<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

Aplanopsis, Apodachlya, Aquastella, Geolegnia, Leptomitus, Newbya, Pythiopsis, Protoachlya, Salisapilia, Saprolegnia, Thraustotheca.

●●●● Peronosporalean lineage Lara in Adl et al. 2019

Obligate biotrophs and facultative parasites. Oogamous sexual reproduction. Unable to synthesize sterols required for sexual reproduction. Characteristic periplasmic pattern of oogenesis. *Albugo*, *Bremia*, *Chlamydomyzium*, *Halophytophora*, *Hyaloperonospora*, *Lagenidium*, *Myzocytiopsis*, *Peronospora*, *Plasmopara*, *Pythium*, *Pseudoperonospora*, *Phytophthora*, *Phytopythium*, *Pustula*.

●●●● Pirsoniales Cavalier-Smith 1998, emend. 2006

Biciliate parasites of diatoms that differentiate into an intracellular feeding part (trophosome) and external generative part (auxosome). *Pirsonia*.

●●●● Actinophryidae Claus 1874, emend. Hartmann 1926

Axopodia emerging from amorphous centrosome near nuclei; axonemal microtubules in double interlocking coils; single central nucleus or several peripheral nuclei; tubular mitochondrial cristae; two types of extrusomes for prey-capture along axopodia; cysts covered with siliceous elements; autogamy reported within cysts; cell division with semi-open orthomitosis; cilia never formed; freshwater and marine. *Actinophrys*, *Actinosphaerium*.

●●●● Ochrophyta Cavalier-Smith 1986, emend. Cavalier-Smith & Chao 1996

Commonly with chloroplasts, endoplasmic reticulum surround plastids like a membrane; plastids commonly containing chlorophyll *c1*, and often *c2*.

●●●●● Chrysista Cavalier-Smith 1986

Unicellular, or filamentous or parenchymatous; ciliary supra-tz helix ancestrally; eyespot present or absent; transitional helix present or absent; chloroplast usually few in number and with girdle lamella; chloroplasts endoplasmic reticulum usually attached to the nuclear envelope.

*Incertae sedis* Chrysista: Environmental lineages MOCH-3, MOCH-5 Massana et al. 2014

Uncultured groups detected in molecular marine surveys amplifying directly 18S rDNA genes. These clades are mostly detected in the analysis of small size fractions (pico and nanoeukaryotes).

*Incertae sedis* Chrysista: Environmental lineages Synchromophyceae, Chrysomerophyceae, *Picophagus*, *Chrysowaernella*, *Aurearena*.

●●●●●● Chrysophyceae Pascher 1914

Predominately ciliated cells, but also capsoid, coccoid, filamentous and parenchymatous forms; swimming cells bicipitated—one anteriorly directed and one laterally directed; tripartite mastigonemes with short and long lateral hairs on the shaft; kinetosome usually with four microtubular kinetosomal roots and one large striated root or rhizoplast; ciliary transitional helix with 4–6 gyres located above the major transitional plate; no paraciliary rod; cell coverings, when present, include organic scales, silica scales, organic lorica and cellulose cell wall; chloroplast with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; eyespots present or absent; plastid pigments include chlorophylls *a* and *c1* & *c2*, fucoxanthin, violaxanthin, anthaxanthin and neoxanthin; plastid secondarily lost in some, as noted below.

*Incertae sedis* Chrysophyceae: *Chryososaccus*, *Chrysosphera*, *Cyclonexis*, *Lygynion*, *Phaeoplaca*.

●●●●●●● Chromulinales Pascher 1910

Swimming cells with only one cilium visible by light microscopy; photosynthetic; four microtubular kinetosomal roots. *Chromulina*, *Chrysomonas*.

●●●●●●● Hibberdiales Andersen 1989

Swimming cells with only one cilium visible by light microscopy; photosynthetic; three microtubular kinetosomal roots. *Hibberdia*.

