Balech (1958a: 82, pl. 2, figs 14–25), as antarcticum
Balech (1976: 29, fig. 18), Andreoli et al. (1995: 473, fig. 18)
Cells rounded to elliptical in side view, 28–65 µm long, 20–55 µm diameter. Epitheca very low and generally flat. Sulcal lists smooth; left sulcal list always narrow at the lower septal ray (R3); right sulcal list reduced. Cell surface covered with areolae and scattered pores; additional apical or antapical projections (excrescences) absent. Chloroplasts present.
Southern Ocean, south of Australia; Terra Nova Bay, Ross Sea (Andreoli et al., 1995); Southern Ocean, near South Georgia (Dodge & Priddle, 1987); Bellingshausen Sea (Balech, 1973); Weddell Sea, Antarctic Peninsula (Balech, 1973, 1975).
Dinophysis is a distinctive genus with up to ten representatives in the Southern Ocean. While diversity is lower than in many other marine environments, occasionally species of Dinophysis have been observed to dominate Southern Ocean dinoflagellate floras (Dodge & Priddle, 1987).The genus is characterised by a small rounded to flat epitheca and a much larger, rounded to elliptical hypotheca. The cingulum is well defined and bordered by prominent lists. Lists are also associated with the sulcus which, because of the lenticular shape of the cell, are usually located on the side.Many authors consider Phalacroma to be synonymous with Dinophysis (e.g. Tai & Skogsberg, 1934; Abé, 1967). The genera overlap in many aspects of their morphology, but can be separated the distinctive, funnel-shaped, anterior cingular list of Dinophysis. Other features, such as the development and direction of cingular lists in combination with the height and shape of the epitheca, also help to distinguish the genera. Members of the genus Dinophysis are specialised predators, and Hansen (1991) observed D. rotundata Clap. & J.Lachm. (= Phalacroma rotundatum ) and D. hastata Stein ingesting the prostomatid ciliate Tiarina fusus< /EM> (Clap. & J.Lachm.) Bergh.
Dinophysis antarctica can be distinguished from most other Antarctic species by its flat epitheca and lack of excrescences. The otherwise similar D. punctata is much smaller, while D. meteori is almost rectangular in shape. This species has been observed only infrequently in eastern Antarctica, some specimens being somewhat smaller than previously reported.