The oldest arthropods of the East European Platform

Cassubia Lendzion 1977 and Liwia new name (for Livia Lendzion 1975 preoccupied) found in the subsurface Zawiszany formation of the basal Cambrian in NE Poland are identified as an anomalocarid and a ‘soft-bodied’ trilobite, respectively, each being the oldest representative of its group. The presence of four free thoracic tergites in Liwia, the relatively strong sclerotization, and the apparent segmentation of the pygidial shield (expressed in the metameric distribution of marginal spines) indicate that the ‘soft-bodied’ trilobites achieved their organization by secondary softening of the dorsal exoskeleton and suppression of the development of thoracic tergites in ontogeny.