Order Pleurostomatida Schewiakoff, 1896
Oral area flattened along ventral margin of laterally comporessed body, surrounded by toxicysts; rhabdos made of three microtubular components: transverse ribbons originating from the oral dikinetids and in suborder Litonotina also from somatic monokinetids, nematodesmal bundles originating exclusively from oral dikinetids, and bulge microtubules; somatic ciliature with distinct left-right differetiation, including dorsal brush and, in some genera, one or two dorsolateral kineties; free-living and parasitic on other ciliates (mainly peritrichs), often large, lengthy voracious carnivores; widely distributed in frsehwater, marine, and interstitial habitats.
Type; Amphileptina Jankowski, 1967
Suborder Amphileptina Jankowski, 1967
Cytostome surrounded by a right and a left perioral kinety composed of dikinetids; right somatic ciliature with spica.
Type; Amphileptidae Butschli, 1889
Remarks; This suborder is monotypic, i.e. icludes only the family Amphileptidae Butschli with the characteristics given for the suborder. The genera Amphileptus (Ehrenberg 1830, Foissner 1984; type by virtual tautonymy), Opisthodon (Foissner 1984, Stein 1859) and Pseudoamphileptus (Foissner 1983) belong to this family. Hemiophrys (Wrzesniowski 1870) is a junior synonym of Amphileptus (Foissner 1984). Amphleptus carchesii Stein very likely needs a separate genus, because it has a heavily ciliated groove which secretes a loop-like structure anchoring the ciliate to the prey (Foissner et al. 1995). However, the separation should await a detailed study of its infraciliature.
Suborder Litonotina Foissner & Foissner, 1988
Cytostome surrounded by a right and left perioral kinety composed of dikinetid, right kinety accompanied by (oralized ?) somatic monokinetids forming a distinct 3rd perioral kinety whose transverse microtubular ribbons contribute to the rhados; right lateral ciliature with or without dorsolateral kineties, ciliary rows successively shortend along perioral and dorsolateral kineties.
Type; Litonotidae Kent, 1882
Remarks; This suborder includes the families Litonotidae Kent and Loxophyllidae n. fam., differing mainly by the absence/presence of right lateral dorsolateral kineties.
Family Litonotidae Kent, 1882: Litonotina without right dorsolateral kineties.
Type; Litonotus Wrzesniowski, 1870
Remarks; This family includes Litonotus (Foissner 1984, Wrzesniowski 1870), Acineria (Augustin et al. 1987, Dujardin 1841) and possibly, Heminotus (Kahl 1933) whose infraciliature has been not yet described.
Family Loxophyllidae n. fam.: Litonotina with dorsolateral kineties.
Type; Loxophyllum Dujardin, 1841
Remarks; Jankowski also mentioned a new family "Loxophyllidae" without, however, providing any characterization or type genus (Jankowski, 1975. A conspectus of the new system of subphylum Ciliophora Doflein, 1901. Abstract. In: Balashov, U.S. (ed.), Account of Scientific Sessions on Results of Scientific Work, Year 1974: Abstracts of Reports, Akad. Nauk. SSSR, Zool. Inst. Leningrad. Pp. 26-27 [in Russian]). Thus, the name is illegitimate, i.e. not in accordance with the rules of nomenclature. According to Grain (1993), Dujardin (1841) also founded a family Loxophyllidae. However, this is not confirmed by an inspection of the original literature. Dujardin (1841) included Loxophyllum and other pleurostomes in his new family Parameciidae. The family includes two genera, viz. Loxophyllum (Dujardin 1841, Foissner et al. 1995) and Siroloxophyllum n. g. Loxophyllum was formerly (Foissner and Foissner 1988) assigned to the Amphileptina because the data available suggested that it lacks perioral kinety 3. This was disproved by a reinvestigation (Foissner et al. 1995). Very likely, some of the many marine and interstitial Loxophyllum species are not congeneric. Unfortunately, their infraciliature is not known and any separation would be premature.