Trilobites, those armored, pillbug-like arthropods that teemed across Paleozoic seas, have long captivated fossil hunters. Their hard exoskeletons fossilize reasonably well, and over 20,000 species have been described.
Yet their soft parts—muscles, digestive tracts, guts—rarely survive the ravages of time. Researchers have had to infer diet from mouthparts, the shape of the body, and trace fossils of burrows or feeding marks.
In this case, a specimen of Bohemolichas incola, collected more than a century ago from the Šárka Formation in the Prague Basin, held something remarkable.
When parts of its median axis were peeled away, shell fragments appeared, trapped in what had been its gut cavity. Intrigued, Kraft and his team turned to synchrotron microtomography to scan the fossil noninvasively and reconstruct its internal anatomy in three dimensions.
What emerged was astonishing: a continuous, tightly packed trail of broken shells filling nearly the entire digestive passage from head to tail. The shells belonged to small benthic organisms: ostracods, hyoliths, thin-shelled bivalves, and stylophorans.
An Ancient Glutton In A Good Way
The assemblage suggests B. incola was no picky eater. The fossil’s stomach is stuffed—crammed full of shelly bits. According to coauthor Per Ahlberg, it seems to have been eating rapidly and in large quantities.
The researchers interpret this as evidence of an opportunistic scavenger—one that scooped up whatever small shells it found: dead or weak organisms, fragments, soft prey, or even whole shelled creatures small enough to crush or swallow. In their words, B. incola was a “light crusher and chance feeder.”
One tantalizing additional clue: a crack along the top of the trilobite’s exoskeleton suggests it may have been in the process of molting when it expired.
Many arthropods inflate or bulk up just before shedding their old shell, sometimes ingesting extra fluid or food to help crack open the exoskeleton. The researchers speculate that the feeding frenzy captured in this fossil might be tied to that molting process.
A Digestive System That Echoes 465 Million Years Later
Perhaps the most profound insight from this fossil lies not in what it ate, but how it digested it. The shell fragments appear remarkably undissolved—even their sharp edges are intact. That suggests the gut environment was neutral or alkaline, not strongly acidic.
Why is this important? Many modern arthropods—like crabs and horseshoe crabs—also digest with near-neutral pH guts rather than acidic ones. The observation hints that this might be an ancestral trait in the arthropod lineage, conserved for hundreds of millions of years. In essence, a kind of internal chemistry continuity ties B. incola to modern-day crabs.
The researchers also found traces of scavengers that dug into the soft tissues of the dead trilobite, but they avoided the gut. That avoidance suggests the digestive tract remained noxious—possibly enzymatically active—for some time after death.
This revelation of gut chemistry and its evolutionary implications is arguably the most surprising and powerful: it ties physiology across deep time, and anchors a trait of modern arthropods in a fossil more than 400 million years old.
Putting The Fossil In Context
This is not the first time paleontologists have glimpsed parts of trilobite guts. Earlier discoveries from the Guanshan biota in China, dating back over 500 million years, revealed some trilobites with stomach-like expansions and digestive glands. Those findings challenged earlier assumptions about the evolution of digestive systems in trilobites.
But none of those earlier finds included the actual contents of the gut. The B. incola specimen is the first whose full diet is imaged and catalogued. The Nature paper calls it “the first example of actually being able to see what they were eating.”
In 2024, additional discoveries have continued to enrich our understanding. For example, researchers described remarkably well-preserved trilobites in volcanic ash deposits in Morocco—so-called “Pompeii trilobites”—whose soft anatomy, legs, digestive tracts, and even fine spines are preserved in three dimensions.
These finds collectively show that, under rare and favorable conditions, fossils can carry signals far beyond bones. They can preserve biochemistry, internal organs, even the last moments of life.
A Story That Connects Past, Present, And Hope
I like to imagine the little trilobite B. incola crawling along the Ordovician sea floor. Perhaps it scavenged after storms disturbed sediment, scooping up fragile shells, small carcasses, or weak animals too slow to escape.
Just before its demise, it may have consumed a final meal in haste, perhaps triggered by an internal urge to molt. Then a sudden sediment flow buried it, freezing that moment of gluttony in time.
Centuries passed. The fossil lay in that nodule, overlooked by collectors and curators, until Petr Kraft—remembering it from a childhood visit to the museum—noticed the odd bits perched inside. Only now, with synchrotron imaging and digital reconstruction, has that meal come to light.
What warms the heart is that this discovery blossoms hope for many more such finds. The fossil record is incomplete, but it is not silent. The B. incola specimen shows us that secrets still lie waiting in museum drawers, waiting for new techniques to coax them out.
It suggests that physiology, diet, and chemistry can echo over vast spans of time, connecting extinct creatures to their distant descendants.
In a deeper sense, this fossil is a bridge—a reminder that life is both transient and enduring. The shells in that ancient gut were once alive, serving their own small parts in ecosystems. Now, almost half a billion years later, they speak to us, whispering stories about predation, digestion, survival, and continuity across eons.
May we listen more closely, with curiosity and humility—and may we continue to uncover, piece by piece, the hidden tales locked in stone.
