Investigating a Devonian vertebrate assemblage with synchrotron microtomography of coprolites.

Fossilised faeces (coprolites) are a unique source of information as they record palaeontological evidence of animal behaviour (autecology) as well as interactions between extinct organisms and their environment (synecology). Four samples bearing coprolites found in a newly discovered vertebrate locality in the Kumushka Formation dated to the Givetian-Frasnian transitional interval of the Devonian sequence of North Timan (NE Europe) were scanned using propagation phase-contrast synchrotron microtomography. A total of seven coprolites were recovered and segmented to digitally extract their entire internal contents. The three-dimensional preservation of the inclusions allowed for their anatomical and taxonomical identification. Acanthodian and fleurantiid-like dipnoan remains are abundantly found in every sample, along with fewer holoptychiid sarcopterygian elements. The contents of the coprolites indicates an opportunistic feeding behaviour, with remains from multiple trophic levels present across the different samples. The size of some remains reveals feeding on juveniles. Sarcopterygians Eusthenopteron, Laccognathus and Glyptolepis are inferred to be potential producers of the coprolites based on their sizes, morphologies, inclusions and their internal architecture. The taxa preserved within the studied coprolites and from body fossil remains, are placed in a trophic pyramid, providing evidence for the early establishment of a complex multi-level trophic chain at the Givetian-Frasnian transition.