Daran Zheng, Su-Chin Chang,, He Wang, Yan Fang, Jun Wang, Chongqing Feng, Guwei Xie, Edmund A. Jarzembowski, Haichun Zhang and Bo Wang (2018)
Middle-Late Triassic insect radiation revealed by diverse fossils and isotopic ages from China.
Science Advances 4(9) eaat1380
DOI: 10.1126/sciadv.aat1380
The Triassic represented an important period that witnessed the diversification of marine and terrestrial ecosystems. The radiations of terrestrial plants and vertebrates during this period have been widely investigated; however, the Triassic history of insects, the most diverse group of organisms on Earth, remains enigmatic because of the rarity of Early-Middle Triassic fossils. We report new insect fossils from a Ladinian deposit (Tongchuan entomofauna) dated to approximately 238 to 237 million years ago and a Carnian deposit (Karamay entomofauna) in northwestern China, including the earliest definite caddisfly cases (Trichoptera), water boatmen (Hemiptera), diverse polyphagan beetles (Coleoptera), and scorpionflies (Mecoptera). The Tongchuan entomofauna is near the Ladinian-Carnian boundary in age, providing a calibration date for correlation to contemporaneous biotas. Our findings confirm that the clade Holometabola, comprising most of the modern-day insect species, experienced extraordinary diversification in the Middle-Late Triassic. Moreover, our results suggest that the diversification of aquatic insects (a key event of the "Mesozoic Lacustrine Revolution") had already begun by the Middle Triassic, providing new insights into the early evolution of freshwater ecosystems.
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Ancient insect graveyards reveal an explosion in bug diversity 237 million years ago
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For new full issue on climate hyperthermals:
Discussion meeting issue âHyperthermals: rapid and extreme global warming in our geological pastâ compiled and edited by Gavin L. Foster, Pincelli Hull, Daniel J. Lunt and James C. Zachos.
Philosophical Transactions A 37
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Michael J. Benton (2018)
Hyperthermal-driven mass extinctions: killing models during the PermianâTriassic mass extinction.
In : Discussion meeting issue âHyperthermals: rapid and extreme global warming in our geological pastâ compiled and edited by Gavin L. Foster, Pincelli Hull, Daniel J. Lunt and James C. Zachos.
Philosophical Transactions A 376: 20170076
DOI: 10.1098/rsta.2017.0076
Free pdf:
Many mass extinctions of life in the sea and on land have been attributed to geologically rapid heating, and in the case of the Permian-Triassic and others, driven by large igneous province volcanism. The Siberian Traps eruptions raised ambient temperatures to 35-40ÂC. A key question is how massive eruptions during these events, and others, could have killed life in the sea and on land; proposed killers are reviewed here. In the oceans, benthos and plankton were killed by anoxiaâeuxinia and lethal heating, respectively, and the habitable depth zone was massively reduced. On land, the combination of extreme heating and drought reduced the habitable land area, and acid rain stripped forests and soils. Physiological experiments show that some animals can adapt to temperature rises of a few degrees, and that some can survive short episodes of increases of 10ÂC. However, most plants and animals suffer major physiological damage at temperatures of 35-40ÂC. Studies of the effects of extreme physical conditions on modern organisms, as well as assumptions about rates of environmental change, give direct evidence of likely killing effects deriving from hyperthermals of the past.
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Michael W. Broadley, Peter H. Barry, Chris J. Ballentine, Lawrence A. Taylor & Ray Burgess (2018)
End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles.
