Trends in shell fragmentation as evidence of mid-Paleozoic changes in marine predation

Abstract

Recent observations indicate that shell fragmentation can be a useful tool in assessing crushing predation in marine communities. However, criteria for recognizing shell breakage caused by durophagous predators versus physical factors are still not well established. Here, we provide data from tumbling and aquarium experiments to argue that physical and biotic processes lead to different patterns of shell damage, specifically that angular shell fragments are good indicators of durophagous predation. Using such angular shell fragments as a predation proxy, we analyze data from 57 European Paleozoic localities spanning the Ordovician through the Mississippian. Our results reveal a significant increase in angular shell fragments (either occurring as isolated valves or present in regurgitalites) in the Mississippian. The timing of this increase is coincident with the increased diversity of crushing predators as well as marked anti-predatory changes in the architecture and mode of life of invertebrate prey observed after the end-Devonian Hangenberg extinction (359 Ma). More specifically, the observed trend in shell fragmentation constitutes strong and independent confirmation of a recently suggested end-Devonian changeover in the primary method of fish predation from shearing to crushing. These results also highlight the important effect of extinction events, not only on taxonomic diversity, but also on the nature of predator-prey interactions.

Experimental tumbling of Dreissena polymorpha: implications for recognizing durophagous predation in the fossil record

“…Salamon et al 2014) and crabs (Eriphia verrucosa) feeding on Dreissena polymorpha and Mytilus sp. respectively, revealed that these predators induce fragmentation into larger (> 2 mm) sharp-edged shell pieces displaying extremely low roundness and varying degree of sphericity (Fig.…”

“…They are an invaluable source of information about predator-prey interactions in the fossil record (e.g., Zatoń and Salamon 2008;Salamon et al 2014). However, in contrast to coprolites, which are relatively easy to recognize in the fossil record (from the external spiral folding and/or vascular markings reflecting the morphology of the predator intestine, and containing the skeletal particles partly affected by digestion that are usually dispersed within calcium phosphate matrix, e.g., Pollard 1990), the identification of regurgitalites is very difficult.…”

“…Various types of shell damage due to water agitation (such as near-shore waves, currents, and tidal action) have been studied both in natural environments (e.g., Walther 1910;Kidwell and Bosence 1991;Cadée 1968Cadée , 1994Cadée , 1995Cadée , 2016Leighton et al 2016) and in laboratory conditions (e.g., Müller 1951Müller , 1976Kuenen 1966a, b;Chave 1964;Driscoll 1967Driscoll , 1970Oji et al 2003;Chojnacki and Leighton 2013;Salamon et al 2014). In general, it has been argued that transported shells are infrequently broken and possess abraded surfaces and rounded margins.…”

“…In contrast, angular shell fragments with sharp margins are typically considered a good proxy for durophagous predation (e.g., Cintra-Buenrostro 2007; Salamon et al 2014). Interestingly, Oji et al (2003) have argued that durophagous predation intensity, as measured by the frequency of occurrences of angular shell fragments in fossil shell beds, increased during the early Cenozoic, coinciding with the radiation of durophagous teleost fish and decapod crustaceans.…”

“…Likewise, Salamon et al (2012) documented numerous regurgitalites from the Middle Triassic and suggested that many morphological and behavioral innovations in the Triassic benthic fauna are escalation-related adaptations to durophagous predators. Using angular shell fragments as a predation proxy, Salamon et al (2014) also analyzed data from many European Paleozoic localities spanning the Ordovician to the Carboniferous. The results of the latter authors showed a significant increase in angular shell fragments of molluscs and brachiopods in the Mississippian.…”