●●●●●●●● Ochromonadales Pascher 1910

Swimming cells with two cilia visible by light microscopy; some secondarily lost photosynthetic ability, and are colourless; heterotrophic species can be phagotrophic. *Spumella*, *Pedospumella*, *Ochromonas*.

●●●●●●● Paraphysomonadida Scoble & Cavalier-Smith 2014

Phagotrophic colourless cells with two visible cilia; scales composed of unperforated base plate, usually circular, with slender simple spines. *Paraphysomonas*.

●●●●●●●● Synrales Andersen 1987

Predominately ciliated photosynthetic cells, some form benthic palmelloid colonies; swimming cells usually with

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●●● Eustigmatales Hibberd 1981</td><td>Coccoid organisms, single cells or colonies; swimming cells biciliate—one anteriorly directed and one posteriorly directed; four microtubular kinetosomal roots and one large striated kinetosomal root or rhizoplast; ciliary transitional helix with six gyres located above the major transitional plate; no paraciliary rod; cell walls present; chloroplast without girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; eyespot present but located outside of the chloroplast; plastid pigments include chlorophylls a, violaxanthin, and vaucherioxanthin. Botryochloropsis, Eustigmatos, Monodopsis, Nannochloropsis, Pseudocharaciopsis, Vischeria.</td></tr><tr><td>●●●●●● Phaeophyceae Hansgirg 1886 [Kjellman 1891; Pfitzer 1894]</td><td>Filamentous, syntagmatic, parenchymatous or ciliated; swimming cells with two cilia usually inserted laterally—one anteriorly directed and one posteriorly directed; usually four microtubular kinetosomal roots but no striated kinetosomal root or rhizoplast; ciliary transitional helix typically with six gyres located above the major transitional plate; no paraciliary rod; little to no substantial tissue differentiation occurring in parenchymatous forms; cell wall present, containing alginate compounds and cellulose; plasmodesmata or pores between cells in parenchymatous forms; chloroplasts with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; eyespots present or absent; plastid pigments include chlorophylls a and c1 & c2, fucoxanthin, and violaxanthin. Note that several subdivisions are separated on the basis of life history and gene sequence information, but taxonomic classification is still in flux.</td></tr><tr><td>●●●●●●● Ascoseirales Petrov 1964</td><td>Sporophyte parenchymatous, with intercalary growth; several scattered discoid plastids without pyrenoid; heteromorphic life cycle but gametophyte not free-living; isogamous sexual reproduction. Ascoseira.</td></tr><tr><td>●●●●●●●● Desmarestiales Setchell & Gardner 1925</td><td>Gametophyte small and filamentous; sporophyte larger and pseudoparenchymatous; several scattered discoid plastids with no pyrenoid; trichothallic growth; heteromorphic life cycle; oogamous sexual reproduction. Arthrocladia, Desmarestia (P), Himantothallus, Phaeurus.</td></tr><tr><td>●●●●●●● Dictyotales Bory de Saint-Vincent 1828</td><td>Gametophyte and sporophyte parenchymatous, with apical or marginal growth; several scattered discoid plastids without pyrenoid; isomorphic life cycle; oogamous sexual reproduction. Dictyota, Dilophus, Lobophora, Padina, Stypopodium, Taonia, Zonaria.</td></tr><tr><td>●●●●●●●● Discosporangiales Kawai et al. 2007</td><td>Simple branched fillaments with apical growth; plastids multiple, discoid, without pyrenoids; species lack heterotrophy and phaeophycean hairs. Note that the early divergence of this group from other brown algae is reflected in their continuous division and elongation of vegetative cells. Choristocarpus, Discosporangium.</td></tr><tr><td>●●●●●●● Ectocarpales Bessey 1907, emend. Silva & Reviers 2000</td><td>Gametophyte and sporophyte uniseriate filaments, either branched or unbranched, with diffuse growth: one or more ribbon-shaped plastids with pyrenoid; isomorphic life cycle; isogamous, anisogamous or oogamous sexual reproduction. Adenocystis, Acinetospora, Asterocladon, Asteronema, Chordaria, Ectocarpus, Scytosiphon.</td></tr><tr><td>●●●●●●● Fucales Bory de Saint-Vincent 1927</td><td>Sporophyte parenchymatous, with apical cell growth; several scattered discoid plastids without pyrenoid; diploid life stage only with meiosis producing gametes; (mostly) oogamous sexual reproduction. Ascophyllum, Bifurcaria, Cystoseira, Druvillaea, Fucus, Hormosira, Sargassum, Turbinaria.</td></tr><tr><td>●●●●●●●● Ishige Yendo 1907 [Ishigeacea Okamura 1935, Ishigeales Cho et al. 2004]</td><td>Isomorphic alternation of generations, with apical cell growth; scattered discoid plastids without pyrenoids; terminal unilocular sporangia or uniseriate plurilocular sporangia; cortex pseudoparenchymatous with assimilatory filaments; phaeophycean hairs in cryptostigmata. Ishige.</td></tr><tr><td>●●●●●●● Laminariales Migula 1908</td><td>Gametophyte small and filamentous with apical growth; sporophyte large and parenchymatous, with intercalary growth; several scattered discoid plastids without pyrenoid; heteromorphic life cycle; oogamous sexual reproduction with eggs sometimes ciliated. Akkesiophycus, Alaria, Chorda, Costaria, Laminaria, Lessonia, Pseudochoda.</td></tr></tbody></table>

