Behavioural palaeobiology and taphonomy of the Late Jurassic calcareous sponge Elasmostoma fomes W. Müller, 1984

Abstract

Calcareous sponges Elastostoma fomes W. Müller, 1984, from the Lower Kimmeridgian marly onkoliticlimestones exposed at Karsy in the Holy Cross Mountains, Central Poland, are studied in terms of their settlement, growth, behaviour, and resulting phenotypy. The lichen-shaped auriculate specimens are interpreted as growing upwardly, at a higher angle to the bottom surface, in order to involve passive flow carrying suspended nutrients up on which they fed. Unstable bottom and hydrodynamic conditions, under which the growth of sponges progressed, were basic prerequisites that controlled ecophenotypic variability of the studied specimens. A peculiar case of regeneration is discussed, to postulate the skeleton parts having been lithified during the sponge's life, and healed after an accidental injury. Aviolent event that caused catastrophic burial of the studied sponge assemblage is ascribed to high-energy agents, most likely of storm origin.