Trilobite Engorged Itself with Food to Capacity

For the first time, a trilobite fossil has been discovered with well-preserved gut contents, providing insights into the eating habits of this iconic ancient creature. Trilobites, which existed from the Early Cambrian to the end of the Permian Period (around 521–252 million years ago), were among the earliest marine creatures. While numerous trilobite fossils have been found over the years, this particular specimen of Bohemolichas incola stands out because its gut contents are still intact.

“Most fossil trilobites are not complete deceased animals, but rather the exoskeletons shed during the molting process, similar to modern-day crabs,” explains Per Ahlberg at Uppsala University in Sweden. As a result, most trilobite fossils do not contain any internal organs. However, the exceptional trilobite fossil, discovered in the Czech Republic, was buried alive in an underwater mudslide with a full gut.

To examine the 465-million-year-old trilobite’s internal contents, Ahlberg and his team used high-resolution X-rays to create three-dimensional digital reconstructions of the fossil. “After that, it was just a matter of comparing the shell fragments in the gut with known fossil organisms to determine the trilobite’s diet,” says Ahlberg.

The scans revealed crushed shells from ancient crustaceans, echinoderms, and bivalves – the early relatives of crabs, sea stars, and mussels. It is believed that the trilobite had a diverse diet, consuming both living and dead marine organisms. The presence of shell fragments in its gut suggests that it was capable of either crushing fragile shells or swallowing its prey whole, and its meal choices were likely influenced by the size and strength of the prey’s shell.

Based on evidence of digestion, Ahlberg notes that the trilobite seems to have been an avid eater, consuming food rapidly and almost to the point of bursting. He speculates that this overeating behavior may have been to induce molting, a strategy observed in some modern arthropods.