• Discovery of ancient plant fossils in Wa

    From ScienceDaily@1:317/3 to All on Tue Feb 15 21:30:40 2022
    Discovery of ancient plant fossils in Washington points to paleobotanic mystery

    Date:
    February 15, 2022
    Source:
    University of Kansas
    Summary:
    A new description of two well-preserved ancient fossil plant
    specimens in Washington state is prompting paleobotanists to rethink
    how plants might have been dispersed during the Late Cretaceous,
    between 66 and 100 million years ago.



    FULL STORY ==========================================================================
    A new description of two well-preserved ancient fossil plant specimens
    in Washington state is prompting paleobotanists to rethink how plants
    might have been dispersed during the Late Cretaceous, between 66 and
    100 million years ago.


    ========================================================================== Research published in New Phytologistdetails two fossil winged fruits
    from the genus Ceratopetalum -- previously believed to be limited in
    range to the Southern Hemisphere during the Cretaceous. Yet these new
    fossils were found on Sucia Island in Washington state. The surprising discovery is causing paleobotanists to reconsider how extended their
    range may have truly been and how it may have occurred.

    "In this paper, we were looking at two fossil fruits we had assigned
    to the genus Ceratopetalum, which is in the flowering-plant family Cunoniaceae," said lead author Keana Tang, doctoral student in ecology & evolutionary biology at the University of Kansas and the KU Biodiversity Institute and Natural History Museum. "Both the family Cunoniaceae and the genus Ceratopetalum still have living members today. What's interesting is
    the genus Ceratopetalum is now only found in Australia. Well, the entire
    family is restricted to the Southern Hemisphere -- so it's weird to find
    this fossil all the way up here in the Northern Hemisphere. We thought,
    'Whoa, how did this get here?'" Tang and her collaborators dubbed the
    new fossil species Ceratopetalum suciensis after the island in Washington
    where they were discovered.

    Today, modern versions of the genus Ceratopetalum prevail in the wet
    tropical rainforests of Australia, where they play a vital role to
    ecosystems.

    "You'll find forests that are just dominated by these species," Tang said.



    ==========================================================================
    But she said the findings are made more significant because Ceratopetalum
    and the larger family Cunoniaceae are part of "Paleo-Antarctic Rainforest Lineages," or PARLs -- plants thought to have originated in the ancient Gondwanan landmass before spreading northward. So, a better understanding
    of how Ceratopetalum extended its range could better inform scientists
    how a key larger group of plants widened its range through geologic time.

    "They have a joint history where they were likely around Antarctica
    and spread northward as time progressed and tectonic plates changed,
    causing the climate to change. As Antarctica is getting colder, these
    plants are moving up to South America, South Africa and Australia,"
    Tang said. "It's interesting because the Paleo-Antarctic Rainforest
    Lineages are all expected to have a southern origin.

    Now that we have this record of a fruit in the Northern Hemisphere,
    it's bringing up new questions. Was the family Cunoniaceae actually cosmopolitan - - were they found everywhere? Or was this just kind of a
    lucky chance, where it somehow transported northwards through an exchange
    from the Antarctic to South America to North America?" According to
    Tang's KU adviser and co-author, Brian Atkinson, assistant professor
    of ecology & evolutionary biology and curator with the Biodiversity
    Institute's Division of Paleobotany, the findings highlight new
    possibilities for a biotic exchange between North America and South America-Antarctica that may have occurred during the Late Cretaceous.

    "In some ways this is like finding a penguin in North America," he said.

    The Ceratopetalum suciensis fossils were collected on Sucia Island by
    fossil hunters David Starr and Jim Goedert, then Micro-CT-scanned at
    the University of Michigan by co-author Selena Smith. Then, to classify
    them with the utmost accuracy, Tang analyzed them layer by layer using
    a painstaking process called the cellulose acetate peeling technique.



    ==========================================================================
    "I started peeling the rock," she said. "Essentially what's happening is
    you take the rock face and there's a series of steps where you polish the
    face of the fossil and dip it into 5% hydrochloric acid for a couple of seconds. It's very safe -- you can even dip your hands in the acid, and
    you will still have your fingertips. So, you dip it into the acid for a
    few seconds, and then you rinse the rock off with water. Then you rinse it
    with acetone, and you get this plastic sheet. That's the cellulose acetate sheet. Next, you spray the fossil face with the acetone again and then
    lay the sheet down -- and that entire process gives you a very, very thin section of the rock, a few micrometers. But it's nice because you can go through the entire fossil and pick up different structures hiding in the
    rock matrix you might miss in a Micro-CT scan." Through these processes,
    Tang was able to place the fossils in the genus Ceratopetalum and raise
    new questions about how plants spread millions of years ago. Additionally,
    the research suggests the Pacific Northwest, where Ceratopetalum suciensis
    was discovered, is a promising region for further work by paleobotanists.

    "There's just so much to look into, especially in the Western coast of
    North America," Tang said. "I understand there's just not a lot of people
    there doing that kind of work. It's relatively understudied. I think a
    lot of the paleobotanic world has been situated along the East Coast or
    the Western interior." The paper in New Phytologist represents Tang's
    first authorship on a study in a peer-reviewed journal and her first
    time as a lead author. She grew up in the suburbs north of Los Angeles
    and came to KU after meeting Atkinson and learning about his work when
    she was an intern at the Natural History Museum of Los Angeles.

    Once Tang earns her doctorate, her ambition is to continue making
    discoveries as a researcher.

    ========================================================================== Story Source: Materials provided by University_of_Kansas. Note: Content
    may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Keana K. Tang, Selena Y. Smith, Brian A. Atkinson. Extending beyond
    Gondwana: Cretaceous Cunoniaceae from western North America. New
    Phytologist, 2022; DOI: 10.1111/nph.17976 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220215113411.htm

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