A collection of fossils unearthed in the High Atlas mountains of central Morocco have been described by researchers as some of the best-preserved trilobites ever found.
The specimens owe their remarkable condition to the hot ash that enveloped them more than 500 million years ago during the Cambrian period.
The 'Pompeii trilobites', as they have become known, provide new information about this large and diverse group of extinct marine animals, which could lead to significant discoveries about the evolution of life on Earth, say the scientists. Their findings were published today in the journal, Science.
Trilobites are some of the best studied fossil marine animals on the planet. Their hard exoskeleton has resulted in an excellent level of representation in the fossil record, with over 20,000 species described in the past two centuries.
But the exoskeleton only tells half the story about this diverse animal group – soft tissue tells the other half. But specimens with well-preserved soft tissue are rarely found, which is why the Moroccan trilobite discovery is so significant.
Encased in hot ash and sea water, the bodies of the marine animals would have fossilised very quickly as the ash turned swiftly to rock, according geologist Professor Abderrazak El Albani, who led the international team of scientists.
The rapid fossilisation is comparable to way inhabitants of Pompeii were preserved following the eruption of Mount Vesuvius, say the scientists.
The ash moulds preserved every single segment of the trilobites' bodies. The hair-like structures that ran along their legs can still be seen, as can the small 'lamp shells', a type of marine invertebrate, which were found attached to their exoskeletons. Incredibly, even the digestive tracts of the animals remain, the ash that filled them leaving them perfectly formed.
“I’ve been studying trilobites for nearly 40 years, but I never felt like I was looking at live animals as much as I have with these ones," says Natural History Museum palaeontologist Dr Greg Edgecombe, who was part of the research team.
"I’ve seen a lot of soft anatomy of trilobites, but it’s the 3D preservation here that is truly astounding."
A fleshy lobe covering the mouth, called a labrum, was also documented for the first time in trilobites.
“As a scientist who has worked on fossils from different ages and locations, discovering fossils in such a remarkable state of preservation within a volcanic setting was a profoundly exhilarating experience for me," says Lead author, Prof Abderrazak El Albani.
Using CT scanning and computer modelling, the team found that the appendages located at the edge of the mouth had curved spoon-like bases, so tiny they had gone unnoticed in less perfectly preserved fossils. Indeed, the analysis revealed that the two Moroccan species in this study showed four pairs of head appendages behind their long antennae, when previously it was thought that trilobites had just three pairs.
“The results revealed in exquisite detail a clustering of specialised leg pairs around the mouth, giving us a clearer picture of how trilobites fed," reveals co-author Harry Berks, from the University of Bristol. "The head and body appendages were found to have an inward-facing battery of dense spines, like those of today’s horseshoe crabs.”
The research team say that the one of the most important (and unexpected) outcomes of the work was the potential "bonanza for exceptional fossil preservation” that could be discovered in areas where volcanic ash and shallow marine settings combined.
“I think pyroclastic deposits should become new targets for study, given their exceptional potential for trapping and preserving biological remains, including delicate soft tissues. These findings are anticipated to lead to significant discoveries about the evolution of life on our planet Earth," concludes Professor Abderrazak El Albani.
The paper, Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites, was published online in the journal, Science.
More remarkable prehistoric discoveries:
- “This place was just crazy rich with dinosaur footprints”. Scientists buzzing after huge prehistoric discovery in Alaska
- Giant prehistoric ichthyosaur found in UK might be largest marine reptile ever, say scientists
- Giant pre-historic worms discovered in Greenland
- Britain's lost beasts: when did the moose, wolf and bear go extinct in UK?
