Lower to Middle Oxfordian sponges of the Polish Jura

Abstract

Sponges predominate in the benthic fauna of the Oxfordian Jasna Góra Beds (cordatum and plicatilis Zones) of the Polish Jura, south Central Poland, making part of the European Upper Jurassic sponge megafacies. The Jasna Góra Beds comprise sponges mostly in bedded limestones, while bioherms occur but occasionally. The analysed assemblage includes 12 species of the Lithistida, 16 species of the Hyalospongea, and also non-lithistid demosponges represented by isolated spicules. The assemblage differs from that one found in the White Jurassic a of Swabia and Franconia, a facies equivalent of the Jasna Góra Beds, as the former is dominated by the Lithistida, while the latter by the Hyalospongea. The investigated sponges inhabited a deeper-shelf environment, not shallower than 150–200 m; they seem to have been slightly implanted in the soft bottom sediment. The sponge assemblage is species diverse in marly beds, but highly dominated by a single species in limestones. Sponge bioherms developed mostly at local slopes of the bottom, due to an improved water circulation.
The systematic part of the paper includes descriptions of 28 species, those represented by the material sufficiently rich to permit a departure from the pre-existing oversplitted taxonomy and a recognition of their proper taxonomic position.