Algal taxonomy

The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of unicellular algae found in freshwater and moist terrestrial environments, less common today than they were during the Proterozoic. The stated number of species in the group varies from about 14 to 26. Together with the much larger sister taxa Rhodophyta (red algae) and Viridiplantae/Chloroplastida (green algae and land plants), they form the primary algae clade Archaeplastida.

Euglenids or euglenoids are one of the best-known groups of eukaryotic flagellates: single-celled organisms with flagella, or whip-like tails. They are classified in the phylum Euglenozoa, class Euglenida or Euglenoidea. Euglenids are commonly found in fresh water, especially when it is rich in organic materials, but they have a few marine and endosymbiotic members. Many euglenids feed by phagocytosis, or strictly by diffusion. A monophyletic subgroup known as Euglenophyceae have chloroplasts and produce their own food through photosynthesis. This group contains the carbohydrate paramylon.

The haptophytes, classified either as the Haptophytina, Haptophyta or Prymnesiophyta (named for Prymnesium), are a clade of algae that can produce minerals.

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Biliphyta is an obsolete polyphyletic subkingdom of algae.