Ben Creisler
Some recent non-dino papers:
Ecological diversity among diurnal birds of prey, or raptors, is highlighted regarding their sensory abilities. While raptors are believed to forage primarily using sight, the sensory demands of scavengers and predators differ, as reflected in their visual systems. Here, I have reviewed the visual specialisations of predatory and scavenging diurnal raptors, focusing on (1) the anatomy of the eye and (2) the use of vision in foraging. Predators have larger eyes than scavengers relative to their body mass, potentially highlighting the higher importance of vision in these species. Scavengers possess one centrally positioned fovea that allows for the detection of carrion at a distance. In addition to the central fovea, predators have a second, temporally positioned fovea that views the frontal visual field, possibly for prey capture. Spatial resolution does not differ between predators and scavengers. In contrast, the organisation of the visual fields reflects important divergences, with enhanced binocularity in predators opposed to an enlarged field of view in scavengers. Predators also have a larger blind spot above the head. The diversity of visual system specializations according to the foraging ecology displayed by these birds suggests a complex interplay between visual anatomy and ecology, often unrelatedly of phylogeny.
Highlights
First Toarcian SST record based on molecular paleothermometry.
Highly variable SSTs attest to contrasting climate modes.
Direct coupling between SST, oxygen isotopes and sea level evolution.
Perception of an overall warm early Jurassic Greenhouse world should be discarded.
Abstract
In this paper, we use molecular paleothermometry, based on the TEX86 proxy derived from fossilized archaeal lipids, to reconstruct absolute sea surface temperatures (SSTs) for the northwest Tethys Shelf during the late Pliensbachian to early Toarcian (Early Jurassic, ~183âMa) stages. Our composite record from outcrops in Spain and Italy reveals that tropical SSTs varied between 22 and 32âÂC over aâ~â3 Myr time period, including transient temperature excursions of 5â10âÂC magnitude with lapse rates of ~0.1âÂC/kyr. Changes in reconstructed SSTs covaried with sea level fluctuations and Î18O isotope signatures of marine biocalcifiers, recording recurrent shifts between icehouse and greenhouse states. Parallel trends of reconstructed SST and Î13C isotopes of atmospheric CO2 may reflect storage of isotopically light carbon in cryosphere reservoirs during icehouse phases and release during greenhouse phases. The existence of a labile cryosphere is considered a prerequisite to explain the inferred rapid climate fluctuations and as a reservoir to facilitate pronounced carbon isotope excursions.
Big, beautiful organisms are useful for biological education, increasing evolution literacy, and biodiversity conservation. But if educators gloss over the ubiquity of streamlined and miniaturized organisms, they unwittingly leave students and the public vulnerable to the idea that the primary evolutionary plot of every metazoan lineage is "progressive" and "favors" complexity. We show that simple, small, and intriguingly repulsive invertebrate animals provide a counterpoint to misconceptions about evolution. Our examples can be immediately deployed in biology courses and outreach. This context emphasizes that chordates are not the pinnacle of evolution. Rather, in the evolution of animals, miniaturization, trait loss, and lack of perfection are at least as frequent as their opposites. Teaching about invertebrate animals in a "tree thinking" context uproots evolution misconceptions (for students and the public alike), provides a mental scaffold for understanding all animals, and helps to cultivate future ambassadors and experts on these littleâknown, weird, and fascinating taxa.
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Free pdf:
Jason D. Pardo, Kendra Lennie and Jason S. Anderson (2020)
Can We Reliably Calibrate Deep Nodes in the Tetrapod Tree? Case Studies in Deep Tetrapod Divergences.
Frontiers in Genetics 11:506749.
