Fossilized soft tissues in Palaeozoic bryozoans

Thin sections of three Palaeozoic bryozoans reveal fossilized soft tissues that show the position of organic cuticle and internal structures such as the membranous sac and gut. The fossilization occurred apparently due to fast burial under anoxic conditions. The position of a membranous sac in the Permian trepostome Rhombotrypella superangustata is indicative of a progressive polypide cycle. The position of the polypide in the Ordovician Graptodictya delicata behind the superior and interior hemisepta suggests a protective function of the hemisepta.