Archezoa was a kingdom proposed by Thomas 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 mitochondriate ancestors, and trees based on other genes do not support their basal placement. The kingdom Archezoa has therefore been abandoned.