Chitin is the primary organic component of modern crab shells and insect exoskeletons and is considered Earths second most abundant naturally occurring polymer after cellulose. Until recently, prevailing thought held that chitin readily broke down after an organism died, leaving little chance of survival in ancient fossils. The new work adds to growing evidence that this durable biopolymer can survive hundreds of millions of years under the right conditions.
The research was led by Elizabeth Bailey, an assistant professor of earth and planetary sciences at UT San Antonio, who brought a geochemical and planetary science perspective to the project. Bailey contributed expertise in stratigraphy, field geology and the interaction between biological materials and the long term carbon cycle. She collaborated with specialists in modern chitin analytics who applied increasingly sensitive laboratory techniques to investigate the chemistry of the trilobite remains.
Bailey and her colleagues focused on Cambrian trilobites from the Carrara Formation in western North America, a well known fossil bearing sequence that records early Paleozoic marine environments. Using advanced analytical tools, the team detected chemical signatures consistent with surviving chitin within the fossilized exoskeletons. Their results demonstrate that original organic components can be retained in these iconic fossils, rather than being entirely replaced by minerals.
The findings have broad implications beyond paleontology because they illuminate how organic carbon can be stored in common sedimentary settings. Chitin containing organisms contribute organic matter to marine sediments that may eventually lithify into carbonate rocks such as limestone. Evidence that chitin can survive deep time indicates that these rocks form part of a long term carbon sequestration system within Earths crust.
The study also links fossil preservation to modern climate discussions by highlighting the role of limestones and other biogenic rocks in regulating atmospheric carbon dioxide. Many limestones, widely used as building materials, originate from accumulated shells and skeletons that included chitin bearing organisms. If significant fractions of that chitin persist, these rocks represent a stable reservoir of organic carbon operating over hundreds of millions of years.
Bailey emphasized that thinking about carbon sequestration only in terms of forests and surface ecosystems overlooks these ancient geological stores. She noted that chitin, as Earths second most abundant natural polymer, plays a substantial role in the long term burial and retention of carbon. The new results suggest that standard models of the carbon cycle may need to account more explicitly for the durability of such polymers in the subsurface.
The project began during Baileys postdoctoral fellowship at the University of California, Santa Cruz, supported by the Heising Simons Foundations 51 Pegasi b Fellowship in Planetary Astronomy. At that time she expanded from theoretical planetary science work into laboratory based studies of planetary and geological materials. This transition positioned her to bridge paleontology, geochemistry and planetary science in the current study.
Bailey now leads the Early Earth Lab at UT San Antonio, where her group builds computer models and conducts chemical analyses of meteorites and ancient terrestrial rocks to investigate how the Solar System, including Earth, formed and evolved. Although no other UT San Antonio faculty or students were directly involved in this particular project, she expects the trilobite chitin discovery to open new avenues for student driven research on the long term survival of organic molecules in geological materials.
The team reported its findings in the journal PALAIOS in an article titled Evidence for surviving chitin in Cambrian trilobites from the Carrara Formation, Western North America. The work underscores how targeted geochemical techniques can reveal original organic compounds in fossils once thought to be purely mineral. As analytical methods continue to improve, similar approaches may uncover additional examples of ancient biopolymers preserved in the rock record.
Research Report:Evidence for surviving chitin in Cambrian trilobites from the Carrara Formation, Western North America
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