508-million-year-old “Bompeii” trilobite fossils show never-before-seen features

Trilobites dating back 508 million years are preserved in volcanic material, revealing never-before-seen detail in 3D. Their fossilization was so rapid that small shells are preserved in situ, and soft tissues, including mouthparts and internal organs, are still visible.

The trilobites were buried in a pyroclastic flow, a hot, dense material that sometimes reaches high velocities when ejected from volcanoes. 200 meters (656 feet) per second. Normally, it burns up any life in its path, but that can change in the ocean system.

“The surface of the ash-flowing ocean would have been dangerously hot and, yes, would have burned animals at shallower depths,” study co-author Dr. Greg Edgecombe The Natural History Museum in London told IFLScience. “As the trilobites that live on the ocean floor are carried and added, the ash is mixed with seawater. This mixing through a column of seawater must have cooled the ash sufficiently.

Collected in Morocco’s High Atlas, the ancient wonders were nicknamed the “Bombi” trilobites because of their remarkable preservation in ash. They are incredibly old, but they are not the oldest trilobites ever discovered.

About 508 million years old, they are younger than the oldest trilobites, which are about 521 million years old. There are also older trace fossils in the form of burrows called Rusophicus, which are thought to be the work of trilobites and are thought to be more than 528 million years old.

However, comparative whipper snappers are still notable for the level of protection they exhibit.

“What makes our specimens unique, and indeed particularly primitive, is the three-dimensional preservation of their appendages,” Edgecombe continued. “The joints are not flattened or rearranged or broken. They are preserved close to life orientations. And because they are preserved in voids in the rock matrix, they can be imaged tomographically to see them in 3D.”

“Appendages preserved in shale can preserve their composition beautifully, but the fossils are compressed to the point where they are almost 2D, and we have to use destructive sampling to mechanically excavate the upper parts of an appendage to see the lower parts. Our models are as perfect after examination as they were before.

This never-before-seen detail gives us a closer look at trilobites than we’ve seen before, with slit-like mouths and distinctive cephalic feeding appendages. Isn’t she beautiful?

The study is published in the journal Science.

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