The genus was created by Lainson, Landau and Shaw in 1974. A revision of the genus Plasmodium by Levine in 1985 considered this subgenus to be a synonym of Plasmodium. The description of a new species Plasmodium siamense by Telford in 1986 lead to a resurrection of this as a subgenus. Further revision of its taxonomic status has led to its elevation to genus status.
There are two recognised subgena - Fallisia Telford 1998 and Plasmodiodes Gabaldon, Ulloa & Zerpa 1985. Species in Fallisia infect lizards and those in Plasmodiodes infect birds.
Until confirmed by molecular methods this classification should be regarded as tentative.