Cryptomonad
Classification

The first mention of cryptomonads appears to have been made by Christian Gottfried Ehrenberg in 1831, while studying Infusoria. Later, botanists treated them as a separate algae group, class Cryptophyceae or division Cryptophyta, while zoologists treated them as the flagellate protozoa order Cryptomonadina. In some classifications, the cryptomonads were considered close relatives of the dinoflagellates because of their (seemingly) similar pigmentation, being grouped as the Pyrrhophyta. Cryptomonad chloroplasts are closely related to those of the heterokonts and haptophytes, and the three groups were united by Cavalier-Smith as the Chromista. However, the case that the organisms themselves are closely related was counter-indicated by the major differences in cell organization (ultrastructural identity), suggesting that the three major lineages assigned to the chromists had acquired plastids independently, and that chromists are polyphyletic. The perspective that cryptomonads are primitively heterotrophic and secondarily acquired chloroplasts, is supported by molecular evidence. Parfrey et al. and Burki et al. placed Cryptophyceae as a sister clade to the Green Algae, or green algae plus glaucophytes. The sister group to the cryptomonads is likely the kathablepharids (also referred to as katablepharids), a group of flagellates that also have ejectisomes.

One suggested grouping is as follows: (1) Cryptomonas, (2) Chroomonas / Komma and Hemiselmis, (3) Rhodomonas / Rhinomonas / Storeatula, (4) Guillardia / Hanusia, (5) Geminigera / Plagioselmis / Teleaulax, (6) Proteomonas sulcata, (7) Falcomonas daucoides.
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