Belongs within: Ciliophora.
Contains: Apostomatia, Astomatia, Peniculia, Scuticociliatia, Tetrahymenida, Mobilida, Vorticellidae, Epistylididae, Operculariidae, Vaginicolidae.
The Oligohymenophorea are a group of ciliates often possessing a distinct oral apparatus in a ventral oral cavity or infundibulum (Adl et al. 2019).
Characters (Adl et al. 2019): Oral apparatus often with distinct right paroral kinety and typically three left oral polykinetids, residing in ventral oral cavity or deeper infundibulum; somatic monokinetids typically with anteriorly directed overlapping kinetodesmal fibrils, divergent postciliary ribbons, and radial transverse ribbons.
<==Oligohymenophorea [Epiplasmata, Oligohymenophora]
| i. s.: ApostomatiaAS12
|--HymenostomataD86
| | i. s.: Lembus veliferD86, G84
| | Tanystomium gracile (Powers 1933) [=Cryptochilidium gracile, Biggaria gracilis]BK77
| | Andreula antedonis (André 1910) [=Conchophthirus antedonis]BK77
| | Madsenia Kahl 1934BK77
| | `--M. indomita (Holger Madsen 1931) [=Entodiscus indomitus]BK77
| |--AstomatiaC74
| `--+--+--PeniculiaL03
| | `--ScuticociliatiaL03
| `--Hymenostomatia [Hymenostomatida]AS12
| |--TetrahymenidaL03
| `--Ophryoglenida [Ophryoglenina]AB19
| |--Ichthyophthirius Fouquet 1876 [Ichthyophthiriidae]LS02
| | `--I. multifiliisFS-K03
| `--Ophryoglena [Ophryoglenidae]AB19
| |--O. catenulaL03
| `--O. singularisLS02
`--Peritrichia [Peritricha, Peritrichida]AS12
|--MobilidaAB19
`--Sessilida [Sessilina]AB19
|--VorticellidaeL03
|--EpistylididaeAB19
|--OperculariidaeAB19
|--VaginicolidaeAB19
|--Ellobiophrya Chatton & Lwoff 1923 [Ellobiophryidae]LS02
| `--E. donacisLS02
|--Rovinjella Matthes 1972 [Rovinjellidae]LS02
| `--R. sphaeromaeLS02
|--Termitophrya Noirot-Timothée 1959 [Termitophryidae]LS02
| `--T. africanaLS02
|--Usconophrys Jankowski 1985 [Usconophryidae]LS02
| `--U. apertaLS02
|--AstylozoidaeAB19
| |--Astylozoon Engelmann 1862LS02
| | `--A. enriquesiLS02
| `--Hastatella Erlanger 1890LS02
| `--H. radiansLS02
|--OpisthonectidaeLS02
| |--Opisthonecta Fauré-Fremiet 1906LS02
| | |--O. bivacuolataLS02
| | `--O. henneguyiL03
| `--Telotrochidium Kent 1881LS02
| |--T. cylindricumLS02
| `--T. johanninaeLS02
|--ZoothamniidaeAB19
| |--HaplocaulusAB19
| `--Zoothamnium Bory de St. Vincent 1826LS02
| |--Z. alternansC79
| |--Z. arbusculaC79
| |--Z. parasitaD01
| |--Z. simplexLS02
| `--Z. vermicola [=Myoschiston vermicola]BK77
|--ScyphidiidaeAB19
| |--Paravorticella Kahl 1933LS02
| | `--P. terebellaeLS02
| |--Ambiphrya Raabe 1952LS02
| | `--A. miriLS02
| `--Scyphidia Dujardin 1841LS02
| |--S. amphibiarumLS02
| |--S. dentataLS02
| `--S. haemopisLS02
`--LagenophryidaeAB19
|--Operculigera Kane 1969LS02
| `--O. asymmetricaLS02
|--Paralagenophrys Clamp 1987LS02
| `--P. singularisLS02
|--Clistolagenophrys Clamp 1991LS02
| `--C. primitivaLS02
|--Setonophrys Jankowski 1986LS02
| `--S. communisLS02
|--Stylohedra Kellicott 1884LS02
| `--S. lenticulaLS02
`--Lagenophrys Stein 1851LS02
|--L. ampullaLS02
|--L. labiataLS02
|--L. monolistraeS86
`--L. vaginicolaD01