| Cavalier-Smith and Chao (2003) present a scenario in which the unikonts, those organisms with single flagella, are paraphyletic. They root the eukaryotes in a line from a group of Gram positive eubacteria, which gave rise to the eukaryotes and the archaea. The stages in the origin of the eukaryote line were the organization of microtubules to form a flagellum (not the endosymbiotic origin as Margulis claims) and the later acquisition of a mitochondrial endosymbiont. The single flagellar structure gave rise to the Opisthokonts (taxa with a single trailing or pushing flagellum and flat mitochondrial cristae) and the Anterokonts (taxa with a single anterior or pulling flagellum and tubular mitochondrial cristae). The anterokonts (e.g. Amoebozoae) gave rise to the Bikont line, which they presumed to have arisen through an apusozoan-like organism. See Cavalier-Smith (2003) for an elaboration on this scenario. |
