A fascinating “marine Pompeii” discovered in Morocco reveals the anatomy of arthropods frozen in volcanic ash

While everyone goes about their usual business, in a few moments, life stops. Preserved in its state at time T, for eternity or almost.

We are not in Pompeii, Italy, but in Aït Youb, halfway between Marrakech and Agadir, Morocco. And the beings frozen in the volcanic ash are not humans from 79 BC, but trilobites – marine arthropods.

This discovery of exceptional fossils, representatives of a 515 million year old ecosystem, made the front page of the prestigious journal Science (June 27, 2024). We owe it to a Franco-British research team led by researchers from the University of Poitiers.

Hairs, thorns, digestive tract…

Using an imaging technique (X-ray microtomography), scientists have revealed incredible anatomical details in these petrified invertebrates which, despite the millions of specimens already collected elsewhere in the world, had until now been overlooked. unnoticed. And for good reason: the trilobites of Aït Youb are the best preserved ever discovered!

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This astonishing preservation can be explained: During the volcanic eruption, living organisms 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.”we detail in a press release (University of Poitiers / CNRS).

Now, these molds “preserve fine details of the trilobites’ outer surface, including hairs and spines along the appendages. Their digestive tract was also preserved after filling with ash.” The same goes for “brachiopods”, small shells attached to their external skeleton by a fragile peduncle.

A major scientific breakthrough

Greg Edgecombe, a curator at the Natural History Museum in London, arthropod specialist and co-author of the study, does not hide his emotion:

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I’ve been studying trilobites for almost 40 years, but I’ve never felt like I was looking at living animals like I did with thesehe confides (press release).

In the animal family tree, arthropods correspond to the branch that includes insects, crustaceans, spiders and even modern millipedes. Among them, trilobites disappeared 250 million years ago, during the mass extinction that occurred at the end of the Permian. The question that has been plaguing specialists until now is: how exactly did they feed?

The new study reveals the presence of a “grouping of pairs of specialized legs around the mouth”never observed with such a level of detail. But above all, for the very first time, it reveals the presence of a labrum, “a fleshy lobe that acts as an upper lip in modern arthropods.”

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Exploration of volcanic underwater environments

“This discovery demonstrates the essential role of volcanic ash deposits for the preservation of fossils and the crucial importance of exploring underwater volcanic environments”underlines Professor Abderrazak El Albani, teacher-researcher at the Institute of Chemistry of Media and Materials in Poitiers, who directed the work (press release).

The imaging technique implemented also constitutes “a powerful tool for observing fossilized objects in very hard rocks in 3D, without risk of altering them. Thus, pyroclastic deposits should become new study targets given their exceptional potential to trap and preserve biological remains, even soft ones, without generating degradation”advance-t-il.

And to conclude: New windows should thus open onto the past of our planet.