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Borings in Cloudina Shells: Complex Predator-Prey Dynamics in the Terminal Neoproterozoic

¹ Key Laboratory of Continental Dynamics, Ministry of Education, and Department of Geology, Northwest University, Xi’an, Shaanxi 710069, China
² Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada, brian.pratt{at}usask.ca
³ Xi’an Institute of Geology and Mineral Resources, Ministry of Land and Resources, Xi’an, Shaanxi 710054, China

ABSTRACT

Predation as an important driver of evolutionary change long has been assumed, despite difficulties to substantiate it with specific examples of predatory interaction, especially for the early Paleozoic diversification of animal life. This study corroborates the existence of shell-drilling predation in the uppermost Neoproterozoic of China. Nearly one-fifth of almost one hundred tubular shells of one of the earliest mineralized animals, Cloudina, are perforated by undoubted predatory borings 15–85 µm wide. By contrast, no specimens of co-occurring shells belonging to Sinotubulites were affected. The identity of the predator remains elusive, but variation in size of the borings suggests a predatory lifestyle throughout its growth, after it reached a minimum size. The relatively uniform distance of the borings from the shell apertures points to either control by the life orientation of the shells, such as the position of the sediment surface, or, more likely, an avoidance response by the predator to protective measures located near the aperture. Assuming Sinotubulites had similar life habits and was potential prey, the absence of borings in this taxon is evidence that these tubes may have been protected by organic material or toxins that fended off shell-drilling predators. Hence, this earliest example of predation in the fossil record already shows prey selectivity and site-specific behavior, pointing to a level of Precambrian predator-prey interaction that approaches the complexity seen in younger Paleozoic benthic animal communities. This is consistent with the suggestion that predation was indeed an active contributor to the Cambrian radiations.