[ref. ID; 4746 (Wilhelm Foissner and Ilse Foissner, 1988)]

Class Litostomatea Small & Lynn, 1981
Subclass I. Haptoria Corliss, 1974
Order I. Haptorida Corliss, 1974
Suborder (1) Enchelyina nov. subord.
Suborder (2) Acropisthiina nov. subord.
Suborder (3) Dileptina Jankowski, 1978
Order II. Spathidiida nov. ord.
Suborder (1) Spathidiina Jankowski, 1980
Suborder (2) Belonophryina Jankowski, 1980
Suborder (3) Didiniina Jankowski, 1978
Order III. Pleurostomatida Schewiakoff, 1896
Suborder (1) Amphiloeptina Jankowski, 1967
Suborder (2) Litonotina nov. subord.
Order IV. Pseudoholophryida nov. ord.
Suborder (1) Pseudoholophryina nov. ord.
Suborder (2) Helicoprorodontina nov. subord.
Order V. Archistomatida Puytorac et al., 1974
Order VI. Cyclotrichina Jankowski, 1980

Subclass II. Trichostomatia Butschli, 1889


Subclass Haptoria Corliss, 1974
Usually uniform holotrichous somatic ciliation; somatic kineties often longitudinally, rarely right-spiralling; somatic monokinetids with short kinetodesmal fibrils, 2 tangential transverse ribbons, and moderately overlapping, weakly convergent postciliary ribbons; cytostome usually apical, rarely subapical or antapical, round, oval or slit-like, not permanently open; oral kinetids are usually dikinetids whose transverse ribbons extend from the anterior kinetosomes to support the cytopharynx; in groups lacking oral dikinetids, the rhabdos is built from oralized somatic kinetids which have nematodesmal bundles and long transverse ribbons; bulge (cone) microtubules, tela corticalis, and toxicysts usually present; dorsal brush common, within somatic kineties, thus longitudinally oriented, consists of paired clavate cilia; silverline system fine-meshed, between brush kineties often platyophryid or colpodid; stomatogenesis telokinetal; most are free-living, rapacious carnivores, some are parasites or endocommensals.
Remarks; The characterization of the kinetids is based on Lynn (1981, 1985) and Small & Lynn (1981, 1985). The second tangential transverse ribbon of the somatic monokinetids has probably often been overlooked; it is, however, possible that it really is absent in some groups. The Haptoria are divided into six orders, 2 of which are new. Small and Lynn (1985) established the new haptorid order Pharyngophorida which is characterized by a permanent cytopharynx and includes the families Actinobolinidae, Helicoprorodontidae, and Tracheliidae. Several problems exist with this suggestion. Firstly, there already exists the order Dileptida, which includes at least the Tracheliidae, and the suborder Belonophryina, which covers the Actinobolinidae (Jankowski 1978, 1980). Secondly, one must ask, whether there really are Haptorids which do not have a "permanent cytopharynx lined by the transverse microtubular ribbons of the oral dikinetids". As far as we can see from our data and from the literature this is not the case. The central area of the cytostome is always more (Actinobolina, Enchelydium) or less (Helicoprorodon, Spathidium) indented, lined by the more or less pronounced transverse ribbons of the oral kinetids, and surrounded or filled with phagoplasm. There exist certainly some variations in this pattern, but this seem to be due to the different shape and height of the oral bulge (cone) which are, however, often very different even within a single genus (Foissner 1984). In addition, the families included in the Pharygophorida seem to be a rather random assemblage. Are, for instance, the Tracheliidae really nearer to the Helicoprorodontidae than no the Enchelyina or Spathidiida? Altogether, we see no advantage of this order.

Order Haptorida Corliss, 1974
Cytostome apical or subapical, round, oval or slit-like; rhabdos made of three microtubular components: transverse ribbons originating from the nonciliated oralized somatic monokinetids or oral dikinetids, nematodesmal bundles originating from the same source and/or from ciliated or nonciliated oralized somatic monokinetids, and bulge microtubules; somatic ciliation uniform; dorsal brush composed of two or more kineties; toxicysts localized, typically in or near oral area; free-living, suborder Dileptina with conspicuous proboscis.
Type; Enchelyina nov. subord.
Remarks; This characterization is based on the studies of Corliss (1979), Foissner and Foissner (1985) and the present investigation. The order Haptorida is best distinguished from all other haptorian taxa by the occurrence of oralized somatic monokinetids bearing nematodesmal bundles.

