What is an opsithokont?

Opsithokonts are a clade of eukaryotic organisms that includes animals, fungi, and several groups of protists. They are characterized by their posterior flagellum in their motile cells, a feature that distinguishes them from other eukaryotic groups. This clade plays a crucial role in the evolution of multicellular life, as it encompasses both the animal and fungal kingdoms. The term "opsithokont" is derived from Greek, meaning "posterior pole," referring to the location of the flagellum.