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●●●● *Nemoderma* Schousboe ex Bonnet 1892 [Nemodermatales Parente et al. 2008] (M)

Encrusting heterotrichous thalli; numerous discoid plastids per cell without pyrenoids; isomorphic life cycle; anisogamous gametes; plurilocular reproductive structures are lateral, whereas unilocular sporangia are intercalary. *Nemoderma*.

●●●●●●● Onslowiales Draisma & Prud'homme van Reine 2008

An irregularly branched oligostichous thallus, both branches and reproductive structures are the result of lateral divisions from thallus cells; prominent apical cell lacking transverse division of subapical cells; multiple discoid plastids without pyrenoid; isomorphic life cycle; sexual reproduction can occur by plurilocular or unilocular sporangia, or via vegetative propagules lacking a central apical cell. *Onslowia*.

●●●●●●● Ralfsiales Nakamura ex Lim & Kawai 2007

Crustose in at least one phase of the life history or via a disc-type germination; plastids without pyrenoids, from one to many per cell; plurilocular sporangium intercalary and having one or more terminal sterile cells. *Lithoderma*, *Neoralfsia*, *Pseudolithoderma*, *Ralfsia*.

●●●●●●● Scytothamnales Peters & Clayton 1998

Gametophyte large and parenchymatous, with intercalary growth; sporophyte small and filamentous, with apical growth; one or more stellate or axial plastids with pyrenoid; heteromorphic alternation of generations; anisogamous sexual reproduction. *Scytothamnus*, *Splashnidium*, *Stereocladon*.

●●●●●●● Sphacelariales Migula 1908

Gametophyte and sporophyte branched multiseriate filaments, with apical growth; several scattered discoid plastids without pyrenoid; usually an isomorphic alternation of generations; isogamous, anisogamous or oogamous sexual reproduction. *Chaetopteris*, *Halopteris*, *Stypocaulon*, *Sphacelaria*, *Verosphacella*.

●●●●●●● Sporochnales Sauvageau 1926

Gametophyte and larger sporophyte pseudoparenchymatous, with trichothallic growth; several scattered discoid plastids without pyrenoid; heteromorphic alternation of generations; oogamous sexual reproduction. *Bellotia*, *Carpomitra*, *Nereia*, *Sporochonus*, *Tomaculopsis*.

●●●●●●● Syringodermatales Henry 1984

Gametophyte 2-4 cells; sporophyte parenchymatous with apical and marginal growth; several scattered discoid plastids without pyrenoid; heteromorphic alternation of generations but gametophyte not free-living; isogamous sexual reproduction. *Syringoderma*.

