Occurrence and paleoecological significance of lyssacinosid sponges in the Upper Cretaceous deposits of southern Poland

Cretaceous lyssacinosid sponges (Hexactinellida) are rare and poorly recognized. This is the first description of lyssacinosid sponges from the Cretaceous of Poland. The sponges (including six species and three types of root tufts) come from the Upper Turonian-Lower Coniacian of the Opole Trough, Upper Campanian of the Miechów synclinorium, and Upper Campanian of the SE part of the border synclinorium. All localities lie southwards of the previous reports, widening thus the paleogeographic distribution of the group within the North European Province. Cretaceous lyssacinosids seem to be a useful tool in paleoecological interpretations. The presence of thin-walled lyssacinosids with root tufts indicates a soft substrate, slow rate of sedimentation, and calm and deeper water conditions.