Astonishing Discovery: Uncovering of 500-million-year-old ‘Pompeii’ Trilobite Fossils Resets the Scientific Understanding of this Extinct Group

Researchers have discovered exquisitely preserved “Pompeii” trilobite fossils in Morocco. Advanced imaging techniques revealed more details about these ancient creatures with the new anatomy and preservation that they had.

Researchers have described some of the most exquisite three-dimensional trilobite fossils yet found. More than 500 million years old, the fossils were collected in the High Atlas of Morocco and have been called the “Pompeii” trilobites by scientists.

Artistic reconstruction of two species of trilobite an instant before burial in a flow of volcanic ash 510 million years ago. Credit: Prof. A. El Albani, Univ. Poitiers

A team of international scientists, led by Prof Abderrazak El Albani—a geologist based at the University of Poitiers and originally from Morocco—has conducted studies on Cambrian-period trilobites. The researchers also included Dr. Greg Edgecombe, a paleontologist at the Natural History Museum.

Microtomographic reconstruction of the head and anterior trunk (“body”) limbs of the trilobite Protolenus (Hupeolenus) in ventral view. Credit: Arnaud Mazurier, IC2MP, Univ. Poitiers

Dr. Greg Edgecombe writes: “I’ve worked on trilobites for almost 40 years, but I don’t think I’ve ever had a sensation of staring at living animals as much as I have with these guys. I’ve seen plenty of soft anatomy of trilobites, but it’s the 3D preservation here that is really out of this world. Who would have thought that volcanic ash in shallow marine environments would turn out to be such stuff that exceptional fossil preservation dreams are made of?”

Microtomographic Reconstruction of the Head and Anterior Trunk Limbs of the Trilobite Protolenus
Microtomographic reconstruction of the head and anterior trunk (“body”) limbs of the trilobite Protolenus (Hupeolenus) in ventral view. Credit: Arnaud Mazurier, IC2MP, Univ. Poitiers

Because of their hard, often rather well-preserved calcified exoskeleton, remains in the fossil record make trilobites among the best-known fossil marine animals. More than 20 000 species have been described during the last two centuries by paleontologists.

However, despite this phenomenal diversity, a full scientific understanding of the group as a whole has until now been hindered by the relative rarity of soft tissue preservation. Because the Moroccan trilobites were buried in hot ash in seawater, their bodies began to fossilize rapidly as the ash cemented to rock – much like what happened to the people of Pompeii when Mount Vesuvius erupted.

The ash molds preserved each segment of their bodies, their legs, and even the hair-like structures that ran along the appendages. The trilobites’ digestive tract was also preserved after it filled with ash. Even small “lamp shells” attached to the trilobites’ exoskeleton remained attached by fleshy stalks as they were in life.

https://youtu.be/twnAvC3IARk

Supplementary video. Credit: Greg Edgecombe

New Discoveries and Methods
Co-author and lead author Prof Abderrazak El Albani said: “As a scientist working previously on end-Permanian fossils, but also on other ages and from various parts of the world, I was more than excited to discover such exceptional quality of fossils in a volcanic context. I am convinced that pyroclastic deposits need to be targeted in the near future since, in my opinion, they offer an extraordinary potential for trapping and preserving biological remains of delicate soft tissues.”. These results promise to open a wide window onto the discovery of the evolution of life on Earth, our planet.

Microtomographic Reconstruction of the Trilobite Gigoutella mauretanica in Ventral View
Microtomographic reconstruction of the trilobite Gigoutella mauretanica in ventral view. Credit: Arnaud Mazurier, IC2MP, Univ. Poitiers

Using CT scanning and computer modeling of virtual X-ray slices, researchers have found appendages arranged at the edge of the mouth, which had curved spoon-like bases, but were so small they had gone undetected in less perfectly preserved fossils. Here, as a case in point, one can find it was earlier believed that trilobites had three pairs of head appendages behind their long antennae, while both Moroccan species in this study showed that there were four pairs.

For the first time in trilobites, a labrum was described as a fleshy lobe covering the mouth.

Coauthor Harry Berks of the University of Bristol said, “Results showed—quite exquisitely—the clustering of specialized leg pairs around the mouth area, giving us a much clearer view of trilobite feeding than we ever had before. The limbs displayed an inward-facing battery of dense spines, similar to that of the horseshoe crab today.”.

Trilobites are perhaps one of the more charismatic creatures fossilized in the record of ancient life, and recent discoveries of superbly preserved “Pompeii” trilobites from Morocco have managed to add a whole new dimension to our understanding of these ancient marine arthropods. Such great fossils, dating back more than 500 million years ago in the Cambrian, were found in the High Atlas mountains of Morocco. Nicknamed the “Pompeii” trilobites, these extinct creatures are preserved in volcanic ash exceptionally well and hence have given insights into the anatomy and behavior of these long-lost animals like never before.

Detailed investigations on these fossils were carried out with modern imaging techniques by an international team of scientists led by Prof Abderrazak El Albani of the University of Poitiers. According to Dr. Greg Edgecombe, a paleontologist at the Natural History Museum of London, three-dimensional preservation of fine anatomy resembles seeing live animals; conditions never seen before are exposed. Rapid entombment, like what happened to Pompeii’s citizens when Mount Vesuvius erupted, conserved trilobites in volcanic ash deposited in shallow marine environments.

Trilobites, whose calcified exoskeletons have made them a staple of paleontology, seldom were preserved for soft tissues. Even so, the Moroccan “Pompeii” trilobites, buried in ash that rapidly cemented into rock, have retained impressive details from segmented bodies and legs to delicate appendages. Even the digestive tracts of the trilobites, filled with ash, and the attached “lamp shells” are intact and provide new insights into their ecology and preservational dynamics.

As noted by the professor, these findings open up a whole set of possibilities in which pyroclastic deposits play a very key role in preserving exceptional biological remains. State-of-the-art CT imaging and virtual X-ray modeling were used to enable the identification of new, previously unknown anatomy, including differentiated leg pairs around the mouth and a new labrum—a fleshy lobe that covered the trilobite mouth.

Co-author Harry Berks of the University of Bristol notes that the amazing discovery brought out with this is evidence of feeding mechanisms in trilobites, a bunch of special leg pairs and spines, probably as densely packed as those of modern horseshoe crabs. Not only will these findings bring insight into the biology of trilobites but again emphasize, with an exclamation mark, the importance of pristine preservation for the reconstruction of ancient Earth’s ecosystems and the evolutionary history of life.

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