●●●●●●● Tilopteridales Bessey 1907

Polystichous construction of the thallus, which grows by a trichothallic meristem; several scattered plastids without pyrenoids; isomorphic alternation of generations; oogamous sexual reproduction. *Cutleria*, *Halosiphon*, *Haplospora*, *Phaeosiphoniella*, *Phyllaria*, *Tilopteris*.

●●●●●● Phaeothamniophyceae Andersen & Bailey in Bailey et al. 1998

Filamentous, capsoid, palmelloid, ciliated, or coccoid; swimming cells biciliated—anteriorly directed cilium bearing tripartite tubular mastigonemes and posteriorly directed cilium without tripartite hairs; four microtubular kinetosomal roots but no striated kinetosomal root or rhizoplast; ciliary transitional helix with 4-6 gyres located above the major transitional plate; no paraciliary rod; cells covered with an entire or two-pieced cell wall; chloroplast with girdle lamella; chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; eyespots present; plastid pigments include chlorophylls *a* and *c*, fucoxanthin, heteroxanthin, diatoxanthin and diadinoxanthin.

●●●●●●● Phaeothamniales Bourrelly 1954, emend. Andersen & Bailey in Bailey et al. 1998 (R)

Distinguished from the Pleurochloridales based upon molecular phylogenetic analyses. *Phaeothamnion*.

●●●●●●● Pleurochloridales Ettl 1956 (R)

Distinguished from the Phaeothamniales based upon molecular phylogenetic analyses. *Pleurochloridella*.

●●●●●● Raphidophyceae Chadefaud 1950, emend. Silva 1980

Naked swimming biciates with one anteriorly directed cilium bearing tripartite tubular mastigonemes and one posteriorly directed cilium lacking tripartite mastigonemes; microtubular kinetosomal roots present but poorly characterized; one large striated kinetosomal root or rhizoplast present; ciliary transitional helix absent; no paraciliary rod; chloroplast with or without girdle lamella; outer chloroplast endoplasmic reticulum membrane with no or very weak direct

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

membrane connection to the outer nuclear envelope membrane; plastid DNA with scattered granule-type genophore; eyespots absent; plastid pigments include chlorophylls *a* and *c1* & *c2*; carotenoid composition distinctly different between marine (*m*) and freshwater (*fw*) species—fucoxanthin (*m*), violaxanthin (*m*), heteroxanthin (*fw*), vaucherioxanthin (*fw*). *Chattonella, Fibrocapsa, Goniostomum, Haramonas, Heterosigma, Merotricha, Olisthodiscus, Vacuolaria*.

●●●●● Schizocladia Henry et al. in Kawai et al. 2003 [Schizocladales Kawai et al. 2003] (M)

Branched filamentous algae with biciliated zoospores—an immature cilium bearing tubular tripartite hairs; ciliary transitional helix with ~5 gyres located above the transitional plate; ciliary apparatus and kinetosomal roots, if present underscribed; chloroplasts parietal with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; plastids with chlorophylls *a* and *c* as well as carotenoids (unverified); cell wall containing alginates but lacking cellulose and plasmodesmata; eyespot present; major storage product undescribed. *Schizocladia*.

●●●●● Xanthophyceae Allorge 1930, emend. Fritsch 1935 [Heterokontae Luther 1899; Heteromonadea Leedale 1983; Xanthophyta Hibberd 1990]

Predominately coccoid or filamentous, rarely amoeboid, ciliated or capsoid; swimming cells with two cilia—one anteriorly directed and bearing tripartite tubular hairs and one posteriorly directed and lacking tripartite hairs; four microtubular kinetosomal roots and one large striated kinetosomeal root or rhizoplast; ciliary transitional helix with six apparently double gyres located above the major transitional plate; no paraciliary rod; cell walls typical, probably of cellulose and either entire or H-shaped bisectional walls; chloroplast with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; eyespots present or absent; plastid pigments include chlorophylls *a* and *c1* & *c2*, violaxanthin, heteroxanthin, and vaucherioxanthin.

