A fossil site in Morocco has been called the “Pompeii of trilobites” because it contains sublimely detailed fossilised moulds of the creatures, preserved after a pyroclastic ash flow from a volcanic eruption around 509 million years ago, during the Cambrian period.
“They are absolutely, no question, the best-preserved trilobites ever found,” says John Paterson at the University of New England in Armidale, Australia
Trilobites are marine arthropods that existed from about 520 million years ago until nearly 252 million years ago. We know of more than 22,000 species and countless fossils have been discovered, but these are normally just their tough exoskeleton. The creatures’ soft parts are only found on rare occasions, and have been damaged.
However, the trilobite fossils collected in 2022 from south-west of Marrakesh, Morocco, are something special, says Paterson. “On one of the more complete specimens, all of the appendages are preserved in 3D, right down to the bristles on their walking legs,” he says.
This fossil shows the digestive system (blue), the hypostome (green), the labrum (red) and selected appendages (Arnaud Mazurier/University of Poitiers).
So far, Paterson and his colleagues have collected four specimens, each only around a centimetre long, representing two species from the Tatelt formation in Morocco. Two of the four trilobite specimens belong to the genus Protolenus, but the researchers are unsure whether they belong to a new species. The other specimens are Gigoutella mauretanica.
Pompeii is prized by archaeologists because ash from Mount Vesuvius quickly descended on the Roman city, preserving its structures and inhabitants. Once the ash cooled and formed into rock, each of the bodies decomposed, leaving a cavity that represents a perfect mould. The same thing happened to the trilobites, says Paterson.
The team scanned the moulds with a micro CT scanner and was able to create perfect 3D images of the creatures. The scans have allowed the team to resolve some important details of trilobite anatomy that have been long debated, such as the structure of its feeding apparatus. For one of the individuals, it must have swallowed ash as it died because its digestive tract is filled with volcanic material and, hence, clearly preserved.
Another insight was how the creatures used their spiny legs as shredding tools. “They chewed with their legs and pushed the food from their legs up to their mouth,” says Paterson.
This story is based on an article in New Scientist. The original research was published in Science.
Bill Gray