An animal from another age resurfaces: 450 million years later, it's back!

© Alejandro Quintanar/Pexels

When a researcher discovers ” the gold of fools “, he is generally disappointed. This nickname is the one that Pyrite is a mineral composed of shiny iron sulfide and a golden yellow color that is often mistaken for real gold. But for Professor Luke Parry's team at Oxford University, This pyrite has proven to be more valuable than gold itself: it has helped preserve a unique specimen named Lomankus edgecombei, an ancient arthropod related to modern spiders and scorpions. The results of their research were published on October 29 in the journal Current Biology.

A Miraculous Preservation

This discovery is exceptional, because ancient arthropods, which are mainly made of soft tissue, usually decompose within a few days of their death. However, the specimen discovered by Parry's team benefited from a unique chemical combination.

The simultaneous presence of organic matter, iron and the absence of oxygen allowed its fossilization in pyrite. The iron atoms were able to replace the atoms in the body, creating a mineralized, and therefore stronger, replica of the soft tissues. The lack of oxygen slowed down or even stopped the bacterial decomposition process, giving the minerals time to properly penetrate the tissues and replace them. Finally, the presence of organic matter, such as complex carbon-based molecules, may have promoted the formation of organometallic compounds, thereby enhancing the preservation of Lomankus edgecombei.

” We are getting a near-complete picture of their anatomy ,” Parry enthuses, emphasizing the rarity of such preservation. Why all the excitement about such an ancient animal? Parry explains: “Fossils like this tell us a lot about what life looked like on Earth hundreds of millions of years ago.”

Reconstruction of the morphology of the discovered specimen of Lomankus edgecombei. © Parry, Luke A. et al. Current Biology, Volume 0, Issue 0

A 450-million-year-old “biological Swiss Army knife”

The Lomankus has a fascinating peculiarity: its frontal appendages, equipped with small pincers and three long flexible flagella, were probably used to explore their surroundings. They suggest that this arthropod had a unique strategy for exploring its environment, different from what can be observed in other species.

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This adaptation, coupled with the absence of eyes, certainly proves that Lomankus lived in the dark depths of the primitive oceans. Indeed, the ocean depths are completely deprived of sunlight. It therefore did not need this organ to detect its food or predators.

These multifunctional appendages perhaps foreshadow the remarkable diversity of current arthropods, a group that today has the largest number of species on Earth. The latter includes more than a million identified species. Some scientists even put forward much higher figures, going up to several million! You have all come across them at least once: butterflies, bees, ladybugs or dragonflies or even eaten them. Shrimps and crabs are also part of this group.

A fossil site that has not revealed all its secrets

The discovery site, located in New York State, is one of the rare deposits in the world where fossilization by pyrite is observed, alongside the German Hunsrück Slate and the Chinese Chengjiang Biota. It is already famous for its trilobites, but the discovery of Lomankus suggests other equally exceptional finds. In addition, this type of deposit often surprises scientists by revealing organisms with strange and unexpected morphologies. “This fossil suggests that many other discoveries await us at this site », says Parry.

These deposits therefore act as real time capsules, capable of preserving specimens in excellent conditions, which allows researchers to have valuable information on paleobiodiversity and past ecosystems. The data obtained from these deposits also make it possible to test the most recent evolutionary theories and to better understand the mechanisms that led to the diversification of life on our planet. A certain Charles Darwin would certainly have been delighted to know of their existence; unfortunately, he would never see the color of it.

• Researchers have discovered a rare arthropod fossil, the Lomankus edgecombei, preserved in pyrite, 450 million years old.
• The specimen has unique appendages and lived in the deep sea without light, suggesting an exploration strategy distinct from current arthropods.
• This fossil deposit in New York, where pyrite allows for exceptional preservation, could still reveal many similar discoveries.

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