• Crab in amber

    From Pandora@21:1/5 to All on Wed Oct 20 20:32:50 2021
    Crab in amber reveals an early colonization of nonmarine environments
    during the Cretaceous.

    Abstract

    Amber fossils provide snapshots of the anatomy, biology, and ecology
    of extinct organisms that are otherwise inaccessible. The best-known
    fossils in amber are terrestrial arthropods—principally
    insects—whereas aquatic organisms are rarely represented. Here, we
    present the first record of true crabs (Brachyura) in amber—from the
    Cretaceous of Myanmar [~100 to 99 million years (Ma)]. The new fossil
    preserves large compound eyes, delicate mouthparts, and even gills.
    This modern-looking crab is nested within crown Eubrachyura, or
    “higher” true crabs, which includes the majority of brachyuran species
    living today. The fossil appears to have been trapped in a brackish or freshwater setting near a coastal to fluvio-estuarine environment,
    bridging the gap between the predicted molecular divergence of
    nonmarine crabs (~130 Ma) and their younger fossil record (latest
    Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable
    calibration point for molecular divergence time estimates for higher
    crown eubrachyurans.

    Open access:
    https://www.science.org/doi/10.1126/sciadv.abj5689

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  • From Glenn@21:1/5 to Pandora on Wed Oct 20 15:33:41 2021
    On Wednesday, October 20, 2021 at 11:32:54 AM UTC-7, Pandora wrote:
    Crab in amber reveals an early colonization of nonmarine environments
    during the Cretaceous.

    Abstract

    Amber fossils provide snapshots of the anatomy, biology, and ecology
    of extinct organisms that are otherwise inaccessible. The best-known
    fossils in amber are terrestrial arthropods—principally
    insects—whereas aquatic organisms are rarely represented. Here, we
    present the first record of true crabs (Brachyura) in amber—from the Cretaceous of Myanmar [~100 to 99 million years (Ma)]. The new fossil preserves large compound eyes, delicate mouthparts, and even gills.
    This modern-looking crab is nested within crown Eubrachyura, or
    “higher” true crabs, which includes the majority of brachyuran species living today. The fossil appears to have been trapped in a brackish or freshwater setting near a coastal to fluvio-estuarine environment,


    Why would that evidence that the crab was in a nonmarine environment?

    bridging the gap between the predicted molecular divergence of
    nonmarine crabs (~130 Ma) and their younger fossil record (latest
    Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable calibration point for molecular divergence time estimates for higher
    crown eubrachyurans.

    Open access:
    https://www.science.org/doi/10.1126/sciadv.abj5689

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  • From Pandora@21:1/5 to All on Fri Oct 22 17:09:13 2021
    On Wed, 20 Oct 2021 15:33:41 -0700 (PDT), Glenn <GlennSheldon@msn.com>
    wrote:

    On Wednesday, October 20, 2021 at 11:32:54 AM UTC-7, Pandora wrote:
    Crab in amber reveals an early colonization of nonmarine environments
    during the Cretaceous.

    Abstract

    Amber fossils provide snapshots of the anatomy, biology, and ecology
    of extinct organisms that are otherwise inaccessible. The best-known
    fossils in amber are terrestrial arthropods—principally
    insects—whereas aquatic organisms are rarely represented. Here, we
    present the first record of true crabs (Brachyura) in amber—from the
    Cretaceous of Myanmar [~100 to 99 million years (Ma)]. The new fossil
    preserves large compound eyes, delicate mouthparts, and even gills.
    This modern-looking crab is nested within crown Eubrachyura, or
    “higher” true crabs, which includes the majority of brachyuran species
    living today. The fossil appears to have been trapped in a brackish or
    freshwater setting near a coastal to fluvio-estuarine environment,


    Why would that evidence that the crab was in a nonmarine environment?

    A marine environment is usually saltwater, not brackish or freshwater.
    See also taphonomy in the discussion section of the paper, in
    particular with regard to synclusions.

    bridging the gap between the predicted molecular divergence of
    nonmarine crabs (~130 Ma) and their younger fossil record (latest
    Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable
    calibration point for molecular divergence time estimates for higher
    crown eubrachyurans.

    Open access:
    https://www.science.org/doi/10.1126/sciadv.abj5689

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