Middle Cambrian Bivalvia from Bornholm and a review of Cambrian bivalved Mollusca

This is the first record of a Cambrian pelecypod fauna that consists of more than one species. The respective fauna comes from the Middle Cambrian Borregärd Member which is a special development of the Exsulans Limestone on the lsle of Bornholm. Pelecypods are already known from the Early Cambrian, but at that time they are still rather rare. Cambrian pelecypods are generally small and thus occur mostly in microfossil residues. The specimens described herein were picked from etched residues and belang to three genera (one new) and three new species or subspecies, respectively. The original shell of the pelecypods is mostly missing, but the fine inner and outer phosphatic coating reflects the outer shell characteristics in great detail. Steinkern preservation additionally shows relics of muscle attachment and the pallial line. All three taxa have beautifully preserved taxodont hinges. For comparative reasons the Australian Middle Cambrian Pseudomyona queens/andica is included. The main characteristics of Cambrian pelecypods are compared with each other and ideas of how pelecypods developed are briefly discussed. New taxa are Pojetaia ostseensis n.sp„ Tuarangia gravgaerdensis tenuiumbonata n.ssp„ and Camya asy n.gen„ n.sp.