Uniquely preserved gut contents illuminate trilobite palaeophysiology.

Trilobites are among the most iconic of fossils and formed a prominent component of marine ecosystems during most of their 270-million-year-long history from the early Cambrian period to the end Permian period1. More than 20,000 species have been described to date, with presumed lifestyles ranging from infaunal burrowing to a planktonic life in the water column2. Inferred trophic roles range from detritivores to predators, but all are based on indirect evidence such as body and gut morphology, modes of preservation and attributed feeding traces; no trilobite specimen with internal gut contents has been described3,4. Here we present the complete and fully itemized gut contents of an Ordovician trilobite, Bohemolichas incola, preserved three-dimensionally in a siliceous nodule and visualized by synchrotron microtomography. The tightly packed, almost continuous gut fill comprises partly fragmented calcareous shells indicating high feeding intensity. The lack of dissolution of the shells implies a neutral or alkaline environment along the entire length of the intestine supporting digestive enzymes comparable to those in modern crustaceans or chelicerates. Scavengers burrowing into the trilobite carcase targeted soft tissues below the glabella but avoided the gut, suggesting noxious conditions and possibly ongoing enzymatic activity.

The first healed injury in a hyolith operculum.

The Palaeozoic sediments of the Barrandian area are globally well-known as a classic example of rocks characterised by an abundant skeletal marine fauna, including well-preserved remains of hyoliths. Several tens specimens of malformed invertebrates such as trilobites, cephalopods and gastropods have been collected and documented from Cambrian to Devonian clastic sediments and carbonates in this area. However, no malformed hyolith specimen has yet been recorded. Hyoliths are Palaeozoic animals with small calcium carbonate shells composed of the conch (= oblong, conical and bilaterally symmetrical shell of diverse cross section and aperture at its wide end) and the operculum (= cap closing the conch aperture). Here we describe an operculum showing regeneration after non-lethal predatory attack in the Ordovician hyolith Elegantilites custos. This is the first record of regeneration in a hyolith operculum that has been repaired after a failed durophagous attack. Epibenthic/infaunal predatory echinoderms, such as ophiuroids, are considered as potential culprits.

Exoskeletal and eye repair in Dalmanitina socialis (Trilobita): An example of blastemal regeneration in the Ordovician?

OBJECTIVE: To analyze anomalies of a biomineralized exoskeleton of a trilobite. MATERIALS: A specimen of Dalmanitina socialis from the Upper Ordovician Letná Formation at Veselá near Beroun, Czechoslovakia, curated at the Czech Geological Survey in Prague. METHODS: The internal mold and external mold and latex casts were coated with ammonium chloride sublimate and photographed. RESULTS: A substantial reduction of the eye surface associated with changes in morphology and surface structure was noted. CONCLUSIONS: The anomaly is believed to be the result of a healed injury after an unsuccessful predatory attack. Based on the presumed mechanism of injury, a 'large arthropod' is proposed to be the potential attacker. SIGNIFICANCE: The low incidence of sublethal attack to cephala in collections of Cambrian to Carboniferous trilobites implies that most such attacks were fatal, rendering this specimen unique and capable of providing insight into healing processes. LIMITATIONS: Post-mortem damage rendered analysis difficult. SUGGESTIONSFOR FURTHER RESEARCH: Exploration of other cases of healed trauma in order to understand Ordovician ecosystems.