|Retortamonas (Retortamonadida), on left;
Hexamita, on center, and Giardia, on right (both Diplomonadida)
The retortamonads are a small group of flagellates, most commonly found in the intestines of animals as commensals, although a free-living species called the Chilomastix cuspidata exists. They are grouped under the taxon, Archezoa. They are usually around 5-20 μm in length, and all of their small subunit ribosomal RNA gene sequences are very similar to each other. There are two genera: Retortamonas with two flagella, and Chilomastix with four. In both cases there are four basal bodies anterior to a prominent feeding groove, and one flagellum is directed back through the cell, emerging from the groove.
The retortamonads lack mitochondria, golgi apparatus, dictyosomes, and peroxisomes. They are close relatives of the diplomonads, and are placed among the metamonads along with them. Due to the abundant phylogenetic similarities between the two flagellates, since diplomonads do not ancestrally lack mitochondrion, this suggests that retortamonads are also secondarily amitochondriate.
- Silberman, Jeffrey; Simpson, Alastair; Kula, Jaroslav (31 January 2002). "Retortamonad Flagellates are Closely Related to Diplomonads— Implications for the History of Mitochondrial Function in Eukaryote Evolution". Oxford Journals. 19 (5): 777–786. PMID 11961110. doi:10.1093/oxfordjournals.molbev.a004135. Retrieved 12 February 2015.
- Simpson AG, Roger AJ, Silberman JD, et al. (October 2002). "Evolutionary history of "early-diverging" eukaryotes: the excavate taxon Carpediemonas is a close relative of Giardia". Mol. Biol. Evol. 19 (10): 1782–91. PMID 12270904. doi:10.1093/oxfordjournals.molbev.a004000.
Silberman, Jeffrey; Simpson, Alastair; Kulda, Jaroslav (May 2002). "Retortamonad Flagellates are Closely Related to Diplomonads— Implications for the History of Mitochondrial Function in Eukaryote Evolution". MOLECULAR BIOLOGY AND EVOLUTION. 19 (5): 777–786. PMID 11961110. doi:10.1093/oxfordjournals.molbev.a004135.