Cochlosoma was first described by Kotlán (1923) to include
C. anatis, a flagellate he found in the intestines of young European domestic ducks (
Anas platyrhynchos) suffering from coccidiosis.
Cochlosoma rostratum was identified in North American domestic ducks by Kimura in 1934, although this species is now recognized as a synonym of
C.anatis. Kimura was the first to describe the
morphology of
Cochlosoma in great detail. A second species was described under the name
Cyanthosoma striatum (Tyzzer, 1930) and was reassigned as
Cochlosoma striatum by Kulda and Nohýnková (1978). In 1938, Bernard V. Travis described two new species of
Cochlosoma,
C. picae and C. turdi. The most recent addition to genus
Cochlosoma is
C. soricis, which was found in
shrews by Watkins et al. (1989).
Cochlosoma was originally proposed to be part of
diplomonads because their prominent adhesive disc is similar to that of
Giardia. In 1952, Grassé placed the genus into the order
Retortamonadida. However, morphological and ultrastructural observations (i.e.
parabasal apparatus, pelta, costa, and axostyle) suggest the genus is more likely related to
trichomonads and in 1996, Pecka et al. moved
Cochlosoma to order Trichomonadida. More recently, analysis of their
rRNA gene sequence further supported their placement in Trichomonadida and led to their transfer from family
Cochlosomatidae to family
Trichomonadidae. == Hosts ==