●●●●●●● Tribonematales Pascher 1939

Filamentous, coccoid, and capsoid forms, sometimes becoming parenchymatous or multinucleate with age; cell walls, when present, either with H-shaped overlapping cell wall pieces or with complete or entire cell walls; elaborate reproductive structures lacking. *Botrydium, Bumilleriopsis, Characiopsis, Chloromeson, Heterococcus, Monadus, Ophiocytium, Sphaerosorus, Tribonema, Xanthonema*.

●●●●●●●● Vaucheriales Bohlin 1901

Siphonous filaments; elaborate sexual reproductive structures as antheridia and oogonia. *Vaucheria*.

●●●●● Diatomista Derelle et al. 2016, emend. Cavalier-Smith 2017 (R)

Unicellular or aggregative; no cell wall; naked or with silica frustules or scales; without supra-tz helix
*Incertae sedis* Diatomista: Environmental lineages MOCH-1, MOCH-2, MOCH-4 Massana et al. 2014

Uncultured groups detected in molecular marine surveys amplifying directly 18S rDNA genes. These clades are mostly detected in the analysis of small size fractions (pico and nanoeukaryotes).

●●●●●● Bolidophyceae Guillou et al. 1999 [Parmales Booth and Marchant 1987]

Two types of cells known: motile and nonmotile. Swimming cells with two cilia, one anteriorly directed (with mastigones) and one posteriorly directed: no microtubular or fibrillar kinetosomal roots; ciliary transitional helix absent; no paraciliary rod; chloroplast with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with ring-type genophore; no eyespot; plastid pigments include chlorophylls *a* and *c* 1-3, fucoxanthin, 19'-butanoyloxyfucoxanthin, diatoxanthin and diadinoxanthin. Non-motile cells possess chloroplasts like those of swimming cells but are surrounded by complete multipartite walls comprised of abutting silica plates (circular shield and ventral plates, elongate or triradiate girdle plates, and triradiate dorsal plates), often bearing ridges and spines and radiating lines of pores; exclsuively marine. *Bolidomonas, Triparma, Tetraparma, Pentalamina*.

●●●●●● Diatomeae³⁴ Dumortier 1821 [= Bacillariophyta Haeckel 1878]

Vegetative cells cylindrical with a circular, elongate or multipolar cross-section, lacking any trace of cilia except in the sperm of centric lineages; cell wall complete, composed of tightly integrated silicified elements and comprised of two valves, one at each end of the cell, with several girdle bands (as hoops or segments) covering the cylindrical 'girdle' lying between the valves; valves penetrated by simple or chambered pores arranged in rows (striae); other openings often present in the valves (so-called 'fields' and 'processes', slits), involved in secretion and motility; chloroplasts usually present, bounded by four membranes, and with lamellae of three thylakoids and a ring nucleoid (rarely multiple nucleoids); ciliated sperm cells bearing a single anterior cilium with a 9 + 0 axoneme and mastigonemes; life cycle diplontic and of unique pattern—slow size reduction over several years during the vegetative phase, caused by an unusual internal wall morphogenesis, alternating with rapid size restitution via a growth phase (auxospore) over several days.

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●●● Leptocylindrophytina D.G. Mann, in Adl et al. 2019
Chain-forming or solitary; valves circular, valve pattern radiating from a central circular annulus; pores simple; girdle bands segmental to strap-like; sexual reproduction oogamous or apparently absent; chloroplasts several, small; exclusively marine.

●●●●●●● Leptocylindrophyceae D.G. Mann, in Adl et al. 2019
Chain-forming (linked by short spines or secretions), delicate; valves circular, flat-topped or domed; a single simple process often present near the annulus; girdle bands segmental; auxospore forming a dormant resting stage (rare in other diatom clades). *Leptocylindrus*, *Tenuicylindrus*.

