Evolution and Motility of Blastozoan Echinoderm Stalks in the Ordovician of the Baltic Paleobasin

Blastozoan and crinozoan echinoderms are studied from the Ordovician of the Baltic Paleobasin providing evidence for comparative aspects of their evolution. The study particularly focused on heteromorphic stems of three genera of the superfamily Glyptocystitoida from the Middle Ordovician of the Leningrad Region, examining their possible motility in comparison with stem motility data on Laurentian Pleurocystitidae.