Browsing by Author "Knoll, Andrew H."

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    Biomineralization by particle attachment in early animals
    Gilbert, Pupa U. P. A.; Porter, Susannah M.; Sun, Chang-Yu; Xiao, Shuhai; Gibson, Brandt M.; Shenkar, Noa; Knoll, Andrew H. (National Academy of Sciences, 2019-08-19)
    Crystallization by particle attachment (CPA) of amorphous precursors has been demonstrated in modern biomineralized skeletons across a broad phylogenetic range of animals. Precisely the same precursors, hydrated (ACC-H₂O) and anhydrous calcium carbonate (ACC), have been observed spectromicroscopically in echinoderms, mollusks, and cnidarians, phyla drawn from the 3 major clades of eumetazoans. Scanning electron microscopy (SEM) here also shows evidence of CPA in tunicate chordates. This is surprising, as species in these clades have no common ancestor that formed a mineralized skeleton and appear to have evolved carbonate biomineralization independently millions of years after their late Neoproterozoic divergence. Here we correlate the occurrence of CPA from ACC precursor particles with nanoparticulate fabric and then use the latter to investigate the antiquity of the former. SEM images of early biominerals from Ediacaran and Cambrian shelly fossils show that these early calcifiers used attachment of ACC particles to form their biominerals. The convergent evolution of biomineral CPA may have been dictated by the same thermodynamics and kinetics as we observe today.
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    Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish
    Dahl, Tais W.; Hammarlund, Emma U.; Anbar, Ariel D.; Bond, David P. G.; Gill, Benjamin C.; Gordon, Gwyneth W.; Knoll, Andrew H.; Nielsen, Arne T.; Schovsbo, Niels H.; Canfield, Donald E. (National Academy of Sciences, 2010)
    The evolution of Earth's biota is intimately linked to the oxygenation of the oceans and atmosphere. We use the isotopic composition and concentration of molybdenum (Mo) in sedimentary rocks to explore this relationship. Our results indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna, including large, motile bilaterian animals, ca. 550-560 million year ago (Ma), reinforcing previous geochemical indications that Earth surface oxygenation facilitated this radiation. The second, perhaps larger, oxygenation took place around 400 Ma, well after the initial rise of animals and, therefore, suggesting that early metazoans evolved in a relatively low oxygen environment. This later oxygenation correlates with the diversification of vascular plants, which likely contributed to increased oxygenation through the enhanced burial of organic carbon in sediments. It also correlates with a pronounced radiation of large predatory fish, animals with high oxygen demand. We thereby couple the redox history of the atmosphere and oceans to major events in animal evolution.
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    A new Early Jurassic (ca. 183 Ma) fossil Lagerstatte from Ya Ha Tinda, Alberta, Canada
    Martindale, Rowan C.; Them, Theodore R.; Gill, Benjamin C.; Marroquin, Selva M.; Knoll, Andrew H. (Geological Society of America, 2017-03-01)
    Lagerstatten-deposits of exceptionally preserved fossils-offer vital insights into evolutionary history. To date, only three Konservat Lagerstatten are known from Early Jurassic marine rocks (Osteno, Posidonia Shale, and Strawberry Bank), all located in Europe. We report a new assemblage of exceptionally preserved fossils from Alberta, Canada, the first marine Konservat-Lagerstatte described from the Jurassic of North America. The Ya Ha Tinda assemblage includes articulated vertebrates (fish, ichthyosaurs), crinoids, crustaceans, brachiopods, abundant mollusks (coleoids with soft tissues, ammonites, gastropods, bivalves), wood, and microfossils. Paired bio-and chemostratigraphies show that Lagerstatte deposition occurred during the late Pliensbachian through early Toarcian, capturing the carbon isotope excursion associated with the Toarcian Oceanic Anoxic Event. Therefore, the Panthalassan Ya Ha Tinda biota is coeval with Toarcian Lagerstatten from the Tethys Ocean (Posidonia Shale and Strawberry Bank). Comparisons among these deposits permit new insights into the diversity, ecology, and biogeography of Jurassic marine communities during a time of pronounced biological and environmental change (e.g., expanded subsurface anoxia, warming, and extinctions). They also highlight the possibility that Mesozoic Oceanic Anoxic Events are temporal foci of exceptional preservation.
