Cap 17

genera that have been sequenced 
do not form a strong monophyletic grouping 
(Chen & Song, 2001). We conservatively maintain 
this subclass until sequence data from additional 
genes provide evidence that the class should be 
subdivided. 
 Order Kiitrichida Nozawa, 1941 
 (syn. Protohypotrichina p.p .) 
 Size, medium; shape, small, rounded-elliptical 
in outline; frontoventral cirri, relatively small 
polykinetids, uniform in size, in 7–10 curving files
along right side of ventral surface ; oral region, 
broad area, on right; adoral zone of polykinetids 
bordering left margin of body and extending from 
near posterior end to near anterior end; paroral, bor-
dering almost entire length of right margin of oral 
region; macronucleus, ovoid; micronucleus, present;
contractile vacuole, absent; cytoproct (?); feeding 
on smaller protists; in marine habitats; one family. 
 Family KIITRICHIDAE Nozawa, 1941 
 With characteristics of order; three genera. 
 – Caryotricha Kahl, 1932 
 – Kiitricha Nozawa, 1941 
 – Musajevella Alekperov, 1984 
 Order Euplotida Small & Lynn, 1985 
 Size, small to medium; shape, ovoid to rectangu-
lar; free-swimming; frontoventral cirri, sporadically 
scattered over ventral surface, but never forming 
more than one conspicuous file on ventral surface, 
except in Gastrocirrhidae ; oral structures, as for 
subclass; during cell division, only the ventral 
somatic infraciliature is replaced while replica-
tion of the dorsal ciliature typically occurs within 
an equatorial band and within the parental kine-
ties (i.e., intrakinetally) ; caudal cirri, when present, 
derived from dorsal kinety anlagen; two suborders. 
 Suborder Discocephalina Wicklow, 1982 
 Size, small to medium; shape, elongate ovoid 
with anterior “head-like” part bearing oral region 
made distinct from main body by more or less obvi-
ous neck-like constriction ; free-swimming, but quite 
thigmotactic; right marginal cirri usually present, but 
not on Discocephalus ; file of left marginal cirri typi-
cally divided into anterior and posterior- lateral 
17.3 The Ciliate Taxa to Genus 349
parts ; transverse cirri, conspicuous with well-devel-
oped microtubular rootlets; caudal cirri, present; oral 
structures, as for subclass; macronucleus, often in 
many fragments; micronucleus, present; contractile 
vacuole, absent; cytoproct (?); feeding on microalgae 
and smaller protists; in marine habitats, especially 
sands; one family. 
NOTE : The Family Erionellidae was placed in 
this suborder by Lynn and Small (2002). However, 
its sole genus Erionella Jankowski, 1978 is likely a 
synonym of Holosticha (Aescht, 2001). 
 Family DISCOCEPHALIDAE Jankowski, 1979 
 (syns. Discocephalinae , Discocephaloidea , Margi-
notrichinae ) 
 With characteristics of the suborder; three genera. 
NOTE : Psammocephalus Wicklow, 1982 has 
been included in this family. Lin, Song, and 
Warren (2004) view it as a junior synonym of 
Prodiscocephalus Jankowski, 1979. 
 – Discocephalus Ehrenberg in Hemprich & 
Ehrenberg, 1831 
 – Marginotricha Jankowski, 1978 
 – Prodiscocephalus Jankowski, 1979 
 Suborder Euplotina Jankowski, 1979 
 (syn. Euplotia , Euplotiidea , Gastrocirrhida p.p ., 
 Uronychiida p.p .) 
 Size, small to medium; shape, ovoid to ovorec-
tangular; free-swimming; right marginal cirri, 
absent ; left marginal cirri, when present, not 
as two distinct groups ; oral structures, as for 
subclass; contractile vacuole, typically in right 
posterior of body ; in marine, freshwater, and 
terrestrial habitats; five families. 
 Family ASPIDISCIDAE Ehrenberg, 1830 
 (syn. Aspidiscina , Aspidiscoidea , Euplotaspinae , 
 Paraeuplotidae ) 
 Size, small; shape, flattened and disc-like; free-
swimming, highly thigmotactic; dorsal surface 
may be ridged; no left marginal cirri ; transverse 
cirri, conspicuous; caudal cirri, absent; reduced 
number of oral membranelles, located centrally 
and inconspicuously on ventral surface ; paroral, 
reduced or absent; macronucleus usually C-shaped; 
micronucleus, present; contractile vacuole, present; 
cytoproct (?); feeding on bacteria, microalgae, and 
smaller protists; in marine and freshwater habitats, 
widely distributed, often benthic but including com-
mensals in the echinoid gut and ascidian branchial 
cavity; two genera and one genus incertae sedis . 
