Archigregarinorida

Intestinal parasites of marine invertebrates, especially polychaetes.

Family: Selenidioididae

Genera: Selenidioides (synonymised with Selenidium by recent authors), Meroselenidium and Merogregarina.

Family: Exoschizonidae

One genus: Exoschizon

Eugregarinorida (eugregarines)

Blastogregarinorina

A single species, found in marine polychaetes.

Aseptatorina

About 72 genera and 489 species known worldwide.

Family: Selenidiidae

Genera: Digyalum, Selenidium (in sipunculids and polychaetes), Selenocystis, Ditrypanocystis (in earthworms [Oligochaeta]) and Heterospora

Family: Lecudinidae

Genera: Lecudina, Cygnicollum, Loxomorpha, Polyrhabdina, Ulivina, Sycia, Pontesia, Bhatiella, Viviera, Cochleomeritus, Ancora, Hentschelia, Lecythion, Hyperidion, Zygosoma, Filipodium, Diplauxis, Chlamydocystis, Contoriocorpa, Lankesteria, Monocystella, Ascogregarina, Kofoidina, Ophioidina, Paraophioidina, Lateroprotomeritus and Extremocystis

Family: Urosporidae

Genera: Urospora (in sea cucumbers [Holothuria]), Gonospora, Lithocystis, Ceratospora, Pterospora, Paragonospora

Family: Aikinetocystidae

Genera: Aikinetocystis and Nellocystis

Family: Monocystidae

Subfamily: Monocystinae

Genera: Monocystis, Nematocystis, Rhabdocystis, Apolocystis, Cephalocystis, Trigonepimerus and Mastocystis

Subfamily: Zygocystinae

Genera: Zygocystis, Adelphocystis and Pleurocystis

Subfamily: Rhynchocystinae

Genera: Rhynchocystis, Dirhynchocystis and Grayallia

Subfamily: Stomatophorinae

Genera: Stomatophora, Craterocystis, Astrocystella, Albertisella, Beccaricystis, Parachoanocystoides, Choanocystoides, Zeylanocystis, Arborocystis and Chakravartiella

Subfamily: Oligochaetocystinae

Genera: Oligochaetocystis, Echiurocystis, Neomonocystis and Acarogregarina

Family: Diplocystidae

One genus: Diplocystis

Family: Allantocystidae

One genus: Allantocystis

Family: Schaudinnellidae

One genus: Schaudinnella

Family: Enterocystidae

One genus: Enterocystis

Family: Ganymedidae

One genus: Ganymedes

Septatorina

About 151 genera and 1166 species known worldwide. Found in invertebrates, mainly arthropods.

Porosporicae

Contains the single family Porosporidae, with three genera and about 37 known species worldwide. Members have a two host life cycle, one a crustacean and the other a mollusc. Genera: Porospora, Nematopsis and Pachyporospora.

Gregarinicae

About seven families, 45 genera and 561 species known worldwide.

Family: Cephaloidophoridae

Three genera and about 70 species worldwide. Mainly intestinal parasites of crustaceans, particularly decapods, amphipods and cirripedes (barnacles). Genera: Cephaloidophora, Caridohabitans and Rotundula. 

Family: Cephalolobidae

Two genera and five known species worldwide. Mainly intestinal parasites of Crustacea. Genera: Cephalobus and Callynthrochlamys.

Family: Uradiophoridae

Five genera and 21 known species worldwide. Mainly intestinal parasites of Crustacea. Genera: Uradiophora, Heliospora, Pyxinioides, Nematoides and Bifilida.

Family: Gregarinidae

In total there are 14 genera and about 352 known species worldwide. Mainly intestinal parasites of insects. Genera: Gregarina, Clitellocephalus, Gymnospora, Triseptata, Gamocystis, Anisolobus, Anisoloboides, Garnhamia, Torogregarina, Faucispora, Spinispora, Bolivia, Cirrigregarina, Molluskocystis.

Family: Metameridae

Four genera and five known species worldwide. Parasites of annelids. Genera: Metamera (in leeches), Gopaliella, Deuteromera (in polychaetes) and Cognettiella (in polychaetes).

Family: Didymophyidae

Didymophyes is the sole genus, with 41 known species. Parasites of beetles (Coleoptera).

Family: Hirmocystidae

A total of 16 genera and 69 known species worldwide. Genera: Hirmocystis (in insects), Neohirmocystis, Hyalospora, Tettigonospora, Dumbbellicephalus, Euspora, Tintinospora, Arachnocystis (in arachnids), Acanthogregarina, Protomagalhaensia, Eliptocystis, Pintospora, Endomycola, Retractocephalus, Liposcelisus, Quadruhyalodiscus

Stenophoricae

Worldwide there are 14 families, about 103 genera and about 568 known species.

