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[dinosaur] 2020 Chronostratigraphic Chart + Early Archosauromorphs + Cretaceous day length +




Ben Creisler
bcreisler@gmail.com

Some recent mainly non-dino items:


Now available:
2020 INTERNATIONAL CHRONOSTRATIGRAPHIC CHART

http://www.stratigraphy.org/index.php/ics-chart-timescale

Free pdf:

http://www.stratigraphy.org/ICSchart/ChronostratChart2020-01.pdf

News:

https://www.livescience.com/why-geolotic-time-periods.html

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MartÃn D. Ezcurra, Andrew S. Jones, Adriel R. Gentil & Richard J. Butler (2020)
Early Archosauromorphs: The Crocodile and Dinosaur Precursors.
Reference Module in Earth Systems and Environmental Sciences (2020)
doi: https://doi.org/10.1016/B978-0-12-409548-9.12439-X
https://www.sciencedirect.com/science/article/pii/B978012409548912439X?via%3Dihub


The archosauromorphs include crocodiles, dinosaurs (containing birds) and all reptiles more closely related to them than to lepidosaurs (tuataras, snakes, lizards). The oldest archosauromorphs have been collected in middle-upper Permian rocks of Europe and Africa, and the group survived the Permo-Triassic mass extinction (c. 252 million years ago), the deadliest biotic crisis documented in the fossil record. After this mass extinction, archosauromorphs diversified and became the dominant tetrapods of continental ecosystems and dispersed across the entire planet during the Triassic Period. The evolution of archosauromorphs during the Triassic is considered an example of adaptive radiation in geologic time. The non-archosaurian archosauromorphs (a group that excludes modern forms, namely crocodiles and birds, and all descendants from their most recent common ancestor) were eclipsed by the archosaur radiation in the Late Triassic, and no groups survived the Triassic-Jurassic mass extinction (c. 201 million years ago). The last decade has witnessed a renewed interest in the paleobiology of non-archosaurian archosauromorphs, and multiple advances have been made in our knowledge of these fossil reptiles. Here, we provide an updated review of the diversity, distribution, phylogeny, ecology and long-term evolution of the important but underappreciated early archosauromorph groups that flourished before the dominance of dinosaurs.

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Niels J. de Winter, ÂSteven Goderis, ÂStijn J.M. Van Malderen, ÂMatthias Sinnesael, ÂStef Vansteenberge, ÂChristophe Snoeck, ÂJoke Belza, ÂFrank Vanhaecke Â& Philippe Claeys (2020)
SubdailyâScale Chemical Variability in a Torreites Sanchezi Rudist Shell: Implications for Rudist Paleobiology and the Cretaceous DayâNight Cycle.
Paleoceanography and Paleoclimatology (advance online publication)
doi: https://doi.org/10.1029/2019PA003723
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019PA003723

Free pdf:

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019PA003723



This study presents subdaily resolved chemical records through fossil mollusk shell calcite. Trace element profiles resolve periodic variability across ~40âÎmâthin daily growth laminae in a Campanian Torreites sanchezi rudist bivalve. These highâresolution records are combined with seasonally resolved stable isotope and trace element records that allow shellâchemical variability to be discussed on both seasonal and daily scale. A combination of layer counting, spectral analysis of chemical cyclicity and chemical layer counting shows that the rudist precipitated 372 daily laminae per year, demonstrating that length of day has increased since the Late Cretaceous, as predicted by astronomical models. This new approach to determine the length of a solar day in geologic history through multiproxy chemical records at subdaily resolution yields considerably more control on the uncertainty of this estimate. Daily chemical variability exceeds seasonal variability in our records, and cannot be explained by diurnal temperature changes. Instead, we postulate that rudist shell chemistry is driven on a daily scale by changes in light intensity. These results together with those of stable isotope analyses provide strong evidence that Torreites rudists had photosymbionts. Bivalve shell calcite generally preserves well. Therefore, this study paves the way for dailyâscale reconstructions of paleoenvironment and sunlight intensity on geologic time scales from bivalve shells, potentially allowing researchers to bridge the gap between climate and weather reconstructions. Such reconstructions improve shell chronologies, document environmental change in warm ecosystems, and widen our understanding of the magnitude of shortâterm changes during greenhouse climates.

News:

Ancient shell shows days were half-hour shorter 70 million years ago

https://phys.org/news/2020-03-ancient-shell-days-half-hour-shorter.html

https://news.agu.org/press-release/ancient-shell-shows-days-were-half-hour-shorter-70-million-years-ago/

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