doi: https://doi.org/10.3389/fgene.2020.506749
https://www.frontiersin.org/articles/10.3389/fgene.2020.506749/full
Recent efforts have led to the development of extremely sophisticated methods for incorporating tree-wide data and accommodating uncertainty when estimating the temporal patterns of phylogenetic trees, but assignment of prior constraints on node age remains the most important factor. This depends largely on understanding substantive disagreements between specialists (paleontologists, geologists, and comparative anatomists), which are often opaque to phylogeneticists and molecular biologists who rely on these data as downstream users. This often leads to misunderstandings of how the uncertainty associated with node age minima arises, leading to inappropriate treatments of that uncertainty by phylogeneticists. In order to promote dialogue on this subject, we here review factors (phylogeny, preservational megabiases, spatial and temporal patterns in the tetrapod fossil record) that complicate assignment of prior node age constraints for deep divergences in the tetrapod tree, focusing on the origin of crown-group Amniota, crown-group Amphibia, and crown-group Tetrapoda. We find that node priors for amphibians and tetrapods show high phylogenetic lability and different phylogenetic treatments identifying disparate taxa as the earliest representatives of these crown groups. This corresponds partially to the well-known problem of lissamphibian origins but increasingly reflects deeper instabilities in early tetrapod phylogeny. Conversely, differences in phylogenetic treatment do not affect our ability to recognize the earliest crown-group amniotes but do affect how diverse we understand the earliest amniote faunas to be. Preservational megabiases and spatiotemporal heterogeneity of the early tetrapod fossil record present unrecognized challenges in reliably estimating the ages of tetrapod nodes; the tetrapod record throughout the relevant interval is spatially restricted and disrupted by several major intervals of minimal sampling coincident with the emergence of all three crown groups. Going forward, researchers attempting to calibrate the ages for these nodes, and other similar deep nodes in the metazoan fossil record, should consciously consider major phylogenetic uncertainty, preservational megabias, and spatiotemporal heterogeneity, preferably examining the impact of working hypotheses from multiple research groups. We emphasize a need for major tetrapod collection effort outside of classic European and North American sections, particularly from the southern hemisphere, and suggest that such sampling may dramatically change our timelines of tetrapod evolution.
Can We Reliably Calibrate Deep Nodes in the Tetrapod Tree? Case Studies in Deep Tetrapod Divergences.
Frontiers in Genetics 11:506749.
doi: https://doi.org/10.3389/fgene.2020.506749
https://www.frontiersin.org/articles/10.3389/fgene.2020.506749/full
Recent efforts have led to the development of extremely sophisticated methods for incorporating tree-wide data and accommodating uncertainty when estimating the temporal patterns of phylogenetic trees, but assignment of prior constraints on node age remains the most important factor. This depends largely on understanding substantive disagreements between specialists (paleontologists, geologists, and comparative anatomists), which are often opaque to phylogeneticists and molecular biologists who rely on these data as downstream users. This often leads to misunderstandings of how the uncertainty associated with node age minima arises, leading to inappropriate treatments of that uncertainty by phylogeneticists. In order to promote dialogue on this subject, we here review factors (phylogeny, preservational megabiases, spatial and temporal patterns in the tetrapod fossil record) that complicate assignment of prior node age constraints for deep divergences in the tetrapod tree, focusing on the origin of crown-group Amniota, crown-group Amphibia, and crown-group Tetrapoda. We find that node priors for amphibians and tetrapods show high phylogenetic lability and different phylogenetic treatments identifying disparate taxa as the earliest representatives of these crown groups. This corresponds partially to the well-known problem of lissamphibian origins but increasingly reflects deeper instabilities in early tetrapod phylogeny. Conversely, differences in phylogenetic treatment do not affect our ability to recognize the earliest crown-group amniotes but do affect how diverse we understand the earliest amniote faunas to be. Preservational megabiases and spatiotemporal heterogeneity of the early tetrapod fossil record present unrecognized challenges in reliably estimating the ages of tetrapod nodes; the tetrapod record throughout the relevant interval is spatially restricted and disrupted by several major intervals of minimal sampling coincident with the emergence of all three crown groups. Going forward, researchers attempting to calibrate the ages for these nodes, and other similar deep nodes in the metazoan fossil record, should consciously consider major phylogenetic uncertainty, preservational megabias, and spatiotemporal heterogeneity, preferably examining the impact of working hypotheses from multiple research groups. We emphasize a need for major tetrapod collection effort outside of classic European and North American sections, particularly from the southern hemisphere, and suggest that such sampling may dramatically change our timelines of tetrapod evolution.
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Free pdf:
Simon Potier (2020)
Visual Adaptations in Predatory and Scavenging Diurnal Raptors.
Diversity 12(10): 400
doi: https://doi.org/10.3390/d12100400
https://www.mdpi.com/1424-2818/12/10/400
Visual Adaptations in Predatory and Scavenging Diurnal Raptors.
