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

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

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