 – Aspidisca Ehrenberg, 1830 
 – Euplotaspis Chatton & Séguéla, 1936 
Incertae sedis in Family Aspidiscidae 
 – Paraeuplotes Wichterman, 1942 
 Family CERTESIIDAE Borror & Hill, 1995 
 (syn. Certesiina , Certesiinae ) 
 Size, small; shape, broadly ovoid; free-swimming; 
unique condylopallium in anterior end of cell; 
left marginal cirri more than three ; transverse 
cirri, large, well-developed; caudal cirri, absent; 
adoral zone of polykinetids, well-developed and 
continuous; paroral polykinetid conspicuous, exten-
ding along two thirds length of the oral cavity; 
macronucleus, ellipsoid, two to four in number; 
micronuclei, several; contractile vacuole, present; 
cytoproct (?); feeding on diatoms and other smaller 
protists; in marine habitats; one genus. 
 – Certesia Fabre-Domergue, 1885 
 Family EUPLOTIDAE Ehrenberg, 1838 
 (syn. Euplotiidea , Euplotidiidae , Euplotidiinae , 
 Euplotina , Euplotinae , Ploesconiidae ) 
 Size, small to medium; shape, ovoid, ventrally-
flattened; body, rigid; free-swimming; extrusomes 
as small vesicles (i.e., ampules) associated with dorsal 
bristle dikinetids; frontoventral and transverse cirri, 
dispersed in conspicuous groups; left marginal 
cirri, reduced typically to fewer than three ; 
caudal cirri, ventral; ventrally-oriented oral cavity 
with distinct, contiguous, adoral zone of oral 
polykinetids forming a “collar” and “lapel” ; 
paroral as polykinetid on right of oral area 
accompanied by single endoral file of kineto-
somes ; macronucleus, more or less C-shaped; 
micronucleus, present; contractile vacuole, present; 
cytoproct (?); feeding on bacteria, microalgae, and 
smaller protists; in marine, freshwater, and terres-
trial habitats, widely distributed but predominantly 
marine, with one Euplotes species found in the 
intestines of sea urchins; four genera. 
350 17. The Ciliate Taxa Including Families and Genera
 – Euplotes Ehrenberg in Hemprich & Ehrenberg, 
1831
 – Euplotoides Borror & Hill, 1995 
 – Euplotopsis Borror & Hill, 1995 
 – Moneuplotes Jankowski, 1978 
 Family GASTROCIRRHIDAE Fauré-Fremiet, 1961 
 (syns. Cytharoidinae , Gastrocirrhida , Gastro-
cirrhina , Gastrocirrhinae , Gastrocirrhoidea ) 
 Size, medium; shape, conoid, nearly round in 
cross-section; free-swimming; frontoventral cirri 
apparently in two files; left marginal cirri, 
inconspicuous or absent ; transverse cirri, many, 
conspicuous, in U-shape; expansive, anteriorly-
opened oral cavity with anterior end of body 
remarkably truncate ; macronucleus, ellipsoid, 
typically in two fragments; micronucleus, present; 
contractile vacuole, absent; cytoproct (?); feed-
ing on bacteria, microalgae, and smaller protists; 
in marine habitats, either planktonic or psam-
mophilic; three genera. 
NOTE : Paraeuplotidium Lei, Choi, and Xu, 2002 
is considered a junior synonym of Euplotidium
since the single left marginal cirrus proposed by 
Lei, Choi, and Xu (2002) as a character of generic 
distinctiveness must be corroborated first by gene 
sequence data to confirm its significance. 
 – Cytharoides Tuffrau, 1975 
 – Euplotidium Noland, 1937 
 – Gastrocirrhus Lepsi, 1928 
 Family URONYCHIIDAE Jankowski, 1975 
 (syns. Diophryidae , Swedmarkiidae , Uronychiida ) 
 Size, small to medium; shape, blunt ovoid, nearly 
circular in cross-section; free-swimming; cirri, gen-
erally conspicuous with frontoventral cirri reduced to 
groupings on right side; transverse cirri, well-devel-
oped; right caudal cirri, dorsal, well-developed ; 
left marginal cirri, may be conspicuous; oral region, 
expansive, with