Diversity 12(10): 400
doi: https://doi.org/10.3390/d12100400
https://www.mdpi.com/1424-2818/12/10/400
Ecological diversity among diurnal birds of prey, or raptors, is highlighted regarding their sensory abilities. While raptors are believed to forage primarily using sight, the sensory demands of scavengers and predators differ, as reflected in their visual systems. Here, I have reviewed the visual specialisations of predatory and scavenging diurnal raptors, focusing on (1) the anatomy of the eye and (2) the use of vision in foraging. Predators have larger eyes than scavengers relative to their body mass, potentially highlighting the higher importance of vision in these species. Scavengers possess one centrally positioned fovea that allows for the detection of carrion at a distance. In addition to the central fovea, predators have a second, temporally positioned fovea that views the frontal visual field, possibly for prey capture. Spatial resolution does not differ between predators and scavengers. In contrast, the organisation of the visual fields reflects important divergences, with enhanced binocularity in predators opposed to an enlarged field of view in scavengers. Predators also have a larger blind spot above the head. The diversity of visual system specializations according to the foraging ecology displayed by these birds suggests a complex interplay between visual anatomy and ecology, often unrelatedly of phylogeny.
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Free pdf:
Wolfgang Ruebsam, ÂMatias Reolid, Nadia Sabatino, Daniele Masetti & Lorenz Schwark (2020)
Molecular paleothermometry of the early Toarcian climate perturbation.
Global and Planetary Change 103351 (advance online publication)
doi: https://doi.org/10.1016/j.gloplacha.2020.103351
https://www.sciencedirect.com/science/article/pii/S0921818120302423
Molecular paleothermometry of the early Toarcian climate perturbation.
Global and Planetary Change 103351 (advance online publication)
doi: https://doi.org/10.1016/j.gloplacha.2020.103351
https://www.sciencedirect.com/science/article/pii/S0921818120302423
Highlights
First Toarcian SST record based on molecular paleothermometry.
Highly variable SSTs attest to contrasting climate modes.
Direct coupling between SST, oxygen isotopes and sea level evolution.
Perception of an overall warm early Jurassic Greenhouse world should be discarded.
Abstract
In this paper, we use molecular paleothermometry, based on the TEX86 proxy derived from fossilized archaeal lipids, to reconstruct absolute sea surface temperatures (SSTs) for the northwest Tethys Shelf during the late Pliensbachian to early Toarcian (Early Jurassic, ~183âMa) stages. Our composite record from outcrops in Spain and Italy reveals that tropical SSTs varied between 22 and 32âÂC over aâ~â3 Myr time period, including transient temperature excursions of 5â10âÂC magnitude with lapse rates of ~0.1âÂC/kyr. Changes in reconstructed SSTs covaried with sea level fluctuations and Î18O isotope signatures of marine biocalcifiers, recording recurrent shifts between icehouse and greenhouse states. Parallel trends of reconstructed SST and Î13C isotopes of atmospheric CO2 may reflect storage of isotopically light carbon in cryosphere reservoirs during icehouse phases and release during greenhouse phases. The existence of a labile cryosphere is considered a prerequisite to explain the inferred rapid climate fluctuations and as a reservoir to facilitate pronounced carbon isotope excursions.
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Michael T. Whalen, Sean P.S. Gulick, Christopher M. Lowery, Timothy J. Bralower, Joanna V. Morgan, Kliti Grice, Bettina Schaefer, Jan Smith Jens OrmÃ, Axel Wittmann, David A. Kring, Shelby Lyons & Steven Goderis (2020)
Winding down the Chicxulub impact: The transition between impact and normal marine sedimentation near ground zero.
Marine Geology 106368 (advance online publication)
doi: https://doi.org/10.1016/j.margeo.2020.106368
https://www.sciencedirect.com/science/article/abs/pii/S0025322720302565
Winding down the Chicxulub impact: The transition between impact and normal marine sedimentation near ground zero.
Marine Geology 106368 (advance online publication)
doi: https://doi.org/10.1016/j.margeo.2020.106368
https://www.sciencedirect.com/science/article/abs/pii/S0025322720302565
The Chicxulub impact led to the formation of aâ~â200-km wide by ~1-km deep crater on MÃxico's YucatÃn Peninsula. Over a period of hours after the impact the ocean re-entered and covered the impact basin beneath several hundred meters of water. A suite of impactites were deposited across the crater during crater formation, and by the resurge, tsunami and seiche events that followed. International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub crater, and recovered ~130âm of impact deposits and a 75-cm thick, fine-grained, carbonate-rich âTransitional Unitâ, above which normal marine sedimentation resumed. Here, we describe the results of analyses of the uppermost impact breccia (suevite) and the Transitional Unit, which suggests a gradual waning of energy recorded by this local K-Pg boundary sequence.
