Ben Creisler
Some recent papers, a few dino-related
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https://sbpbrasil.org/publications/index.php/rbp/article/view/175/48The Janner site (Upper Triassic of Southern Brazil) has been intensely explored, yielding constant new findings in recent years. Among these some fragmentary dinosaur specimens still not published were sampled. In this contribution, we describe these specimens, which represent five individuals, in order to increase our understanding on the anatomy of the dinosaurs that compose the paleofauna of the Janner site. The specimen CAPPA/UFSM 0270 is comprised of a series of six articulated presacral vertebrae, plus two isolated vertebrae associated with a right femur. UFRGS-PV-1232-T comprises a sacrum and a left ilium. CAPPA/UFSM 0271 comprises a right humerus that lacks the middle portion of the diaphysis. CAPPA/UFSM 00272 and 2073 are both comprised of an isolated femur each. The fragmentary condition of the materials hampers any less inclusive assignation. However, the morphology of the elements resembles those of coeval dinosaurs. Furthermore, the new specimens increase our knowledge on the morphology of some structures poorly understood from the dinosaurs of Janner site, such as the hindlimb and axial skeleton.
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In this paper, a shark-bitten partial tibiotarsus of a hesperornithiform bird is described from the Upper Cretaceous of Grant County, South Dakota, U.S.A. Whether the bite marks represent a predatory attack or scavenging is uncertain, but they are attributed to an anacoracid shark, Squalicorax cf. S. falcatus. The specimen is significant because it further indicates that hesperornithiform birds were common food sources for carnivores in the Late Cretaceous Western Interior Seaway of North America, and that Squalicorax was a trophic generalist.
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Fossil amniotic eggs have great informative potential, especially regarding reproductive and evolutionary aspects of vertebrates. However, there are only few intact specimens or with fossilized embryos within, and the rare reported cases are mostly related to dinosaurs. In Brazil, the records of these ichnofossils are practically restricted to the Bauru Basin. This research aims to describe the first amniotic egg found in carbonate concretions in the Romualdo Formation, adding information to the study of these fossils and to the paleontological context of the basin. The specimen was collected at the SÃtio Pà da Serra do FÃlix, in the Municipality of SimÃes, Piauà State, Brazil. The methodology employed was based on Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Optical Microscopy techniques, as well as computed tomography analyses. The morphological and microstructural characteristics of the shell suggests the identification of the fossil as a crocodylomorph egg. This specimen differs from other fossil eggs assigned to the aforementioned group by its small size and considerably thick shell. The tomographic sections revealed possible basic structures of an embryo inside the egg, suggesting that this is the first fossilized egg with a crocodylomorph embryonic trace found in the world.Â
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Samantha J. Gibbs, Paul R. Bown, Ben A. Ward, Sarah A. Alvarez, Hojung Kim, Odysseas A. Archontikis, Boris Sauterey, Alex J. Poulton, Jamie Wilson and Andy Ridgwell (2020)
Algal plankton turn to hunting to survive and recover from end-Cretaceous impact darkness.
Science Advances 6(44): eabc9123
DOI: 10.1126/sciadv.abc9123
https://advances.sciencemag.org/content/advances/6/44/eabc9123.full.pdf
The end-Cretaceous bolide impact triggered the devastation of marine ecosystems. However, the specific kill mechanism(s) are still debated, and how primary production subsequently recovered remains elusive. We used marine plankton microfossils and eco-evolutionary modeling to determine strategies for survival and recovery, finding that widespread phagotrophy (prey ingestion) was fundamental to plankton surviving the impact and also for the subsequent reestablishment of primary production. Ecological selectivity points to extreme post-impact light inhibition as the principal kill mechanism, with the marine food chain temporarily reset to a bacteria-dominated state. Subsequently, in a sunlit ocean inhabited by only rare survivor grazers but abundant small prey, it was mixotrophic nutrition (autotrophy and heterotrophy) and increasing cell sizes that enabled the eventual reestablishment of marine food webs some 2 million years later.
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To survive asteroid impact, algae learned to hunt
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David A. Kring, Martin J. Whitehouse, and Martin Schmieder (2020)
Microbial Sulfur Isotope Fractionation in the Chicxulub Hydrothermal System.
Astrobiology (advance online publication)
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https://doi.org/10.1089/ast.2020.2286https://www.liebertpub.com/doi/10.1089/ast.2020.2286Free pdf:
https://www.liebertpub.com/doi/pdf/10.1089/ast.2020.2286 Target lithologies and post-impact hydrothermal mineral assemblages in a new 1.3âkm deep core from the peak ring of the Chicxulub impact crater indicate sulfate reduction was a potential energy source for a microbial ecosystem (Kring et al.,2020). That sulfate was metabolized is confirmed here by microscopic pyrite framboids with Î34S values of -5 to -35 â and ÎSsulfate-sulfide values between pyrite and source sulfate of 25 to 54 â, which are indicative of biologic fractionation rather than inorganic fractionation processes. These data indicate the Chicxulub impact crater and its hydrothermal system hosted a subsurface microbial community in porous permeable niches within the crater's peak ring.
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A Subterranean ecosystem in the Chicxulub crater