Sign up for CNN’s Wonder Theory science newsletter. Explore space with news of fascinating discoveries, scientific advancements and more.
CNN
—
A volcanic eruption near what is now a shallow sea in Morocco about 500 million years ago preserved some of the most complete specimens ever discovered of worm-like sea creatures called trilobites, revealing anatomical details never before seen by scientists.
Within seconds, a torrent of hot ash and volcanic gases called a pyroclastic flow engulfed the trilobite, which then cooled and solidified into rock. The animal died on the spot, much like the people who were similarly buried in ash at Pompeii after the eruption of Mount Vesuvius in 79 AD.
For 515 million years, all of this evidence of trilobites lay buried and hidden in a place called the Taterut Formation in the High Atlas Mountains. But an international team of researchers recently used high-resolution X-ray microtomography to peer into the trilobite tomb layers. Their analysis revealed a nearly perfect 3D imprint of the animal’s vaporized corpse in a block of volcanic rock, the scientists reported June 27 in the journal Nature. Science.
Scientists reconstructed 3D digital models from scans of these prehistoric casts, displaying trilobite anatomy in unprecedented detail. The hot volcanic lava that buried the trilobites preserved traces of soft tissue that normally doesn’t fossilize, such as the digestive system, antennae, feeding organs, masses of sensory hairs, and tiny spines on the trilobite’s appendages.
“It’s really amazing that we can recreate this in 3D without any alteration or distortion,” says the lead author. Dr. Abderrazak El Albani He told CNN that the detailed preservation shows that trilobites were anatomically sophisticated animals with many specialized adaptations for feeding and moving on the sea floor.
Chemical analysis of oxygen levels inside the specimen and in the surrounding sediments revealed that the trilobite’s internal organs were filled with ash, which was likely ingested when it suffocated to death by volcanic ash in the seawater, the study authors wrote.
Arnaud Masurier/Poitiers Institute of Environmental and Materials Chemistry/University of Poitiers
Side view of the trilobite Prothorenus, with the digestive system in blue, the mouth structure (hypostomy) in green (far left), and the labium (the bulbous structure above the mouth that in insects is sometimes called the upper lip) in red.
Sedimentary pressure would usually flatten the delicate fossils, but after the eruption buried the trilobites, cold seawater mixed with the hot ash, causing the pyroclastic flow to harden quickly into a solid rock tomb, preserving the trilobite’s mold and preserving its near-perfect shape, says El Albani, a geology professor at the University of Poitiers in France.
El Albani added that the discovery also highlights the urgency of protecting fossil-rich sites in Africa like the Tatert Formation. Unlike the Tatert Formation, Canada’s important Cambrian fossil site, the Burgess Shale, is a UNESCO World Heritage Site. Such protection helps ensure buried remains from Earth’s distant past remain accessible for future research, El Albani said.
Over the past 200 years, paleontologists have identified more than 22,000 species of trilobites from locations around the world that were once covered by oceans. Trilobites are arthropods, similar to modern insects, spiders, millipedes and crustaceans, and evolved into many different shapes and sizes before becoming extinct about 252 million years ago. Most trilobite species were less than 1 inch (2.5 centimeters) long, but some, such as Hungoides bohemicus, were more than 12 inches (30.5 centimeters) long.
Arnaud Masurier/Poitiers Institute of Environmental and Materials Chemistry/University of Poitiers
Microtomographic reconstruction reveals a new species of trilobite, Gigoutella mauretanica, from the Taterut Formation of the High Atlas Mountains.
Trilobites generally had tough exoskeletons that made them easy to fossilize, but the preservation of the soft tissues of this new trilobite is highly unusual, the researchers said. Dr. Melanie HopkinsCurator of Invertebrate Paleontology at the American Museum of Natural History in New York City.
“There are very few trilobite species that are well-preserved enough to see the appendages,” says Hopkins, who studies trilobites but was not involved in the new study. “The level of detail preserved in the Tatert specimen is quite unusual, and it contains some features that have never been observed before,” she said. These features are crucial for understanding how new traits and species evolved, and for tracing relationships between arthropod groups, Hopkins added.
“The more anatomical detail we have, the more precise inferences we can make about how fossil arthropods related to one another.”
The scientists found four trilobite specimens and identified two species new to science, Gigoutella mauretanica and Protolenus (Hupeolenus), the latter an as yet unnamed species within a known genus and subgenus. The specimens ranged in length from about 0.4 inches (11 mm) to 1 inch (26 mm).
“This is the first time the lips have been preserved,” El Albani said. The lips are the bulbous structure above the mouth, sometimes called the upper lip in insects. The cleft behind the lips was also very well preserved. Surrounding it were thin, curved appendages that were probably used for feeding, which also had not been found before in trilobite fossils, the study authors said.
The discovery of these structures raises new questions about the diversity of trilobite feeding appendages and how that affected the diets and habitats of trilobites, as well as the vulnerability of trilobites to changing environmental conditions if they had a highly specialized diet, Hopkins said.
The suddenness of Cambrian volcanic eruptions even left evidence of neighboring organisms that shared the trilobites’ marine habitat. The team found that one G. mauretanica still had a tiny, shelled animal called a brachiopod, about 0.04 inch (1 millimeter) long, attached to its face. This example of commensalism (the coexistence of different types of animals) is extremely rare in the trilobite fossil record, El Albani says.
“This is a unique window into the life history of this specimen from 515 million years ago,” he said. “We hope that other discoveries by our team and other teams in Morocco will lead to the discovery of more or different specimens, providing opportunities to learn more about its life history and evolution.”
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazine.