A hermeneutic analysis of the shell-drilling gastropod predation on mollusks in the Korytnica Clays (Middle Miocene; Holy Cross Mountains, Central Poland)

Abstract

Shell-drilling predation by naticid and muricid gastropods on mollusks has been studied in the fossil assemblage of the Korytnica Clays (Middle Miocene; Holy Cross Mountains, Central Poland). To this end, the hermeneutic method has been employed, which begins with a pre-understanding of a natural phenomenon, then proceeds with data analysis, thus leading to improved understanding, etc. Three large bulk samples have been analysed, each of them consisting of two spatially adjacent subsamples; these samples cover much of the paleosynecological variability discovered previously in the Korytnica Clays. Sample representativeness analysis did not reject the null hypothesis of subsample identity (and hence sample representativeness) in two of three considered samples; for the third one, its subsamples have been consequently analysed separately from each other. Taphonomic analysis focused on the preservation condition of mollusk shells, left-to-right valve ratio among mollusks, bivalve articulation and gastropod preservation, scaphopod preservation, and size-frequency distribution of a number of species. This analysis leads to the conclusion that fossils experienced only local post-mortem transportation, virtually no chemical dissolution, and very little time-averaging, except for the one nonrepresentative sample. Fossil fragmentation is mostly due to compaction. Prey analysis has largely focused on the bivalve Corbula gibba and the gastropod Nassa hoernesi, which has been commonly drilled. Predator analysis concerned both naticid and muricid gastropods. Quantitatively, prey-size preference by the predators, drillhole location distributions, and predation efficiency have been studied, whereas some other questions, such as the preference hierarchy of prey species by the predators could be addressed only qualitatively. Beyond the conclusions concerning the fossil assemblage of the Korytnica Clays, the study also points to the inevitable limitations of qualitative paleoecological inference.