The name Chrysodidymus means "golden twin" - an apt description of the uncommon and unusual algae that bear this name.

The single recognized species, C. synuroideus Prowse, 1962, has been found in acidic bogs and similar aquatic habitats in Asia, Australia and the Americas. The "colonies" formed by this species consist of two cells joined at the posterior end. Inevitably, comparisons have been made with the pushmi-pullyu of Dr. Dolittle fame. This colony form is the true morphology of the species and not an aberrant growth form as had been supposed before detailed studies were published in the 1990s.

The cells are covered with delicately-sculptured scales that are made of amorphous silica (silicon dioxide; "glass"). Several protistan species make such scales; the patterns found on them are species-specific and are used in identification. The scales are also preserved in sediments, where they fall after the death of the organism. Analysis of the scales preserved in undisturbed sediments provides a record of physical, chemical and biological changes in that body of water over time periods ranging up to a few thousand years before present.

Chrysodidymus belongs to a group of golden algae that botanists call "chrysophytes" and zoologists term "chrysomonads". Specifically, the genus is a member of the "synurophyte" subset of chrysophytes, all of which are silica-scale-forming unicellular or colonial algae. Chrysodidymus synuroideus is the first "synurophyte" that has proven amenable to organelle genomics research.

In turn, the chrysophytes/chrysomonads belong to a large, presumably monophyletic assemblage of algae, fungi and protozoa that has been called "chromists", "heterokonts" or "stramenopiles".

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