sentences:  The first mention of cryptophytes 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.