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

Trilobites dating back 508 million years have been found preserved in volcanic material, revealing unprecedented detail in 3D. They fossilized so quickly that tiny shells were preserved in place, and soft tissue including mouthparts and internal organs can still be seen.

The trilobites were buried in volcanic flow, the hot, dense material that erupts from volcanoes and sometimes reaches speeds of up to 200 m (656 ft) 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 was deadly hot, and could have burned animals at shallow depths,” says the study co-author. Dr. Greg Edgecombe “The ash must have mixed with seawater as it was being picked up and carried by the tripods that lived on the sea floor,” an archaeologist at London’s Natural History Museum told IFLScience. “This mixing through a column of seawater must have cooled the ash sufficiently.”

These ancient wonders were collected in the Atlas of Morocco, and were given the name “Pompeii” trilobites due to their exquisite preservation in ash. They’re incredibly old, but they’re not the oldest trilobites ever found.

At about 508 million years old, they are younger than the oldest trilobites, which date back to about 521 million years ago. There are also older burrow-shaped trace fossils, called Rusophycus, which are believed to be the work of trilobites and are over 528 million years old.

However, the grouper fish is still remarkable in the degree of preservation it shows.

“What makes our specimens unique, especially pristine, is the preservation of their three-dimensional appendages,” Edgecombe continued. “The appendages are not flattened, reoriented or broken. They are preserved in the orientations of near-life. And because they are preserved as empty space in the rock matrix, we can image them in tomography to see them in three dimensions.”

“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 is published in the journal Sciences.