●●●●●●●● Corethrophyceae D.G. Mann, in Adl et al. 2019
Solitary; valves circular, domed; elaborate articulating silica spines secreted from around the valve margin; rimoportulae and other processes absent; girdle bands segmental. *Corethron*.

●●●●●● Ellerbeckiophytina D.G. Mann, in Adl et al. 2019
Chain-forming (linked by valve spines), heavily silicified; valves circular, with radially symmetrical valve pattern; rimoportulae or tube processes small, restricted to the mantle; girdle bands hoop-like; marine and freshwater; sexual reproduction as yet unknown. *Ellerbeckia*.

●●●●●●● Probosciphytina D.G. Mann, in Adl et al. 2019
Usually solitary, with a long pervalvar axis; valves circular, extended into an eccentric beak (proboscis); rimoportulae and other processes absent; girdle bands segmental; exclusively marine; sexual reproduction oogamous. *Proboscia*.

●●●●●● Melosirophytina D.G. Mann, in Adl et al. 2019
Usually chain-forming (linked by valve spines or by central secretions); valves circular, radially symmetrical, pattern radiating from a central annulus (which may occupy the whole of the valve face in *Aulacoseira* and some *Melosira*); rimoportulae small, scattered on the valve face or marginal; girdle bands hoop-like or segmental; marine and freshwater; sexual reproduction oogamous. *Aulacoseira*, *Melosira*, *Hyalodiscus*, *Stephanopyxis*, *Paralia*, *Endictya*.

●●●●●●● Coscinodiscophytina Medlin & Kaczmarska 2004, emend.
Solitary, robust; valves generally circular, pattern radiating from a central, subcentral or submarginal circular annulus; valve structure chambered; rimoportulae central, scattered on the valve face, or in a submarginal ring, sometimes with slit-like apertures, tubes or cap-like structures externally; girdle bands hoop-like; sexual reproduction oogamous; mostly marine. *Actinopychus*, *Coscinodiscus*, *Actinocyclus*, *Asteromphalus*, *Aulacodiscus*, *Stellarima*.

●●●●●● Rhizosoleniophytina D.G. Mann, in Adl et al. 2019
Chain-forming, rarely solitary; valves circular, radially symmetrical or with the annulus displaced towards one side; valve structure simple; rimoportulae single, associated closely with the annulus, sometimes developed externally into a spine; girdle bands segmental; sexual reproduction oogamous; marine. *Guinardia*, *Rhizosolenia*, *Pseudosolenia*.

●●●●●●● Arachnoidiscophytina D.G. Mann, in Adl et al. 2019
Solitary, heterovalvar; valves circular, radially symmetrical; valve structure chambered, complex; valve centre with radial slits (apparently modified rimoportulae); girdle bands hoop-like; sexual reproduction incompletely known, marine. *Arachnoidiscus*.

●●●●●● Bacillariophytina Medlin & Kaczmarska 2004, emend.
Chain-forming, colonial or solitary; valve outline bipolar or multipolar, rarely circular; valve pattern radiating from a central circular or elongate annulus or from a longitudinal rib (sternum); valve structure simple or chambered; areas of special pores or slits often present, involved in mucilage secretion; rimoportulae present or absent; girdle bands usually hoop-like; sexual reproduction oogamous with nonmotile eggs and unilibrate sperm, or isogamous with amoeboid or non-ciliate 'spinning' gametes; auxospore usually with band-like elements (the 'perizonium') that facilitate anisometric expansion; chloroplasts many, few or one, very rarely apochlorotic.

●●●●●●●● Mediophyceae Jouse & Proshkina-Lavrenko in Medlin & Kaczmarska 2004
Chain-forming or solitary; valve outline bipolar or multipolar, sometimes (perhaps secondarily) circular; valve pattern radiating from a circular or elongate annulus; rimoportulae central or marginal; sexual reproduction oogamous; auxospore with scales and/or perizonium; chloroplasts usually many, small.

