Scanning electron microscope image of the epicyst of Nannoceratopsis

Scanning electron microscope image of the epicyst of Nannoceratopsis, showing minute plates arranged in a peridinialean pattern.

Nannoceratopsis is in many respects an unusual dinoflagellate cyst. 

The overall morphology with its large, laterally compressed hypocyst is strikingly different to all other fossil dinoflagellate cysts. However, it is reminiscent of the thecae of modern Dinophysiales and Prorocentrales, although these orders do not form preservable cysts and have no fossil record.

The tabulation in Nannoceratopsis shows a combination of characters otherwise typical of two very different dinoflagellate orders, the Dinophysiales and the Peridiniales:

  • The tabulation on the hypocyst shows a dinophysialean pattern.
  • The tabulation on the epicyst shows a peridinialean pattern with 2 latitudinal series of minute plates. 

It has therefore been suggested that the Jurassic Nannoceratopsiales are the ancestors from which the modern Dinophysiales evolved.