurid cetaceans occupy a relatively constrained megapredatory niche and cetaceans only evolved new ecomorphologies after the late Eocene split into odontocetes and mysticetes. Oligocene odontocetes explore a new area of morphospace away from the basilosaurids, evolving a long, narrow snout with an increased number of small teeth. The earliest toothed mysticetes have a similar ecomorphology to the basilosaurids, with aetiocetids appearing to radiate in a similar direction to the odontocetes. The late Oligocene Janjucetus, which has a highly unusual ecomorphology, plots away from other cetaceans. Despite showing striking similarities to the mosasaur Prognathodon (e.g short robust snout and large eyes), the two taxa were not found to be statistically convergent. However, cranial convergence was found between the mosasaur Mosasaurus hoffmanni and the basilosaurid Dorudon atrox. Future work will investigate these results using 3D landmark analyses, and the evolutionary trajectories in early mysticetes will be extrapolated by including toothless species
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Leviathans Unleashed: Skull Ecomorphological Evolution During The Initial Aquatic Radiations Of Mosasaurs And Cetaceans
2021Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to aquatic environments provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison that has received little attention is that between mosasaurs (a group of Late Cretaceous marine squamates) and early cetaceans (middle to late Eocene ancestors of modern whales and dolphins). These two groups share broad similarities in skull morphology, filling a wide range of niches and achieving global distributions. The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonising open ocean niches. Cetaceans continued to diversify after reaching this form whereas the evolutionary history of the mosasaurs was cut short by the end-Cretaceous mass extinction. Here, we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaurs and early cetaceans. These were subjected to ordination techniques to reconstruct patterns of functional ecomorphospace occupation, and putative examples of convergence were tested statistically. Preliminary results show that the earliest mosasaurs had gracile skulls, specialised for smaller prey, from which they radiated in several waves across the ecomorphospace. There is considerable variation within certain genera, such as Mosasaurus. By contrast, basilosaurid cetaceans occupy a relatively constrained megapredatory niche and cetaceans only evolved new ecomorphologies after the late Eocene split into odontocetes and mysticetes. Oligocene odontocetes explore a new area of morphospace away from the basilosaurids, evolving a long, narrow snout with an increased number of small teeth. The earliest toothed mysticetes have a similar ecomorphology to the basilosaurids, with aetiocetids appearing to radiate in a similar direction to the odontocetes. The late Oligocene Janjucetus, which has a highly unusual ecomorphology, plots away from other cetaceans. Despite showing striking similarities to the mosasaur Prognathodon (e.g short robust snout and large eyes), the two taxa were not found to be statistically convergent. However, cranial convergence was found between the mosasaur Mosasaurus hoffmanni and the basilosaurid Dorudon atrox. Future work will investigate these results using 3D landmark analyses, and the evolutionary trajectories in early mysticetes will be extrapolated by including toothless species.Peer reviewe
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Charting new waters: changes in skull ecomorphology during the initial aquatic radiations of mosasaurs and cetaceans
2020Co-Authors: Bennion Rebecca, Maclaren James, Coombs Ellen, Marx Felix, Lambert Olivier, Fischer ValentinAbstract:The repeated return of tetrapods to water provides many iconic examples of convergent evolution, with various groups of mammals and reptiles independently evolving Streamlined Body shapes and similar feeding strategies. One comparison which has received little attention is that of cetaceans (whales and dolphins) and mosasaurs (a group of Late Cretaceous marine squamates). The earliest fully aquatic members of both groups had serpentine bodies and swam by axial undulation, before evolving more efficient caudal oscillatory locomotion and colonizing open ocean niches. Here we investigate possible parallel evolutionary trajectories of skull morphology that occurred during these initial aquatic radiations. A series of functionally informative ratios were calculated from 32 species of mosasaur and early cetacean. These were subjected to ordination techniques to reconstruct patterns of functional morphospace occupation. Preliminary results show that the earliest mosasaurs had gracile skulls specialized for smaller prey, from which they radiated in several waves across the morphospace. By contrast, basilosaurid cetaceans occupied a relatively constrained megapredatory niche, and only evolved new ecomorphologies after the Late Eocene split into odontocetes and mysticetes. Theresults also suggest cranial convergence between the toothed mysticete Janjucetus and the mosasaur Prognathodon. Future work will investigate these results further using 3D landmarks.Peer reviewe
Nicolas Martin - One of the best experts on this subject based on the ideXlab platform.
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adaptation and acclimation of traits associated with swimming capacity in lake whitefish coregonus clupeaformis ecotypes
BMC Evolutionary Biology, 2016Co-Authors: Anne C Dalziel, Nicolas Martin, Martin LaporteAbstract:Improved performance in a given ecological niche can occur through local adaptation, phenotypic plasticity, or a combination of these mechanisms. Evaluating the relative importance of these two mechanisms is needed to better understand the cause of intra specific polymorphism. In this study, we reared populations of Lake Whitefish (Coregonus clupeaformis) representing the’normal’ (benthic form) and the ‘dwarf’ (derived limnetic form) ecotypes in two different conditions (control and swim-training) to test the relative importance of adaptation and acclimation in the differentiation of traits related to swimming capacity. The dwarf whitefish is a more active swimmer than the normal ecotype, and also has a higher capacity for aerobic energy production in the swimming musculature. We hypothesized that dwarf fish would show changes in morphological and physiological traits consistent with reductions in the energetic costs of swimming and maintenance metabolism. We found differences in traits predicted to decrease the costs of prolonged swimming and standard metabolic rate and allow for a more active lifestyle in dwarf whitefish. Dwarf whitefish evolved a more Streamlined Body shape, predicted to lead to a decreased drag, and a smaller brain, which may decrease their standard metabolic rate. Contrary to predictions, we also found evidence of acclimation in liver size and metabolic enzyme activities. Results support the view that local adaptation has contributed to the genetically-based divergence of traits associated with swimming activity. Presence of post-zygotic barriers limiting gene flow between these ecotype pairs may have favoured repeated local adaptation to the limnetic niches.