Palaeobiological significance of damaged and fragmented thylacocephalan carapaces from the Upper Devonian of Poland Krzysztof Broda, Mateusz Wolny, Michał Zaton´ * University of Silesia, Faculty of Earth Sciences, Be˛dzin´ska 60, 41-200 Sosnowiec, Poland 1. Introduction The Class Thylacocephala Pinna et al., 1982 belong to a group of rather enigmatic marine arthropods which are currently grouped with crustaceans (Lange et al., 2001; Haug et al., 2014). Thylacocephalans are known from the Silurian to the Upper Cretaceous (Schram et al., 1999; Schram, 2014; Haug et al., 2014), but some Lower Cambrian forms classified to thylacocephalans also occur (Vannier et al., 2006). Their geographic distribution is wide, and thylacocephalans are documented from all continents except Antarctica and South America (Hegna et al., 2014). The most characteristic features of thylacocephalans are a bivalved carapace enclosing almost the entire body; large, compound eyes present in many species; three pairs of long, subchalate raptorial appendages on the anterior part of the body; and a series of small, paddle-like limbs in the posterior part (Rolfe, 1985, 1992; Briggs and Rolfe, 1983; Vannier et al., 2006; Charbonnier et al., 2010; Schram, 2014). The mode of life of thylacocephalans was a subject of a debate (see e.g., Rolfe, 1985), but currently it is accepted that at least some species were pelagic predators, as evidenced from their large, spiny raptorial appendages and cuticular pores which might have played a role as bioluminescent photophores (e.g., Secre´ tan, 1985; Rolfe, 1985; Vannier et al., 2006; Charbonnier et al., 2010). The occurrence of some species in deep-water facies, as evidenced from lithology and faunal association (e.g., Charbonnier et al., 2010; Zaton´ et al., 2014), attests to a pelagic life-style. Even the stomach contents, including fish remains or coleoid hooks, found in Lower Jurassic Ostenocaris (Pinna et al., 1985) may indicate that thylacocephalans were active nektonic predators; however, their scavenging mode of life is enigmatic and lacks evidence for or against. Thylacocephalans were also predated upon by various organ- isms. Pinna et al. (1985) found fragmented thylacocephalan cuticle in the stomach contents of other thylacocephalans, and Williams (1990) found a complete carapace within the body cavity of a cladoselachian shark from the Famennian of Ohio. Late Devonian thylacocephalan remains were also detected in numerous gastric residues from the Gogo Formation of Australia by Briggs and Rolfe (1983), and recently fragmented cuticle of Concavicaris were found within some coprolites from the lower Famennian of Poland by Proceedings of the Geologists’ Association xxx (2015) xxx–xxx A R T I C L E I N F O Article history: Received 23 March 2015 Received in revised form 14 May 2015 Accepted 19 May 2015 Available online xxx Keywords: Thylacocephala Arthropods Taphonomy Predation Devonian A B S T R A C T 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. ß 2015 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +48 697122100. E-mail address: mzaton@wnoz.us.edu.pl (M. Zaton´ ). G Model PGEOLA-433; No. of Pages 10 Please cite this article in press as: Broda, K., et al., Palaeobiological significance of damaged and fragmented thylacocephalan carapaces from the Upper Devonian of Poland. Proc. Geol. Assoc. (2015), http://dx.doi.org/10.1016/j.pgeola.2015.05.005 Contents lists available at ScienceDirect Proceedings of the Geologists’ Association jo ur n al ho m ep ag e: www .els evier .c om /lo cat e/p g eo la http://dx.doi.org/10.1016/j.pgeola.2015.05.005 0016-7878/ß 2015 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved.