Palaeobiological significance of damaged and fragmented thylacocephalan carapaces from the Upper Devonian of Poland

This paper investigates thylacocephalan (?Crustacea) carapaces from the lower Famennian of the Holy Cross Mountains, Poland in order to check whether predation-related activities has influenced the mode of carapace preservation. Analysis of 225 specimens reveals that 71% of carapaces consist of complete/nearly complete specimens, and those that are incomplete have experienced purely taphonomic processes. The remaining 29% of specimens, are damaged and fragmented carapaces, the preservation patterns of which point to biological modifications due to predation. These damaged carapaces range from those that have some portions missing, to those totally fragmented into small pieces scattered on bedding planes. The damaged specimens lacking some portions of the carapace are similar to those described previously from the Frasnian of Australia, where they are interpreted to evidence fish predation. The loosely scattered cuticle fragments are very similar to those reported from the Pennsylvanian of the USA that are interpreted as shark regurgitates. We interpret the damaged and fragmented thylacocephalans from Poland as evidence for fish predation, consistent with previous evidence from fragmented cuticle preserved within coprolites. However, as the majority of cuticle fragments occurring within coprolites in previous studies are difficult to distinguish, the simple calculation of predation intensity is much lower (13%) to that obtained in the present study (29%). Thus, analysis of thylacocephalan carapace preservation conducted here, may serve as a calibrating tool for the assessment of a general predation intensity in a given palaeoenvironment based solely on coprolite data.