 Dinoflagellates are algae and according to recent phylogeny they are sister groups to ciliates and apicomplexans.Most phylogenetic studies are done with sequences of both large and small ribosomal subunits and do not always agree with morphological studies based on thecal plates.Sequencing of the small subunit of the ribosome of "Dinophysis" revealed very similar sequences in three species of "Dinophysis" ("D. acuminata", "D. norvegica" and "D. acuta"), suggesting that photosynthetic "Dinophysis" have evolved recently.