HMN 2026: How Compound in 500-million-year-old fossils sheds new light on Earth’s carbon cycle

A UT San Antonio-led international research team has identified chitin, the primary organic component of modern crab shells and insect exoskeletons, in trilobite fossils more than 500 million years old, marking the first confirmed detection of the molecule in this extinct group.

The study, led by Elizabeth Bailey, assistant professor of Earth and planetary sciences at UT San Antonio, is published in the journal Palaios. The findings offer new insight into fossil preservation and Earth’s long-term carbon cycle.

Chitin is one of the most abundant organic polymers produced by life on Earth, second only to cellulose. Until recently, scientists believed it degraded relatively quickly after an organism’s death.

This new research adds to a growing body of evidence suggesting that certain biological polymers can persist in the geologic record for far longer than previously assumed.

“This study adds to growing evidence that chitin survives far longer in the geologic record than originally realized,” Bailey said. “Beyond paleontology, this has significant implications for understanding how organic carbon is stored in Earth’s crust over geologic time.”

Bailey brought a geochemical and planetary science perspective to the project, contributing her expertise in stratigraphy, field geology, and the interpretation of how biological materials interact with Earth’s carbon cycle over billions of years.

“I was motivated to pursue this work from my perspective as a planetary scientist interested in how organic molecules play a role in planetary geochemical processes,” said Bailey.

“My collaborators specialize in modern chitin analytics, and they were excited to apply increasingly sensitive techniques to such an ancient and iconic fossil group.”

How carbon is stored

Though this study focused on a small number of fossils, the implications reach well beyond trilobites. Understanding how organic carbon can persist in common geological settings will help scientists reconstruct Earth’s carbon cycle and may inform how carbon is stored naturally within the planet’s crust.

The research also has potential relevance for modern climate discussions. For instance, limestones, which are formed from accumulated biological remains and widely used as building materials throughout human history, often contain chitin-bearing organisms.

“When people think about carbon sequestration, they tend to think about trees,” Bailey said. “But after cellulose, chitin is considered Earth’s second most abundant naturally occurring polymer. Evidence that chitin can survive for hundreds of millions of years shows that limestones are part of long-term carbon sequestration and relevant to understanding Earth’s carbon dioxide levels.”

Early Earth lab

The research began prior to Bailey’s appointment at UT San Antonio, during her postdoctoral fellowship at the University of California, Santa Cruz. While no other UT San Antonio faculty or students were directly involved in this specific study, Bailey anticipates that the findings will create new opportunities within the university’s Early Earth Lab for future student-driven research into the long-term survival of organic molecules in geological materials.

The content is provided for information purposes only.