Archezoa

Archezoa was a kingdom proposed by Cavalier-Smith for eukaryotes that diverged before the origin of mitochondria. At various times, the pelobionts and entamoebids (now archamoebae), the metamonads, and the microsporidia were included here. These groups appear near the base of eukaryotic evolution on rRNA trees. However, all these groups are now known to have developed from mitochondrial ancestors, and trees based on other genes do not support their basal placement. The kingdom Archezoa has therefore been abandoned.
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One of the kingdom level taxons proposed by Cavallier-Smith which consists of the most ancient unicellular eukaryotes with a nucleus and rod shaped chromosome but no mitochondria or plastid, thus believed to be the intermediate stage between prokaryotes and eukaryotes. They are also used as evidence for the evolution of nucleus before the organelles. The intestinal parasite Giardia lamblia (a protist) is an example.