Pinguiochrysidaceae is a family of marine Heterokontophyta. It is the only family in the order Pinguiochrysidales, which is the only order in the class Pinguiophyceae. It includes five species of unicellular organisms with high concentration of polyunsaturated fatty acids in the cytoplasm. The other common features are the lack of cell wall and the tendency for flagella loss even on the stage of zoospore, which is unusual for heterokonts. One species inhabits benthic substates and is able to produce lorica with one or more tubular necks. The other species live in the plankton.
A protist is any eukaryotic organism that is not an animal, plant, or fungus. The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; but, like algae or invertebrates, the grouping is used for convenience. In some systems of biological classification, such as the popular five-kingdom scheme proposed by Robert Whittaker in 1969, the protists make up a kingdom called Protista, composed of "organisms which are unicellular or unicellular-colonial and which form no tissues". In the 21st century, the classification shifted toward a two-kingdom system of protists: Chromista and Protozoa.
