A relatively small and generally rather compact group of protozoa in the subphylum Sporozoa. Authorities differ as to the group's taxonomic status; that assigned it by the Committee on Taxonomy and Taxonomic Problems of the Society of Protozoologists is followed here: a suborder of the order Eucoccida, subclass Coccidia, class Telosporea, subphylum Sporozoa. The Haemosporina are common protozoan parasites of vertebrates, and some of them are important as causes of illness and death. The best known of the group are the four species of malarial parasites of humans. Not so well known are at least 60 other species of malarial parasites, with a wide host distribution among terrestrial vertebrates, as well as numerous species of Haemoproteus and Leucocytozoon, and some species of Hepatocystis. All three genera are closely related to the genus Plasmodium, in which all the true malarial parasites are placed (see table).