Chromalveolata is a eukaryote supergroup present in a major classification of 2005, then regarded as one of the six major groups within the eukaryotes. It is a refinement of the kingdom Chromista, first proposed by Thomas Cavalier-Smith in 1981. Chromalveolata was proposed to represent the organisms descended from a single secondary endosymbiosis involving a red alga and a bikont. The plastids in these organisms are those that contain chlorophyll c.