Artist’s impression of the volcanic explosion that buried the trilobites. Credit: Abderrazak El Albani
A team of researchers from the University of Poitiers, led by Professor Abderrazak El Albani, has just published in the leading American journal Sciencean article reporting the discovery in Morocco of two new species of trilobites in an exceptional state of conservation.
According to a press release from the scientific team whose work was coordinated by Professor El Albani, a lecturer and researcher at the Institute of Chemistry of Environments and Materials in Poitiers, these fossil arthropods found petrified in their last posture are representatives of an ecosystem 515 million years old. They were discovered in levels of volcanic ash in Aït Youb, a marine “Pompeii” in the Souss-Massa region.
For Professor El Albani, “This discovery demonstrates for the first time the essential role of underwater volcanic ash deposits for the preservation of fossils and the crucial importance of exploring volcanic underwater environments.”
It also demonstrates that “The non-destructive imaging technique, high-resolution X-ray micro-tomography (XRµCT), is a powerful tool for observing fossilized objects in very hard rocks in 3D, without the risk of altering them, because by digitally filling the voids left by the organisms, they were able to create casts of the extinct bodies with a striking level of detail.”
Thanks to this discovery, he added, “pyroclastic deposits should become new targets for study given their exceptional potential to trap and preserve biological remains, even soft ones, without generating degradation generally leading to the incompleteness of specimens or even their destruction. New windows are thus opening onto the past of our planet.”
Explaining this discovery, the team of researchers specifies that volcanoes located at the boundaries of tectonic plates are known for their explosive and large-scale eruptions, which can generate several tens of km3 of material. These eruptions can trap present life almost instantly, thus preserving under their ashes the evidence of entire civilizations, such as those of Santorini and Vesuvius.
They claim that with more than 22,000 species discovered spanning the Paleozoic era (539 to 252 Ma), trilobites are arguably the best-known fossil invertebrates. While their calcite exoskeleton gives them a high potential for fossilization, the reason for their abundance in the fossil record, their non-mineralized appendages and internal organs are only known through a limited number of specimens.
In Aït Youb, details the same source, “515 million years ago, during a volcanic eruption, the living organisms present were buried by fiery clouds. The biological tissues were then consumed by the intense heat, leaving only cavities in the solidified ash: the molds of the organisms.”
This study, adds the press release, provides new insight into the anatomical organization of trilobites, particularly the cephalic part. In particular, it reveals for the first time in this class of fossil arthropods the presence of a labrum, a soft mouthpart that acts as an upper lip in current euarthropods, thus closing a debate that is more than a century old.
Given the global importance of the site studied, it would be essential and crucial to protect it by classifying it as a UNESCO world heritage site, the press release added.
