Acritarchous cysts ofPeridinium faeroensePaulsen: Implications for dinoflagellate systematics

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Abstract
The cyst‐based and the theca‐based dinoflagellate classification systems were compared using Peridinium faeroense Paulsen, 1905, and species of Ensiculifera Balech, 1967, Scrippsiella Balech ex A. R. Loeblich III, 1965, and Peridinites Lefèvre, 1933. Cyst differences were more obvious, including “acritarchs”;, and calcareous and siliceous‐walled forms, whereas equivalent thecal differences included only “minor”; features such as cingular and sulcal plate details. This supported Balech's recent subdivision of the genus Peridinium based on these minor thecal features; it also showed that comparable subdivisions were suggested by cyst morphology. The two classification systems appeared more similar than in previous comparisons which neglected such minor thecal features. Both cysts and thecae are considered to be equally valid taxonomic criteria. The implications for dinoflagellate systematics suggested by this are that both cysts, where known, and thecal features should be included in species descriptions establishing a holomorph. Quaternary and Recent cysts should ultimately be classified under a unified system based on the holomorph. In the interim, cyst nomenclature should reflect known paleontologic and biologic information. New cyst‐based nomenclature should not be created just to “artificially”; maintain dual classification.