Soft tissue preserved in trilobite fossil reveal its last meal

A 465-million-year-old trilobite fossil with preserved gut contents has revealed the ancient creature’s final meal.

Trilobites are extinct arthropods (related to spiders, insects and crabs) with hard exoskeletons. They were among the most diverse and populous creatures, living across many epochs of Earth’s geological history from the early Cambrian period (541–484 million years ago) to the end of the Permian (299–251 million years ago).

In that 270-million-year span, more than 20,000 species of trilobite existed and their fossilised remains uncovered by palaeontologists in rocks around the world.

These ancient ocean-dwelling creatures are so common in the fossil record because of their abundance and also because of their propensity to become fossilised. This is due to the environments in which they lived – moist sediments are great at fossilising ancient life – and their hard external skeletons, which are very easily preserved.

But the trilobite fossil described in a paper published in Nature is special because of the soft tissues that have been preserved.

The fossil was discovered in what is now the Czech Republic. The trilobite in question was alive about 465 million years ago during the Ordovician period (488–444 million years ago). It is a specimen of the species Bohemolichas incola.

At this time, central Europe was located in the southern tropics. The ancient Tornquist Sea separated many of the pieces of the puzzle which make up today’s European continent.

It is the first time that the stomach contents of a trilobite have been discovered. Until now, the feeding habits of these creatures has had to be inferred indirectly by analysing their mouths and comparison with living and other extinct organisms.

The creature’s tightly packed gut revealed fragments of shells that belonged to marine creatures including ostracods, hyoliths, bivalves and stylophoran echinoderms.

“The non-selective feeding behaviour of B. incola suggests that it was predominantly an opportunistic scavenger, because predatory arthropods are usually selective in their diet preferences,” the authors write.

Bohemolichas had “light” crushing ability, meaning it could break the weaker shells of smaller animals. It was a chance feeder that ate dead or living animals, which either disintegrated easily or were small enough to be swallowed whole.

The scavenger became the scavenged after death. The authors note: “Scavengers burrowing into the trilobite carcase targeted soft tissues below the glabella but avoided the gut, suggesting noxious conditions and possibly ongoing enzymatic activity.”

Leaving the guts untouched meant that, 465 million years later, we have this trilobite’s last bite.

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