Abstract: Calcareous dinoflagellates have been recorded from subarctic to tropical areas, inhabiting both neritic and oceanic regions. In the present study we analyse 12 sediment samples from the China Sea to establish the existence of calcareous dinoflagellates in this area. A total of 11 calcareous dinoflagellate species were recorded, among them, three genera (Calciodinellum, Leonella, Posoniella) and seven species (Calciodinellum albatrosianum, C. levantinum, C. operosum, Leonella granifera, Posoniella tricarinelloides, Scrippsiella irregularis, and S. regalis) were reported from the China Sea for the first time. Cysts of S. irregularis and S. precaria are identical, with a mesoepicystal archeopyle, representing the loss of 2–4′ and 1–3a paraplates; however, their thecal plates vary slightly and differ from each other in 78 positions of the internal transcribed spacer sequence. Scrippsiella trochoidea is dominant in coastal areas, whereas Calciodinellum albatrosianum is the most abundant offshore. Scrippsiella irregularis is distributed widely along the coast of China, whereas S. precaria is recorded only in northern China. Leonella granifera is the second most abundant species offshore, comprising 15–40% of the cyst assemblage.

Key words: Calcareous dinoflagellates, Calciodinellum, China Sea, Leonella, Posoniella, Scrippsiella.