The dominant depositional motif in the upper suevite and the Transitional Unit is of rapid sedimentation characterized by graded bedding, local cross bedding, and evidence of oscillatory currents. The lower Transitional Unit records the change from deposition of dominantly sand-sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward. The middle part of the Transitional Unit is interrupted by a 20âcm thick soft sediment slump overlain by graded and oscillatory current cross-laminated beds. The uppermost Transitional Unit is also soft sediment deformed, contains trace fossils, and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors. The Transitional Unit, as with similar deposits in other marine target impact craters, records the final phases of impact-related sedimentation prior to resumption of normal marine conditions. Petrographic and stable isotopic analyses of carbon from organic matter provide insight into post-impact processes. Î13Corg values are between terrestrial and marine end members with fluctuations of 1â3â.
Timing of deposition of the Transitional Unit is complicated to ascertain. The repetitive normally graded laminae, both below and above the soft sediment deformed interval, record rapid deposition from currents driven by tsunami and seiches, processes that likely operated for weeks to potentially years post-impact due to subsequent continental margin collapse events. Highly siderophile element-enrichment at the top of the unit is likely from fine-grained ejecta that circulated in the atmosphere for several years prior to settling. The Transitional Unit is thus an exquisite record of the final phases of impact-related sedimentation related to one of the most consequential events in Earth history.
The dominant depositional motif in the upper suevite and the Transitional Unit is of rapid sedimentation characterized by graded bedding, local cross bedding, and evidence of oscillatory currents. The lower Transitional Unit records the change from deposition of dominantly sand-sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward. The middle part of the Transitional Unit is interrupted by a 20âcm thick soft sediment slump overlain by graded and oscillatory current cross-laminated beds. The uppermost Transitional Unit is also soft sediment deformed, contains trace fossils, and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors. The Transitional Unit, as with similar deposits in other marine target impact craters, records the final phases of impact-related sedimentation prior to resumption of normal marine conditions. Petrographic and stable isotopic analyses of carbon from organic matter provide insight into post-impact processes. Î13Corg values are between terrestrial and marine end members with fluctuations of 1â3â.
Timing of deposition of the Transitional Unit is complicated to ascertain. The repetitive normally graded laminae, both below and above the soft sediment deformed interval, record rapid deposition from currents driven by tsunami and seiches, processes that likely operated for weeks to potentially years post-impact due to subsequent continental margin collapse events. Highly siderophile element-enrichment at the top of the unit is likely from fine-grained ejecta that circulated in the atmosphere for several years prior to settling. The Transitional Unit is thus an exquisite record of the final phases of impact-related sedimentation related to one of the most consequential events in Earth history.
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And a reminder about the importance of invertebrates in teaching evolution...
Free pdf:
Jesse E. CzekanskiâMoir & Rebecca J. Rundell (2020)
Endless forms most stupid, icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life.
Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1002/ece3.6892
https://onlinelibrary.wiley.com/doi/10.1002/ece3.6892
Jesse E. CzekanskiâMoir & Rebecca J. Rundell (2020)
Endless forms most stupid, icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life.
Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1002/ece3.6892
https://onlinelibrary.wiley.com/doi/10.1002/ece3.6892
Big, beautiful organisms are useful for biological education, increasing evolution literacy, and biodiversity conservation. But if educators gloss over the ubiquity of streamlined and miniaturized organisms, they unwittingly leave students and the public vulnerable to the idea that the primary evolutionary plot of every metazoan lineage is "progressive" and "favors" complexity. We show that simple, small, and intriguingly repulsive invertebrate animals provide a counterpoint to misconceptions about evolution. Our examples can be immediately deployed in biology courses and outreach. This context emphasizes that chordates are not the pinnacle of evolution. Rather, in the evolution of animals, miniaturization, trait loss, and lack of perfection are at least as frequent as their opposites. Teaching about invertebrate animals in a "tree thinking" context uproots evolution misconceptions (for students and the public alike), provides a mental scaffold for understanding all animals, and helps to cultivate future ambassadors and experts on these littleâknown, weird, and fascinating taxa.
======