A remarkably well-preserved trilobite fossil, discovered in Morocco, is yielding new insights into the Earth’s carbon cycle and the surprising longevity of organic molecules. Researchers have identified chitin – a primary component of exoskeletons in modern arthropods like crabs and insects – within the 500-million-year-old remains, challenging previous assumptions about the degradation of biological materials over geological timescales.
The discovery, detailed in recent publications, centers around fossils unearthed in the High Atlas mountain range. These trilobites, ancient marine creatures distantly related to modern horseshoe crabs, were rapidly buried in volcanic ash following an eruption, a preservation event researchers have likened to the Roman city of Pompeii – hence the nickname “Pompeii trilobites.” This rapid burial shielded the organisms from scavenging and decay, resulting in exceptional three-dimensional preservation, including soft tissues.
Chitin, a complex sugar polymer, is the second most abundant biopolymer on Earth, after cellulose. Its presence in these ancient fossils is significant because it was previously believed to degrade relatively quickly after an organism’s death. The identification of chitin in the Moroccan trilobites suggests that this resilient molecule can persist for hundreds of millions of years under the right conditions.
“This study adds to growing evidence that chitin survives far longer in the geologic record than originally realized,” said Elizabeth Bailey, assistant professor of earth and planetary sciences at UT San Antonio, who led the research. “Beyond paleontology, this has significant implications for understanding how organic carbon is stored in Earth’s crust over geologic time.”
The research team employed advanced analytical techniques to confirm the presence of chitin within the fossilized remains of the trilobite Olenellus. The ability to detect chitin in such ancient samples opens new avenues for investigating the composition and preservation of other fossilized organisms. Previously, the molecule had not been detected in trilobite fossils despite their abundance in the fossil record.
The implications extend beyond simply understanding fossil preservation. Chitin’s persistence has ramifications for understanding the Earth’s long-term carbon cycle. Limestone, a common sedimentary rock formed from the accumulation of marine organisms, often contains chitinous remains. The discovery suggests that these rocks may represent a significant, and previously underestimated, long-term carbon sink.
“For example, limestones, which are formed from accumulated biological remains and widely used as building materials throughout human history, often contain organisms containing chitin,” notes SciNews. This raises the possibility that even seemingly inert materials like marble could harbor significant reserves of organic carbon.
Trilobites themselves are valuable tools for paleontologists and geologists. With over 20,000 identified species, they provide a comprehensive dataset for analyzing the evolutionary history of extinct species. Their widespread geographic distribution also makes them useful “index fossils” for dating rock layers.
The exceptional preservation of the “Pompeii trilobites” allows for detailed study of their anatomy, including the digestive system and other soft tissues, which are rarely preserved in fossils. Dr. Greg Edgecombe, a paleontologist at the Natural History Museum, described the experience of studying these fossils as feeling like looking at animals that “died yesterday,” a testament to the remarkable level of detail preserved in the volcanic ash.
Chitin, being non-toxic and biodegradable, has found applications in modern medicine, particularly in wound dressings. However, the discovery of its longevity in fossils highlights its potential role in long-term carbon sequestration and the preservation of organic matter within the Earth’s geological record. Further research is expected to focus on identifying other organic molecules within ancient fossils and refining our understanding of the processes that govern their preservation.
The findings underscore the importance of tafonomy – the study of what happens to an organism after death – in understanding the fossil record and the Earth’s biogeochemical cycles. The ability to detect and analyze ancient biomolecules like chitin provides a new window into the past, offering insights into the evolution of life and the planet’s long-term carbon dynamics.
