Until now, the diet of trilobites could only be assessed through circumstantial evidence, but researchers recently discovered the first example of a trilobite preserving traces of its last meal frozen in time.

What is known

The entire trilobite Bohemolichas incola is preserved in fine 3D detail in a siliceous conglomerate shell. Paleontologist Petr Kraft of Charles University in the Czech Republic and his colleagues found tightly packed shell fragments inside the fascinating 465-million-year-old digestive tract.

This scan shows the full shape of the trilobite’s body, with yellow mouthparts and differently colored food particles / Photo: Petr Kraft/Nature

The shells showed no signs of dissolution and their sharp edges remained intact, indicating that the trilobite was neutral rather than acidic throughout the length of its digestive tract, the researchers explained. This is how modern-day crustaceans and spiders, which belong to two different modern groups that claim to be distant relatives of trilobites, digest their food.

The digestive tract was almost completely full, and some parts were still large enough to be identified. All these pieces of trilobite prey belong to benthic invertebrates that lived at the bottom of the sea during the Ordovician period.

• The most common shell fragments were ostracods, small shrimp-like crustaceans whose descendants still live today.
• The trilobite also ate hyaline snails, extinct starfish and sea urchins called stylophores, and other thin-skinned animals that were probably bivalve.

Scanning the contents of the digestive tract is shown above. Stylophore echinoderm is marked below in red, hyalite shells in purple, ostracod fragments in blue / Photo: Petr Kraft/Nature

Considering this type of indiscriminate eating behavior, scientists conclude that: B. incola was most likely an undemanding scavenger, collecting whatever was at the bottom.. The authors call it a “shredder,” which collects dead or live animals that decompose easily or are small enough to be swallowed whole.

The entire digestive tract of the trilobite and some defects in its thorax suggest that the animal may be about to molt. In order for arthropods to grow, they must shed their armored exoskeletons and shed their old ones. The digestive system of such animals often swells before molting to help push out the old shell and make room for the new one.