The opisthokonts (from Ancient Greek ὀπίσθιος (opísthios) 'rear, posterior' and κοντός (kontós) 'pole, i.e. flagellum') are a broad group of eukaryotes, including both the animal and fungus kingdoms.

[7][8][9][10][11] A common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and the spores of the chytrid fungi, propel themselves with a single posterior flagellum.

[12] The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987,[3] who used the informal name opisthokonta (the formal name has been used for the chytrids by Copeland in 1956), and was supported by later genetic studies.

[citation needed] The following phylogenetic tree indicates the evolutionary relationships between the different opisthokont lineages, and the time divergence of the clades in millions of years ago (Mya).

[17][18][19] Amoebozoa Breviatea Apusomonadida Nucleariae True Fungi Aphelida Rozellida Microsporidia Ichthyosporea Corallochytrium Syssomonas Tunicaraptor Filasterea Choanoflagellatea Metazoa