(continued)

<footnote n="34">³⁴This revision reflects numerous advances in the phylogeny of the diatoms over the last decade. Due to our poor taxon sampling outside of the Mediophyceae and pennate diatoms, and the known and anticipated diversity of all diatoms, many clades appear at a high classification level (and the higher level classification is rather flat). Nomenclature follows the botanical code (ICN). Some of the basal nodes will probably become better resolved in the future, and would permit additional subdivisions. The genera are provided as examples only, and are far from complete lists.</footnote>
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●●●●● Chaetocerotophycidae Round & R.M. Crawford in Round et al. 1990, emend.
Mostly chain-forming (attached by the valve poles and setae, where present, or by pads) delicate plank-
tonic species; valve outline usually bipolar, usually with projections or horns at the poles, rarely multipo-
lar or circular; pore fields present at the poles, often also long hollow setae; annulus central or
submarginal; rimoportulae central or submarginal; mostly marine, but with a few large robustly silicified
freshwater forms. *Chaetoceros, Bacteriastrum, Dactyliosolen, Cerataulina, Hemiaulus, Eucampia, Acan-
thoceras, Urosolenia, Terpsinoë, Hydrosera*.

●●●●●●●● Lithodesmiophycidae Round & R.M. Crawford in Round et al. 1990, emend.
Chain-forming (linked by the valve poles and/or central region) or solitary; valve outline bi-, tri- or to mul-
tipolar; valve structure simple, with valve pattern radiating from a central annulus or a scatter of pores;
valve poles lacking well-defined pore fields; rimoportula present, central (within the annulus), some-
times extended externally into a long tube. *Lithodesmium, Lithodesmioides, Helicotheca, Bellerochea,*
*Ditylum*.

●●●●●●●● Thalassiosiphycidae Round & R.M. Crawford in Round et al. 1990
Cells connected into chains by chitin threads, colonial (forming sheets), or solitary; valve outline almost always circular; valve pattern generally organized radially about a central annulus; valve structure simple or chambered; generally with one or two submarginal rimoportulae; almost all members characterized by 'fultoportulae' (special processes involved in chitin thread secretion); auxospores lacking perizonia; marine and freshwater. *Thalassiosira, Lindavia, Cyclotella, Stephanodiscus, Cyclostephanos, Discostella, Bacteriosira, Skeletonema, Detonula*.

●●●●●●●● Cymatosiphycidae Round & R.M. Crawford in Round et al. 1990
Generally chain-forming (linked by spines on the valves), very small-celled, delicate forms; often heterovalvar; valve outline bipolar; valve pattern sometimes organized about a central annulus but more often with scattered pores; small well-defined pore fields ('ocelluli') present at the apices and some valves often bearing long spines ('pili'); a single rimoportula near the centre of some valves; exclusively marine. *Cymatosira, Minutocellus, Papiliocellulus, Leyanella, Extubocellulus, Plagiogrammopsis, Campylosira, Brockmanniella, Pierrecomperia*.

●●●●●●●● Odontellophycidae, D. G. Mann, in Adl et al. 2019
Chain-forming (linked by mucilage pads) or solitary, generally large-celled and sometimes very robust; valve outline bi- or multipolar, rarely circular; valve pattern organized radially about a central circular or elongate annulus; valve structure simple or chambered; valve poles with well-defined pore fields ('ocelli') often surrounded by a thick rim; rimoportulae present (sometimes with long external tubes) or absent; exclusively marine. *Odontella, Triceratium, Cerataulus, Pleurosira, Pseudauliscus, Amphitetras, Trieres, Mastodiscus*.

●●●●●●●● Chrysanthemodiscophycidae, D.G. Mann, in Adl et al. 2019
Chain-forming (linked by mucilage pads) or solitary; valve outline circular, bipolar (and then sometimes extremely elongate, either isopolar or heteropolar) or multipolar; valve pattern organized radially about a central annulus, which can be circular or extremely elongate (and then with striae extending inwards from the annulus, which is therefore 'bifacial'); valve structure simple or chambered (alveolate); rimoportulae present or absent; pore fields present at the poles (and then poorly differentiated, i.e. 'pseudocelli') or absent; exclusively marine. *Chrysanthemodiscus, Biddulphiopsis, Trigonium, Isthmia, Lampriscus, Stictocyclus, Ardissonea, Climacosphenia, Toxarium*.

