Some aspects of the biology of fossil solid-branching demosponges, exemplified by Reiswigia ramosa gen. n., sp. n., from the Lower Oxfordian of Poland

Abstract

A new demosponge, Reiswigia ramosa gen. n., sp. n., recognized in the Lower Oxfordian deposits of the Polish Jura Chain and· analysed in terms of its taxonomy and biology, represents the solid-branching type of sponge morphology; The functional analysis of various sponge-morphological types permits a de-termination of their significance for current-energy analysis. The very nature of sponge dependence upon current energy consists in (i) resistance of sponges to destructive activities of currents, and (ii) relationship of both the diameter and angle of supply of sponges to currents. The evolutionary transition of solid-en-crusting sponges into the solid-branching ones is discussed in the light of current-induced flow through sponges and life conditions in a boundary layer near the bottom surface.