Article: Palaeoperidinium cretaceum: a brackish-water peridiniinean dinoflagellate from the early Cretaceous

New SEM observations of topotype material of Palaeoperidinium cretaceum from the early Cretaceous of Alberta, Canada have allowed a complete description of this poorly known morphotype, including tabulation and plate overlap patterns. The features displayed by P. cretaceum show that, unlike other members of the genus, this morphotype cannot be interpreted as an extrathecal 'exophragm'. The life-cycle stage represented by P. cretaceum is discussed in relation to the life-cycle of modern dinoflagellates. It is suggested that P. cretaceum may represent a hitherto unknown fossilizable zygotic stage in the dinoflagellate life-cycle.