CARNIVOROUS TRILOBITES: MORPHOLOGIC, ICHNOLOGIC, AND TAPHONOMIC EVIDENCE

Mounting evidence from polymerid trilobites and their trace fossils suggests that many, and perhaps the majority, of taxa were active predators or scavengers. Morphologic evidence from the exoskeleton includes attachment mechanisms allowing active movement of the hypostome, and in some, hypostome morphology (e.g., forked serrated blades capable of slicing prey). Spiny appendages may have assisted in restraining prey.

Numerous Rusophycus-Planolites trace fossil associations representing the interactions of trilobites and ‘worms’ provide clear documentation of trilobite attack strategy and prey manipulation. A large variety of Rusophycus predation traces are now known. The trilobites’ incursions into the sediment for purposes of feeding are remarkably precise, suggesting that chemosensory skills may have played a large role in locating prey that was concealed within sediment.

Fossilized alimentary tracts, preserved through early diagenetic mineralization, provide another source of information about trilobite ‘paleogastronomy,’ the dietary habits of trilobites. Numerous trilobites are now known to preserve digestive tracts, and nearly all have mineralized (not sediment-filled or sclerite-filled) guts. This implies that the guts were fluid-filled at the time of death and burial, a condition common in extant carnivorous arachnomorph arthropods.