Suborder Enchelyina nov. subord. (ref. ID; 4746 original paper)
Cytostome apical, round or oval; nematodesmal bundles originate exclusively from nonciliated oralized somatic monokinetids which bear also long transverse ribbons; dorsal brush consists of three kineties.
Type; Enchelyidae Ehrenberg, 1838
Remarks; This new suborder is based on the investigations Foissner (1984) and Foissner and Foissner (1985) which show that Enchelys and Enchelydium lack oral dikinetids. These 2 genera, and probably Papillorhabdos Foissner, 1984, may be united in the family Enchelyidae Ehrenberg, 1838. Corliss (1979) assigns to this family a lot of other, mostly poorly described genera. Some of them (e.g. Enchelyodon, Trachelophyllum, Lacrymaria) are now considered to belong to other families.

Suborder Acropisthiina nov. subord. (ref. ID; 4746 original paper)
Cytostome apical, round or oval; nematodesmal bundles originate from typical haptorid oral dikinetids and from ciliated oralized somatic monokinetids. Dorsal brush consists of two to three kineties.
Type; Acropisthiidae nov. fam.
Remarks; This new suborder is based on the present investigations and those of Bohatier and Detcheva (1973) and Foissner (1984) which show that Acropisthium, Fuscheria, and Actinorhabdos (separated from Fuscheria by its graver-like toxicysts) have the same type of oral infraciliature. Thus, these 3 genera are united in the new family Acropisthiidae nov. fam. (with the same characterization as the suborder; Type: Acropisthium Perty, 1852).

Suborder Dileptina Jankowski, 1978
Oral area bipartited in a proboscis bearing ciliated oral dikinetids without nematodesmata and in a subapical cytostomal-cytopharyngeal complex with nonciliated oralized somatic monokinetids bearing nematodesmata; dorsal brush usually consists of more than 3 kineties.
Type; Tracheliidae Ehrenberg, 1838
Remarks; This special pattern is evident from the studies of Grain and Golinska (1969) and Golinska (1986) and shows the need of a separate suborder for the Tracheliidae. Jankowski (1980) even suggests a separate subclass for the Tracheliidae, the Rhynchostomata with the single order Dileptida. He gives, however, a very poor characterization of these taxa. We believe that at present the subordinal rank is more appropriate because the dorsal brush, the somatic infraciliature and the ecology of Dileptus and related genera are very near to many other members of the Haptorida (Foissner 1984; Dragesco and Dragesco-Kerneis 1986)

Order Spathidiida nov. ord. (ref. ID; 4746 original paper)
Cytostome apical, round or slit-like, in suborder Didiniina on top of cone-like proboscis; rhabdos made of three microtubular components: transverse ribbons originating from the nonciliated kinetosomes of the oral dikinetids, nematodesmal bundles originating exclusively from the same source, and bulge microtubules; somatic ciliation uniform or limited to dense bands which, however, rest within longitudinally running kineties composed of nonciliated kinetids; dorsal brush composed of 2 to many kineties; toxicysts localized, typically in or near oral area; free-living.
Type; Spathidiina Jankowski, 1980
Remarks; This new order is based mainly on the studies of Wessenberg and Antipa (1968); Bohatier (1970); Holt et al. (1973); Rodrigues de Santa Rosa and Didier (1975); Bohatier et al. (1978); Kuhlmann et al. (1980); Williams et al. (1981); Foissner (1984) and Lynn and Nicholls (1985). The oral structures show a rather great uniformity within this order. Thus, the more differentiated somatic kinetids and other cortical structures are used to distinguish suborders. (ref. ID; 4746)

Suborder Spathidiina Jankowski, 1980
Cytostome apical, round, oval or slit-like, in some genera covering the "ventral" body margin; somatic ciliation usually uniform.
Type; Spathidiidae Kahl in Doflein and Reichenow, 1929
Remarks; This suborder contains the families Spathidiidae Kahl in Doflein and Reichenow, 1929, Trachelophyllidae Kent, 1882, Lacrymariidae Fromentel, 1876, and Homalozoonidae Jankowski, 1980. Do the Homalozoonidae which have, like the Pleurostomatida, a rather distinct left-right differentiation of the somatic ciliation (Foissner 1984) need a separate order or suborder as proposed by Jankowski (1980)?.

