A recent research by paleontologists from the Faculty of Science at Charles
University in Prague and their colleagues details the preserved intestinal
contents of a 465-million-year-old trilobite. The study was released in
Nature.
Discovered almost a century ago, this exceptional fossil was discovered,
preserved in three dimensions within a structure known as a Rokycany ball.
However, it has only just come to light due to the state-of-the-art imaging
techniques of synchrotron tomography. The study closes a critical knowledge
gap on the ecology of trilobites and their place in Paleozoic
ecosystems.
Since its discovery in 1908 by private collector Karel Holub, the
fossilized trilobite has been kept in the Rokycany museum (now the Museum of
B. Horák, a division of the Museum of West Bohemia in Pilsen). According to
Petr Kraft, the study's first author from the CU Faculty of Science, "I
remember this specimen from my childhood; it was my grandfather's favorite
fossil." For this reason, its picture used to hang in the paleontology
office of the Rokycany Museum, where he volunteered."
Paleontologists did not, however, recognize until the early 21st century,
that the visible fragments of shell in the trilobite's peeled-off median
axis may represent preserved contents of its digestive system. It was not
feasible to inspect them at the time without damaging the unique
fossil.
The scientists made significant progress when they employed synchrotron
tomography, a potent instrument that allowed them to non-destructively and
highly-resolutionly photograph every shell piece in the stomach. One of the
earliest fossils from the Czech Republic to be studied at the European
Synchrotron (ESRF) in Grenoble, France, was the Rokycany trilobite.
"Getting slice images—which are akin to what most people are familiar with
from CT scans at hospitals—is only the first step. After that, each
structure is manually segmented using reconstruction software. After the
fossil's three-dimensional model has been rendered in a virtual photo
studio, the image depth is increased and an incredibly informative figure is
produced, according to Valéria Vaškaninová from the CU's Faculty of Science.
Vaškaninová used this laborious but efficient combination of imaging
techniques for the first time in a 2020 Science paper on the origin of
vertebrate teeth.
The trilobite Bohemolichas incola's digestive system was densely populated
with fragments of calcareous shells from marine invertebrates, including
echinoderms, bivalves, and ostracods, some of which could be identified down
to the species level. It is suggested by the authors that the trilobite was
a light crusher, an opportunistic scavenger, and a chance feeder that
consumed both live and dead animals that either fell apart easily or were
tiny enough to be eaten whole without making an effort to reject the hard
shells.
It is amazing that throughout the digestive tract, the calcareous shells
with thin walls remain partly dissolved. This suggests that an acidic
environment was not encountered by them. Horseshoe crabs and other
contemporary crustaceans have gut environments that are nearly neutral or
slightly alkaline, indicating that this may be an evolutionary trait of
arthropods.
This scavenger became scavenged after death. In the murky sea floor, the
researchers found many footprints of small scavengers that had sunk into the
trilobite's corpse, which was buried at a shallow depth.
It is surprising that they bypassed the intestines and instead seemed to
target soft tissue. The scavengers could have recognized that the digestive
tract's inside was toxic and that some of its digestion enzymes were still
active. However, they were also unlucky because, as escape trails were
missing, a solid "ball" that was quickly developing around the deceased
trilobite confined them.
Provided by
Charles University
