Operational taxonomy and (paleo-)autecology of round, brown, spiny dinoflagellate cysts from the Quaternary of high northern latitudes

Round brown spiny dinoflagellate cysts from high latitudes of the Northern Hemisphere have been examined in order to define criteria for their determination during routine counts. The round brown spiny cysts belong to several taxa including the paleontological genera Echinidinium and Islandinium and the biological genera Oblea, Polykrikos, and Protoperidinium. Here, we present a synthesis of descriptions with remarks on the morphology, taxonomy, nomenclature and ecology of cysts from the observations of samples collected in high latitude environments. These observations have led us to establish a practical identification key based on the most distinct morphological features that characterize all specimens. These features exclude the archeopyle, which is rarely observed. Two new cyst types are described from Holocene and Pleistocene sediments of the North Pacific and North Atlantic oceans, respectively. The identification key permits the following to be distinguished: “Echinidinium aculeatum”, Echinidinium delicatum, Echinidinium granulatum, Echinidinium karaense, Echinidinium sleipnerensis, Echinidinium “transparantum”/zonneveldiae, Islandinium brevispinosum, Islandinium? cezare, and Islandinium minutum, the cysts of Oblea acanthocysta and Polykrikos hartmannii (al. Pheopolykrikos hartmannii), and the new cyst types Echinidinium? sp. A and Echinidinium? sp. B.

► We establish a taxonomical determination key for the round brown spiny dinocysts.
► The determination of round brown spiny dinocysts deserves special attention.
► Species of Echinidinium and Islandinium are sensitive to sea surface conditions.
► Round brown spiny dinocysts are abundant in high latitude environments.