Suborder Belonophryina Jankowski, 1980
Cytostome apical, round; somatic ciliation uniform; nonsuctorial tentacles widely distributed over body.
Type; Actinobolinidae Kahl, 1930
Remarks; This characterization is based mainly on the investigation of Actinobolina by Holt et al. (1973). This genus has some resemblance to Fuscheria because oral trikinetids (or oralized somatic monokinetids?) occur which bear 2 bundles of nematodesmata. The exact composition and shape of the brush are still unknown, but clavate cilia have been shown electron microscopy (Holt et al. 1973). Contains single family Actinobolinidae Kahl, 1930.

Suborder Didiniina Jankowski, 1978
Cytostome apical on conspicuous cone-like proboscis; somatic ciliation bipartited in one or more ciliated and nonciliated girdles which bear longitudinally arranged kineties with nonciliated kinetids.
Type; Didiniidae Poche, 1913
Remarks; The oral pattern of Monodinium bears some resembles to that of Helicoprorodon. There are, however, difference which suggest that this is an analogy. In Monodinium all somatic kineties bear 2 to 3 oral dikinetids causing a distinct "closed" circumoral kinety (Rodrigues de Santa Rosa and Didier 1975), whereas such kinetids are restricted to a few specialized kineties in Helicoprorodon which, thus has an "open" circumoral kinety (Raikov and Kovaleva 1980). Contains single family Didiniidae Poche, 1913.

Order Pleurostomatida Schewiakoff, 1896
Oral area flattened along ventral margin of laterally compressed body, surrounded by toxicysts; rhabdos made of three microtubular components: transverse ribbons originating from the oral dikinetids and in suborder Litonotina from somatic monokinetids too, nematodesmal bundles originating exclusively from the oral dikinetids, and bulge microtubules; somatic ciliature shows left-right differentiation; dorsal brush present; free-living and parasitic on other ciliates (especially peritrichs), often large, lengthy voracious carnivores, widely distributed and facultatively interstitial.
Type; Amphileptina Jankowski, 1967
Remarks; This characterization is based mainly on the studies of Bohatier and Njine (1973), Puytorac and Rodrigues de Santa Rosa (1975), and Corliss (1979). Small and Lynn (1985) give a wrong definition because the left oral kinety is never associated with somatic monokinetids. Although there is still some uncertainly about the exact composition of the oral structures of the Pleurotstomatida, a large distinction is obvious, which suggests that the order should be divided into 2 suborders.

Suborder Amphileptina Jankowski, 1967
Cytostome surrounded by a right and a left oral kinety composed of dikinetids; right somatic infraciliature with "spica".
Type; Amphileptidae Butschli, 1889
Remarks; To this suborder belong the genera Amphileptus, Pseudoamphileptus, Opisthodon, and Loxophyllum (see Puytorac and Rodrigues de Santa Rosa 1975; Foissner 1983, 1984) which are united in the family Amphileptidae Butschli, 1889. Loxophyllum probably deserves a family of its own.

Suborder Litonotina nov. subord.
Cytostome surrounded by a right and a left oral kinety composed of dikinetids, right oral kinety continuous with (oralized?) somatic monokinetids (arranged in a distinct "perioral kinety 3") whose transverse ribbons to the rhabdos; somatic kineties of the right side successively shortened along the cytostome.
Type; Litonotidae Kent, 1882
Remarks; To this suborder belong the genera Litonotus and Acineria (see Bohatier and Njine 1973; Foissner 1984; Augustin et al. 1987) which are united in the family Litonotidae Kent, 1882.

