This class includes the orders Dinophysida and Nannoceratopsida. Although armoured these dino-flagellates lack a distinctive tabulation. The cingulum is anterior in position and less spiralled than in the peridinoids (Peridiniales), uniting with the sulcus in a T- or Y-shaped junction. Both furrows are bordered by flange-like crests, as in the Recent Ornithocercus (Fig. 10.6g). The cysts are proximate, the archaeopyle and operculum epicystal, comprising the whole of the epicyst. Fossil examples are few but may include Nannoceratopsis from the Jurassic (Fig. 10.6f). In this there are normally two prominent antapical horns and a cingular archaeopyle.
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