Epibionts of mollusc shells from the Korycany limestones (Upper Cenomanian, Czech Republic)


Authors: Žítt J, Kopáčová M, Nekovařík Č

Published in: Bulletin of Geosciences, volume 78, issue 1; pages: 41 - 52; Received 17 January 2002; Accepted in revised form 8 July 2002;

Keywords: Gastropoda, Bivalvia, shells, encrusting fauna, internal moulds, taphonomy, Korycany Member, Upper Cenomanian, Bohemian Cretaceous Basin,

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Abundant internal moulds of gastropod shells and imprints of bivalve shells were collected from the Korycany limestones (Korycany Member, Late Cenomanian) exposed in the gas-main excavations near Korycany in central Bohemia. The specimens are unique in that they comprise encrusters of inner shell surfaces, preserved after the shells were diagenetically dissolved or otherwise destructed. The preserved cemented component of an encrusting community consists of oysters, worms and bryozoans. In gastropods, predominantly apertural and adjacent parts of inner shell surfaces were colonized. Oysters, often in preferred orientations, prevail on inner surfaces of bivalve shells. A direction of coiling of oyster shells was proved to be a useful tool for a correct interpretation of the original position of encrusters on the host shells. Taphonomic and palaeobiological features of the encrusters indicate that the postmortem colonization of mollusc shells was only a short-lasting one, with possible slight environmental disturbances and episodic rapid burials. Later formation of gastropod moulds corresponded with shell dissolution and lithification rates of the rock. In this connection, two extreme mould types were distinguished with a series of stages in epibiont preservation between them.