Order Pseudoholophryida nov. ord. (ref. ID; 4746 original paper)
Cytostome apical, round or oval; rhabdos made of the same microtubular components as in the Spathidiida; somatic ciliation uniform, but kineties more or less distinctly spirally arranged; dorsal brush absent or highly aberrant; toxicysts localized, typically in or near oral area; free-living.
Type; Pseudoholophryina nov. surord.
Remark; This characterization is based on the studies of Puytorac and Kattar (1969); Raikov and Kovaleva (1980), Berger et al. (1984) and Foissner (1984). Members of the Pseudoholophryina are known from light microscopical observations only. Thus, there is some uncertainty about their fine details. But oral dikinetids and transverse ribbons have been identified at least in Paraenchelys and Ovalorhabdos (Foissner 1984). The main character of this new order is the absence of a typical haptorian dorsal brush, a feature which is shared by the Archistomatida and Cyclotrichida. Thus, these 3 orders could be united in a separate subclass, if further studies can prove that this absence is a true homology which is, however, not very likely.

Suborder Pseudoholophryina nov. subord. (ref. ID; 4746 original paper)
Cytostome apical, round or oval; dorsal brush lacking or highly aberrant.
Type; Pseudoholophryidae Berger et al., 1984
Remarks; This new suborder contains the single family Pseudoholophryidae Berger et al., 1984, which includes 3 genera. Pseudoholophrya Berger et al., 1984 and Ovalorhabdos Foissner, 1984 lack a dorsal brush. The "brush" of Paraenchelys Foissner, 1983 covers a large field in the anterior area of the cell and consists of many short arced kineties whose kinetosomes are not clearly paired.

Suborder Helicoprorodontina nov. subord. (ref. ID; 4746 original paper)
Cytostome apical, round; oral dikinetids not arranged in a distinct circumoral kinety but at the top of some somatic kineties whose anterior ends spiral around the cytostome ("oralized somatic dikinetids"); exclusively in marine sands.
Type; Helicoprorodontidae Small & Lynn, 1985
Remarks; This characterization is based on the studies of Puytorac and Kattar (1969) and Raikov and Kovaleva (1980). The rhabdos of Helicoprorodon is very similar to that of the Spathidiina. The special kineties which spiral around the cytostome and bear the oral dikinetids are, however, such an extraordinary feature that a subordinal rank seems appropriate. No exact data are available concerning the dorsal brush and the arrangement of the somatic kineties. Contains the single family Helicoprorodontidae Small & Lynn, 1985 (the family is credited to these authors because Jankowski 1975 did not give a diagnosis).

Order Archistomatida Puytorac et al., 1974
Cytostome apical, round or oval; rhabdos made of 2 microtubular components: transverse ribbons and nematodesmal bundles originating from ciliated oralized somatic monokinetids; somatic ciliation uniform or limited to tufts and bands; toxicysts and haptorid dorsal brush absent; concrement vacuole present; exclusively endocommensals, principally in horses and camels.
Type; Buetschliidae Poche, 1913
Remarks; Characterization principally according to Corliss (1979) and Small and Lynn (1985). Single family Buetschliidae Poche, 1913. Many of the genera listed by Corliss (1979) in this family are now considered to belong to other subclasses (Jankowski 1980; Small and Lynn 1985). The rhabdos of the Archistomatida resembles that of the Enchelyina in the order Haptorida. It differs, however, by the absence of bulge microtubules and by the ciliated nematodesmata bearing oralized somatic monokinetids.

Order Cyclotrichida Jankowski, 1980
Cytostomal-cytopharyngeal structures apical or antapical, in some genera strongly reduced and probably functionless; rhabdos without nematodesmata and bulge microtubules, but probably with transverse ribbons; somatic ciliation limited to 2 cirri-like girdles; dorsal brush absent; toxicysts present; often with incomplete cryptomonad symbionts.
Type; Mesodiniidae Jankowski, 1980
Remarks; This characterization is based on the studies of Borror (1963); Taylor et al. (1971); Jankowski (1980); Grain et al. (1982) and Wilbert (1986). The absence of a dorsal brush and of nematodesmata (at least in Myrionecta rubra; see Taylor et al. 1971 and Grain et al. 1982) and the widely meshed silverline system in Askenasia (Foissner, unpubl.) suggest that this order probably belongs to another subclass. Details of the oral apparatus are, however, too poorly known to find a more meaningful affinity than that conventionally suggested. Contains single family Mesodiniidae Jankowski, 1980 (first named, but not diagnosed in Jankowski 1975).