Volcanic ash preserves rare trilobite fossils with soft tissues intact
Researchers have made an extraordinary discovery, allowing them to learn about the past and acquire previously inaccessible knowledge. This breakthrough would not have been possible without a coincidence and a prehistoric volcanic eruption.
9:29 AM EDT, June 28, 2024
A volcanic eruption occurred during the Cambrian period. The pyroclastic flow and ash flowed into a shallow marine environment, home to ancient arthropods called trilobites. The ash ensured their preservation and soft tissues, which usually degrade or get destroyed during other fossilization processes.
Now, hundreds of millions of years later, researchers have had the chance to study an unprecedented record of these trilobites' three-dimensional anatomy and the smaller creatures that clung to their bodies at that time.
Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system, according to members of the team led by sedimentologist Abderrazzak El Albani from the University of Poitiers in France, as quoted by the portal sciencealert.com.
Researchers say this discovery suggests that volcanic ash deposits in marine environments could be a source of exceptionally well-preserved organisms.
We know that such pyroclastic flows can preserve a snapshot of what they bury. The most famous example is Pompeii, where inhabitants were buried and encased in millions of tons of ash, preserving their final moments in harrowing detail.
Such a discovery is rare
Despite over 22,000 known species of trilobites described and documented over 300 million years from the beginning of the Cambrian, the number of fossil specimens with intact internal anatomy is minimal and usually incomplete. Soft tissues cannot survive the temperature and pressure changes that cause fossilization.
In the Tatelt Formation in Morocco, a fossil deposit with many layers spanning centuries has a thick layer containing volcanic ash and debris. In this layer, El Albani and his collaborators found specimens of two species of trilobites.
The features of this ash layer indicate it was deposited during a single sizeable pyroclastic flow, during which hot ash and gas traveled across the ground away from the volcanic eruption. Minerals indicated rapid interaction between hot volcanic material and salty seawater.
This had never been observed before
To determine this impact on the fossilization process of the trilobite specimens, researchers used micro-CT X-ray imaging to reconstruct the animals' internal anatomy in three dimensions. What they discovered was simply spectacular.
They observed trilobite skeletons that had not been distorted by time. They also examined their antennae, digestive system, and complex anatomy around the mouth. The uniqueness is that some of the discovered elements had never been identified.
The pyroclastic flow even preserved tiny brachiopods — tiny creatures resembling clams, which clung to the shells of trilobites in an epibiotic relationship. These brachiopods were found relaxed, suggesting that both species perished together, either buried alive or shortly after death.
We know a little more about one of the most numerous groups of animals that ever existed on our planet, but the research also revealed an untapped paleontological resource.