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    Ordovician origin and subsequent diversification of the brown algae
    Choi, Seok-Wan; Graf, Louis; Choi, Ji Won; Jo, Jihoon; Boo, Ga Hun; Kawai, Hiroshi; Choi, Chang Geun; Xiao, Shuhai; Knoll, Andrew H.; Andersen, Robert A.; Yoon, Hwan Su (Elsevier, 2024-01-19)
    Brown algae are the only group of heterokont protists exhibiting complex multicellularity. Since their origin, brown algae have adapted to various marine habitats, evolving diverse thallus morphologies and gamete types. However, the evolutionary processes behind these transitions remain unclear due to a lack of a robust phylogenetic framework and problems with time estimation. To address these issues, we employed plastid genome data from 138 species, including heterokont algae, red algae, and other red-derived algae. Based on a robust phylogeny and new interpretations of algal fossils, we estimated the geological times for brown algal origin and diversification. The results reveal that brown algae first evolved true multicellularity, with plasmodesmata and reproductive cell differentiation, during the late Ordovician Period (ca. 450 Ma), coinciding with a major diversification of marine fauna (the Great Ordovician Biodiversification Event) and a proliferation of multicellular green algae. Despite its early Paleozoic origin, the diversification of major orders within this brown algal clade accelerated only during the Mesozoic Era, coincident with both Pangea rifting and the diversification of other heterokont algae (e.g., diatoms), coccolithophores, and dinoflagellates, with their red algal-derived plastids. The transition from ancestral isogamy to oogamy was followed by three simultaneous reappearances of isogamy during the Cretaceous Period. These are concordant with a positive character correlation between parthenogenesis and isogamy. Our new brown algal timeline, combined with a knowledge of past environmental conditions, shed new light on brown algal diversification and the intertwined evolution of multicellularity and sexual reproduction.
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    The Sedimentary Geochemistry and Paleoenvironments Project
    Farrell, Una C.; Samawi, Rifaat; Anjanappa, Savitha; Klykov, Roman; Adeboye, Oyeleye O.; Agic, Heda; Ahm, Anne-Sofie C.; Boag, Thomas H.; Bowyer, Fred; Brocks, Jochen J.; Brunoir, Tessa N.; Canfield, Donald E.; Chen, Xiaoyan; Cheng, Meng; Clarkson, Matthew O.; Cole, Devon B.; Cordie, David R.; Crockford, Peter W.; Cui, Huan; Dahl, Tais W.; Mouro, Lucas D.; Dewing, Keith; Dornbos, Stephen Q.; Drabon, Nadja; Dumoulin, Julie A.; Emmings, Joseph F.; Endriga, Cecilia R.; Fraser, Tiffani A.; Gaines, Robert R.; Gaschnig, Richard M.; Gibson, Timothy M.; Gilleaudeau, Geoffrey J.; Gill, Benjamin C.; Goldberg, Karin; Guilbaud, Romain; Halverson, Galen P.; Hammarlund, Emma U.; Hantsoo, Kalev G.; Henderson, Miles A.; Hodgskiss, Malcolm SW W.; Horner, Tristan J.; Husson, Jon M.; Johnson, Benjamin; Kabanov, Pavel; Brenhin Keller, C.; Kimmig, Julien; Kipp, Michael A.; Knoll, Andrew H.; Kreitsmann, Timmu; Kunzmann, Marcus; Kurzweil, Florian; LeRoy, Matthew A.; Li, Chao; Lipp, Alex G.; Loydell, David K.; Lu, Xinze; Macdonald, Francis A.; Magnall, Joseph M.; Mand, Kaarel; Mehra, Akshay; Melchin, Michael J.; Miller, Austin J.; Mills, N. Tanner; Mwinde, Chiza N.; O'Connell, Brennan; Och, Lawrence M.; Ossa Ossa, Frantz; Pages, Anais; Paiste, Kart; Partin, Camille A.; Peters, Shanan E.; Petrov, Peter; Playter, Tiffany L.; Plaza-Torres, Stephanie; Porter, Susannah M.; Poulton, Simon W.; Pruss, Sara B.; Richoz, Sylvain; Ritzer, Samantha R.; Rooney, Alan D.; Sahoo, Swapan K.; Schoepfer, Shane D.; Sclafani, Judith A.; Shen, Yanan; Shorttle, Oliver; Slotznick, Sarah P.; Smith, Emily F.; Spinks, Sam; Stockey, Richard G.; Strauss, Justin V.; Stueken, Eva E.; Tecklenburg, Sabrina; Thomson, Danielle; Tosca, Nicholas J.; Uhlein, Gabriel J.; Vizcaino, Maoli N.; Wang, Huajian; White, Tristan; Wilby, Philip R.; Woltz, Christina R.; Wood, Rachel A.; Xiang, Lei; Yurchenko, Inessa A.; Zhang, Tianran; Planavsky, Noah J.; Lau, Kimberly V.; Johnston, David T.; Sperling, Erik A. (Wiley, 2021-07-05)