Nature Geoscience 11: 682â687 (2018)Â
Magmatic volatile release to the atmosphere can lead to climatic changes and substantial environmental degradation including the production of acid rain, ocean acidification and ozone depletion, potentially resulting in the collapse of the biosphere. The largest recorded mass extinction in Earthâs history occurred at the end of the Permian, coinciding with the emplacement of the Siberian large igneous province, suggesting that large-scale magmatism is a key driver of global environmental change. However, the source and nature of volatiles in the Siberian large igneous province remain contentious. Here we present halogen compositions of sub-continental lithospheric mantle xenoliths emplaced before and after the eruption of the Siberian flood basalts. We show that the Siberian lithosphere is massively enriched in halogens from the infiltration of subducted seawater-derived volatiles and that a considerable amount (up to 70%) of lithospheric halogens are assimilated into the plume and released to the atmosphere during emplacement. Plumeâlithosphere interaction is therefore a key process controlling the volatile content of large igneous provinces and thus the extent of environmental crises, leading to mass extinctions during their emplacement.
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Sandra Kirtland Turner (2018)
Constraints on the onset duration of the PaleoceneâEocene Thermal Maximum.
In : Discussion meeting issue âHyperthermals: rapid and extreme global warming in our geological pastâ compiled and edited by Gavin L. Foster, Pincelli Hull, Daniel J. Lunt and James C. Zachos.
Philosophical Transactions A 376: 20170082
DOI: 10.1098/rsta.2017.0082
free pdf:Â
The Paleocene-Eocene Thermal Maximum (PETM, approx. 56âMa) provides a test case for investigating how the Earth system responds to rapid greenhouse gas-driven warming. However, current rates of carbon emissions are approximately 10âPgâCâyrâ1, whereas those proposed for the PETM span orders of magnitude--from â1âPgâC yrâ1 to greater than the anthropogenic rate. Emissions rate estimates for the PETM are hampered by uncertainty over the total mass of PETM carbon released as well as the PETM onset duration. Here, I review constraints on the onset duration of the carbon isotope excursion (CIE) that is characteristic of the event with a focus on carbon cycle model-based attempts that forgo the need for a traditional sedimentary age model. I also review and compare existing PETM carbon input scenarios employing the Earth system model cGENIE and suggest another possibility--that abrupt input of an isotopically depleted carbon source combined with elevated volcanic outgassing over a longer interval can together account for key features of the PETM CIE.
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Bradley Deline, Jennifer M. Greenwood, James W. Clark, Mark N. Puttick, Kevin J. Peterson, and Philip C. J. Donoghue (2018)
Evolution of metazoan morphological disparity.
Proceedings of the National Academy of Sciences (advance online publication)
Significance
We attempt to quantify animal âbodyplansâ and their variation within Metazoa. Our results challenge the view that maximum variation was achieved early in animal evolutionary history by nonuniformitarian mechanisms. Rather, they are compatible with the view that the capacity for fundamental innovation is not limited to the early evolutionary history of clades. We perform quantitative tests of the principal hypotheses of the molecular mechanisms underpinning the establishment of animal bodyplans and corroborate the hypothesis that animal evolution has been permitted or driven by gene regulatory evolution.
Abstract
The animal kingdom exhibits a great diversity of organismal form (i.e., disparity). Whether the extremes of disparity were achieved early in animal evolutionary history or clades continually explore the limits of possible morphospace is subject to continuing debate. Here we show, through analysis of the disparity of the animal kingdom, that, even though many clades exhibit maximal initial disparity, arthropods, chordates, annelids, echinoderms, and mollusks have continued to explore and expand the limits of morphospace throughout the Phanerozoic, expanding dramatically the envelope of disparity occupied in the Cambrian. The âclumpinessâ of morphospace occupation by living clades is a consequence of the extinction of phylogenetic intermediates, indicating that the original distribution of morphologies was more homogeneous. The morphological distances between phyla mirror differences in complexity, body size, and species-level diversity across the animal kingdom. Causal hypotheses of morphologic expansion include time since origination, increases in genome size, protein repertoire, gene family expansion, and gene regulation. We find a strong correlation between increasing morphological disparity, genome size, and microRNA repertoire, but no correlation to protein domain diversity. Our results are compatible with the view that the evolution of gene regulation has been influential in shaping metazoan disparity whereas the invasion of terrestrial ecospace appears to represent an additional gestalt, underpinning the post-Cambrian expansion of metazoan disparity.
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