Trilobites preserved in incredible detail from eruptions like Pompeii

A fossil dig site in Morocco has been dubbed the “Pompeii of Trilobites” because it contains highly detailed fossil molds of trilobites that were preserved after pyroclastic flows from a volcanic eruption some 509 million years ago.

“My jaw dropped to the table.” John Patterson “We have never seen these fossil trilobites preserved in such detail before and they are without a doubt the best-preserved trilobites ever found,” said researcher David Schneider of the University of New England in Armidale, Australia.

Trilobites are marine arthropods that lived from about 520 to 252 million years ago. Over 22,000 species are known, and countless fossils have been found, but usually only their tough exoskeletons. Soft parts of the organisms are rarely found, and they are always flattened and damaged.

But as soon as Patterson saw scans and images of the trilobite fossil, collected southwest of Marrakech, Morocco, in 2022, he knew it was something special.

“In one of the more complete specimens, all of the appendages are preserved in 3D, right down to the setae on the walking legs,” he says.

So far, Patterson and his colleagues have collected four specimens of two different species of trilobites, each measuring about one centimeter, from the Tatert Formation in Morocco. Two of the four trilobite specimens are: ProtrenusBut the researchers are not sure if it belongs to a new species. Zygothera mauretanica.

Pompeii is prized by archaeologists because volcanic ash from Mount Vesuvius fell rapidly on the Roman city, preserving its structures and inhabitants. As the ash cooled into rock, each body decomposed, leaving behind cavities that formed perfect molds. The same thing happened with the trilobites, Patterson says.

The team scanned the molds with a microCT scanner, which allowed them to create a complete 3-D image of the organisms. “With these specimens, we can see anything from any angle,” Patterson says.

The scans allowed the team to resolve key details of the trilobite’s anatomy that have long been debated, such as the structure of its feeding organs: one individual’s digestive tract was filled with volcanic material, and thus apparently preserved, suggesting it must have swallowed ash when it died.

Another insight is how the creature used its legs: “They have these very rough spikes on the inside of their legs,” Patterson says, “which would have acted as tools to chop up prey into small pieces. In other words, they were biting with their legs and pushing food up through their legs into their mouth.”