arc-like file that parallels the anterior left serial oral polyki- netids and a frontoventral cirral zig-zag with 362 17. The Ciliate Taxa Including Families and Genera 1–6 files to the right of left marginal cirral file and also with several cirral files to the left of the right marginal cirri; multiple “marginal files” derive from unique anlagen during morpho- genesis ; transverse cirri, present or absent; caudal cirri, absent; dorsal somatic ciliature as several files of bristle dikinetids; oral ciliature as for order with paroral and endoral; macronucleus, ellipsoid, multiple; micronucleus, present; contractile vacu- ole, present; cytoproct, likely present; feeding on bacteria, algae, smaller protists, including testate amoebae and ciliates; in freshwater and terrestrial habitats; three genera. – Hemicycliostyla Stokes, 1886 – Pseudourostyla Borror, 1972 – Trichotaxis Stokes, 1891 Family UROSTYLIDAE Bütschli, 1889 (syns. Bakuellidae , Bakuellinae , Erionellidae , Holostichidae , Holostichina , Holostichinae , Holostichoidea , Psammomitrinae Pseudoam- phisiellidae , Urostylinae , Urostyloidea ) Size, small to large; shape, elongate ovoid with some tailed forms; free-swimming; somatic ven- tral ciliature with several frontal cirri some- what larger than other frontoventral cirri, and with frontoventral cirri as a single zig-zag file of paired cirri or a series of shorter files off- set at their anterior and posterior ends (e.g., Bakuella, Eschaneustyla ) and typically not with additional “marginal files” on both sides of this zig-zag (cf. Pseudourostylidae) ; transverse cirri, may be numerous; caudal cirri, present or absent; dorsal somatic ciliature as three to many files of bristle dikinetids; oral ciliature as for order with paroral and endoral; during division morpho- genesis, frontoventral cirri differentiate from a longitudinal field of more than five oblique cili- ary streaks; macronucleus, ellipsoid, two to many nodules; micronucleus, present; contractile vacu- ole, present; cytoproct, likely present; feeding on bacteria, algae, and smaller protists, including ciliates; in marine, freshwater, and terrestrial habitats; 24 genera. – Afrothrix Foissner, 1999 – Anteholosticha Berger, 2003 * – Australothrix Blatterer & Foissner, 1988 – Bakuella Agamaliev & Alekperov, 1976 – Biholosticha Berger, 2003 * – Birojimia Berger & Foissner, 1989 – Caudiholosticha Berger, 2003 * – Diaxonella Jankowski, 1979 – Holosticha Wrzesniowski, 1877 – Holostichides Foissner, 1987 – Metabakuella Alekperov, 1989 – Metaurostylopsis Song, Petz, & Warren, 2001 * – Notocephalus Petz, Song, & Wilbert, 1995 – Parabirojimia Hu, Song, & Warren, 2002 * – Paragastrostyla Hemberger, 1985 – Paramitrella Jankowski, 1978 – Paruroleptus Wenzel, 1953 (subj. syn. Uroleptus ) – Periholosticha Hemberger, 1985 – Perisincirra Jankowski, 1978 – Psammomitra Borror, 1972 (subj. syn. Uroleptus ) – Pseudoamphisiella Song, 1996 – Pseudobakuella Alekperov, 1992 – Tunicothrix Xu, Lei & Choi, 2006 * – Uroleptus Ehrenberg, 1831 – Urostyla Ehrenberg, 1830 Incertae sedis in Subclass Stichotrichia – Erniella Foissner, 1987 – Gastrosticha Kahl, 1932 [nomen dubium] – Saudithrix Berger, Al-Rasheid, & Foissner, 2006 * – Stenotricha Jankowski, 1978 – Uncinata Bullington, 1940 Subclass Oligotrichia Bütschli, 1887/1889 (syns. Oligotricha , Oligotrichorida ) Size, small to large, shape, typically rounded or gently pointed posteriorly, sometimes tailed; free-swimming; a perilemma present in many spe- cies; internal polysaccharide plates in some spe- cies; somatic kineties, reduced in number and variable in pattern, forming girdles and spirals, typically derived from an “equatorial” girdle kinety and a “ventral” kinety of dikinetids that originates near the posterior pole ; extrusomes often prominent rod-like “trichites”; oral region on anterior half with oral polykinetids extensive and conspicuous in two sections – a “collar” out on the body surface encircling anterior pole of organism and a “lapel” inside the oral cavity proper ; paroral, a single file of kinetosomes (i.e., monostichomonad); stomatogenesis, apokinetal, often in a below-surface pouch; division morpho- 17.3 The Ciliate Taxa to Genus 363 genesis, enantiotropic-like; macronucleus, globular to ellipsoid to band-like, often multiple; micronu- cleus, present; contractile vacuole, at least present in freshwater forms; cytoproct, possibly absent; feeding on bacteria, microalgae, and smaller pro- tists, but mixotrophic species common; in marine and freshwater habitats, free-living as plankton but several species endocommensals in echinoids; one order. NOTE : Our classification reflects the molecu- lar genetic analyses that suggest the halteriids , classically considered oligotrichs , arose within the stichotrichs while the strombidiids are a sepa- rate lineage probably related to the choreotrichs (Snoeyenbos-West, Salcedo, McManus, & Katz, 2002; Strüder-Kypke & Lynn, 2003). Order Strombidiida Petz & Foissner, 1992 (syn. Strombidiina ) With characterististics of the class; two families. Family STROMBIDIIDAE Fauré-Fremiet, 1970 (syns. Cyrtostrombidiidae , Pelagostrombidiidae ) With characteristics of the order; without an elongate and conspicuous contractile tail, but tail is often lost in fixed specimens (see Tontoniidae below); 17 genera. NOTE : We have listed all the names of strom- bidiid genera considered valid by Aescht (2001) and Agatha (2004). However, it is highly doubtful given recent research on the molecular evolution of strombidiids that all these genera represent mono- phyletic clades (e.g., see Agatha, Strüder-Kypke, Beran, & Lynn, 2005; Snoeyenbos-West et al., 2002; Strüder-Kypke & Lynn, 2003). – Buehringa Busch, 1921 (subj. syn. Strombidium ) – Cyrtostrombidium Lynn & Gilron, 1993 – Echinostrombidium Jankowski, 1978 – Laboea Lohmann, 1908 – Limnostrombidium Krainer, 1995 – Lissostrombidium Jankowski, 1978 – Metastrombidium Fauré-Fremiet, 1924 – Novistrombidium Song & Bradbury, 1998 – Omegastrombidium Agatha, 2004 * – Parallelostrombidium Agatha, 2004 * – Pelagostrombidium Krainer, 1991 – Peristrombidium Jankowski, 1978 – Pseudostrombidium Horváth, 1933 – Seravinella Alekperov & Mamajeva, 1992 – Spirostrombidium Jankowski, 1978 – Strombidium Claparède & Lachmann, 1859 – Thigmostrombidium Jankowski, 1978 Family TONTONIIDAE Agatha, 2004 With characteristics of the order; with elongate and conspicuous contractile tail, but tail is often lost in fixed specimens ; four genera. – Paratontonia Jankowski, 1978 (subj. syn. Tontonia ) – Pseudotontonia Agatha, 2004 * – Spirotontonia Agatha, 2004 * – Tontonia Fauré-Fremiet, 1914 Class ARMOPHOREA Lynn, 2004 Size, small to large; shape, varied from top- shaped with spines to laterally flattened and leaf-like; alveoli, conspicuous to absent; somatic dikinetids with both kinetosomes bearing cilia, typically distributed in kineties covering entire body, but in smaller forms ciliature reduced to tufts or cirri; hydrogenosomes, with remnant genome retained in some forms, replacing mitochondria; oral polykinetids on left side of oral cavity, few and inconspicuous to many, forming an adoral zone; stomatogenesis, typi- cally pleurokinetal; macronucleus, single, large, and ellipsoid to elongate, but sometimes multi- ple; conjugation, typically temporary, but may be total in some armophorids; contractile vacu- ole, present, sometimes with collecting canals; cytoproct, may be present; bacterivorous, but also with endosymbiotic methanogens; in marine, freshwater, and rarely terrestrial anaerobic habi- tats (i.e. polysaprobic), typically in sediments and the intestinal