Abstract. A new species of dinoflagellate, Eodinia poulseni, is described from the Middle Jurassic of Central Poland. Light and scaning electron microscopy shows that this species has a complex cyst wall consisting of autophragm and ectophragm. Eodinia poulseni sp. nov. has similarities to some common Middle Jurassic species, especially when separate hypocysts are observed. Important differences between Eodinia pachytheca, Mosaicodinium mosaicum, Wanaea acollaris, W. cornucavata and Hurlandsia rugarum are discussed. Some phylogenetic and environmental relationships to the Early Cretaceous freshwater species Hurlandsia rugarum are suggested. H. rugarum shows similarity in archaeopyle, overall shape and tabulation formula but is acavate and also distinct from E. poulseni in time.