For the first time, a trilobite fossil has been found with preserved gut contents, and an analysis of the specimen suggests this ancient animal had a voracious and unfussy appetite.
Trilobites, arthropods that lived from the Early Cambrian to the end of the Permian (around 521–252 million years ago), were some of the earliest animals to live in the sea. Scientists have uncovered tens of thousands of trilobite fossils over the centuries, but this example of the species Bohemolichas incola, from the Ordovician period, is distinct from the others because its gut contents are preserved inside it.
“Most fossil trilobites are not dead whole animals, but rather shed carapaces from the moulting process, like modern crabs,” says Per Ahlberg at Uppsala University in Sweden. As a result, none of their internal organs are present in the fossil. But this 465-million-year-old trilobite, unearthed in the Czech Republic, was buried alive with a full gut in an undersea mudslide.
To find out what was inside the 465-million-year-old trilobite, Ahlberg and colleagues examined the fossil using high-resolution X-rays, which they used to create three-dimensional digital reconstructions. They found that the arthropod ate a variety of living and dead marine organisms.
The scans revealed crushed shells from ancient crustaceans, echinoderms and bivalves – the early relatives of crabs, sea stars and mussels. Shell fragments in the animal’s gut suggest it was able to crunch through fragile shells or swallow animals whole, and probably made meal choices primarily on the basis of its prey’s size and shell strength.
Judging by signs of digestion, “it seems to have been eating very quickly, stuffing itself almost to bursting”, says Ahlberg. He suspects the trilobite was over-eating to trigger moulting, a strategy shared by some modern arthropods.