508-million-year-old trilobite fossils from Pompeii show features never seen before

Trilobites dating back 508 million years have been found preserved in volcanic material, revealing never-before-seen detail in 3D. Their fossilization was so rapid that tiny shells were preserved in place, and soft tissue including mouthparts and internal organs can still be seen.

The trilobites were buried in lava flows, the hot, dense material that erupts from volcanoes and sometimes reaches speeds as high as 200 meters (656 feet) per second. It usually burns any living organisms in its path, but this may change in the marine environment.

“The sea surface onto which the ash flowed would have been deadly hot, and would have burned animals at shallow depths,” says the study co-author. Dr. Greg Edgecombe From the Natural History Museum, London, to IFLScience. “The ash likely mixed with seawater during its capture and trapping of trilobites that lived on the sea floor. This mixing in a column of seawater must have cooled the ash sufficiently.”

The ancient wonders, collected in the High Atlas of Morocco, have been dubbed the “Pompeii” trilobites because of their remarkable preservation in the ash. They are incredibly old, but they are not the oldest trilobites ever found.

It is about 508 million years old, making it younger than the oldest trilobites, which date back to about 521 million years ago. There is also an even older burrow-shaped trace fossil, called Rusophycus, which is thought to have been the work of trilobites and is over 528 million years old.

However, the whip snapper is still remarkable for the degree of preservation it exhibits.

“What makes our specimens unique, especially pristine ones, is the three-dimensional preservation of their appendages,” Edgecombe added. “The appendages have not been flattened, reoriented or broken. They have been preserved in orientations close to life. And because they are preserved in a vacuum in the rock matrix, “We can CT scan it to see it in 3D.”

“The appendages preserved in shale can preserve their hairs beautifully, but the fossils are so compact that they are almost two-dimensional, and we have to use destructive sampling to mechanically coring off the tops of the appendages in order to see the bottoms. Our specimens are as perfect after study as they were before.”

These never-before-seen details mean we now see trilobites closer to life than we’ve ever seen them before, complete with a slit-like mouth and unique vertical feeding appendages. Isn’t that beautiful?

The study was published in the journal Sciences.