Family: Stenophoridae

There are three genera and 93 known species worldwide. All are intestinal parasites of millipedes. Genera: Stenophora, Fonsecaia and Hyalosporina.

Family: Leidyanidae

One genus (Leidyana) with 29 named species worldwide

Family: Cnemidosporidae

One genus (Cnemidospora) with four named species. Intestinal parasites of millipedes.

Family: Monoductidae

Three genera and 19 species worldwide. Primarily intestinal parasites of millipedes. Genera:  Monoductus, Stenoductus and Phleobum.

Family: Sphaerocystidae

Four genera and 12 named species worldwide. Mainly intestinal parasites of insects. Genera: Sphaerocystis, Schneideria, Paraschneideria and Neoschneideria.

Family: Trichorhynchidae

One genus (Trichorhynchus) with two species. Intestinal parasites of centipedes (Chilopoda).

Family: Dactylophoridae

Eight genera and 29 named species worldwide. Intestinal parasites of centipedes (Chilopoda). Genera: Dactylophorus, Echinomera, Grebnickiella, Rhopalonia, Acutispora, Seticephalus, Dendrorhynchus and Mecistophora.

Family: Amphiplatysporidae

One genus and one species.

Family: Stylocephalidae

Fifteen genera and 91 named species worldwide. Intestinal parasites of insects. Genera: Stylocephalus, Stylocephaloides, Cystocephalus, Bulbocephalus, Xiphocephalus, Lophocephalus, Lophocephaloides, Sphaerorhynchus, Oocephalus, Campanacephalus, Clavicephalus, Cystocephaloides, Orbocephalus, Lepismatophila and Colepismatophila.

Family: Actinocephalidae

Three subfamilies, 61 genera and 283 named species worldwide. Intestinal parasites of arthropods and chordates.

Subfamily: Actinocephalinae

Worldwide there are 38 genera and 187 named species. Genera: Actinocephalus (in insects), Caulocephalus (in beetles), Cornimeritus, Umbracephalus, Urnaepimeritus, Asterophora (in arthropods), Pileocephalus, Gemmicephalus, Pilidiophora, Geneiorhynchus (in dragonfly larvae), Acanthoepimeritus, Phialoides (in beetle larvae), Legeria (in beetle larvae), Pixinia (in beetles), Discorhynchus (in insect larvae), Steinina (in insects), Bothriopsides, Pomania, Stictospora (in insects), Coleorhynchus (in insects), Amphoroides (in millipedes), Stylocystis (in insects), Sciadiophora (in harvestmen [Opiliones]), Anthorhynchus, Agrippina (in flea larvae), Globulocephalus (in trichopteran larvae), Alaspora (in beetles), Amphorocephalus (in centipedes [Chilopoda]), Tricystis (in chaetognaths), Thalicola (in salps), Epicavus (in insects), Gryllotalpia (in insects), Chilogregarina (in centipedes [Chilopoda]), Crucocephalus, Harendraia, and Levinea (in Odonata).

Subfamily: Acanthosporinae

Twenty genera and 75 named species worldwide. Intestinal parasites of carnivorous insects (mainly aquatic insects), centipedes (Chilopoda) and harvestmen (Opiliones). Genera: Acanthospora (in insects), Grenoblia, Corycella, Ancyrophora, Rhizionella, Cometoides (in insects), Prismatospora, Nubenocephalus, Tetraedrospora (in fungus gnats [Mycetophilidae]), Ramicephalus, Coronoepimeritus, Dinematospora, Doliospora (in harvestmen [Opiliones]), Acanthosporidium, Cosmetophilus (in Opiliones), Contospora (in arthropods), Tetractinospora, Echinoocysta, Mukundaella (in insects), Tetrameridionospinospora,

Subfamily: Menosporinae

Worldwide there are five genera and 24 named species. Intestinal parasites of arthropods. Genera: Menospora (in insects), Hoplorhynchus, Odonaticola, Domadracunculus and Steganorhynchus.

Family: Brustiophoridae

One species in the genus Brustiophora, an intestinal parasite of a beetle.

Family: Acutidae

Two genera (Acuta and Apigregarina), each with a single named species. Intestinal parasites of honeybees.

Family: Monoicidae

One species in the genus Monoica, intestinal parasite of honeybees.

Fusionicae

A single species in the family Fusionidae and the genus Fusiona (intestinal parasite of insects).

Neogregarinorida

Family: Gigaductidae

One genus: Gigaductus.

Family: Caulleryellidae

Genera: Caulleryella and Tipulocystis.

Family: Ophryocystidae

One genus: Ophryocystis.

Family: Syncystidae

One genus: Syncystis.

Family: Schizocystidae

Genera: Schizocystis, Machadoella and Lymphotropha.

Family: Lipotrophidae

Genera: Lipocystis, Mattesia, Menzbieria, Farinocystis and Lipotropha