Thecideide brachiopods from the slope facies of a sponge-cyanobacterial bioherm exposed in theWapienno and Bielawy quarries (Kujawy, Poland) are described. Numerous specimens were found in the upper part of the section, in the Hauffianum-Planula Subzones of the Oxfordian, and constitute the first record of these brachiopods from the Jurassic deposits in the area. Two species: Rioultina wapiennensis sp.nov. and Neothecidella ulmensis QUENSTEDT, 1858, are described, the first being the only representative of the genus Rioultina found in Poland. Excellent preservation of some specimens enabled recognition of details of their internal morphology usually inaccessible in fossil material, including features associated with reproduction and the development of the rachidium. Study of relatively large numbers of thecideides still cemented to the substrate, together with analysis of the associated fauna, allowed the reconstruction of aspects of their ecology.