●●●●●●●● Biddulphiphyceae, D. G. Mann, in Adl et al. 2019
Chain-forming or solitary; valve outline bipolar, with elevated projections at the poles; valve pattern radiating from a circular or elongate annulus; valve structure simple; rimoportulae present; exclusively marine.

●●●●●●●● Biddulphiophycidae Round and R.M. Crawford in Round et al. 1990, emend.
Chain-forming (linked by mucilage pads), generally large-celled and robust; valve outline sometimes undulate; polar projections small or large and valve often with additional doming centrally and sometimes between centre and poles; pattern organized radially about a central circular annulus; pore fields ('pseudocelli') present at the poles; rimoportulae central. *Biddulphia*.

●●●●●●●● Attheya T. West 1860c
Delicate, solitary; valve outline bipolar, the ends developed into narrow setae; valve pattern radiating

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

from an elongate annulus; pore fields absent, though the setae may end in specialized regions with
spines; a single off-central rimoportula; sexual reproduction oogamous; exclusively marine. *Attheya*.

●●●●●●●● Bacillariophyceae Haeckel 1878, emend.

Chain-forming, colonial or solitary; valve outline almost always bipolar; valve pattern organized bilaterally about an elongate axial rib (sternum), as in a feather; valve structure simple or chambered; rimoportulae generally only one or two per valve or none, sometimes accompanied (or replaced?) by special slits (the 'raphe') involved in motility; sexual reproduction involving gametangiogamy and almost always with gametes of equal size (although sometimes with behavioural differentiation and/or morphological differences); perizonium generally differentiated into two distinct series, transverse and longitudinal; chloroplasts usually only one, two or a few and large, less often many and small.

●●●●●●●●● Striatellaceae Kützing 1844

Solitary; valve outline bipolar; valve structure simple; a rimmed pore field present at each pole; rimpor-
tulae present (one at each pole or scattered along the sides of the valve); raphe absent; sexual repro-
duction not confirmed; exclusively marine. *Striatella, Pseudostiatella*.

●●●●●●●●● Urneidophycidae Medlin 2016 (P?)

Chain-forming (linked by spines on the valves), colonial (linked by pads) or solitary; valve outline bi- or
multipolar, rarely circular; valve structure simple; pore fields sometimes present at the poles, rimpor-
tulae present or absent; raphe absent; 'male' and 'female' gametes of equal size but 'male' gametes
with non-cilium projections that generate movement; exclusively marine. *Plagiogramma, Dimere-
gramma, Rhaphoneis, Delphineis, Psammoneis, Bleakeleya, Asterionellopsis*.

●●●●●●●●● Fragilariophycidae Round in Round, Crawford & Mann 1990, emend.

Chain-forming or colonial (linked by pads or stalks, less often by valve spines) or solitary; valve outline bi- or multipolar, very rarely circular (with reduction of the sternum and secondary evolution of radial symmetry); valve structure usually simple; pore fields (rimmed or not) often present at the poles; rimoportulae present or absent, very variable in location but often polar; raphe absent; 'male' and 'female' gametes of equal or unequal size, amoeboid, or with 'male' gametes with non-cilium projections that generate movement; marine and freshwater. *Fragilaria, Synedra, Tabellaria, Asterionella, Diatoma, Tabularia, Cyclophora, Astrosyne, Licmophora, Rhabdonema, Grammatophora, Staurosira, Thalassionema*.

●●●●●●●●● Bacillariophycidae D.G. Mann in Round, Crawford & Mann 1990, emend.

Usually solitary and motile, less often chain-forming or colonial (linked by stalks or living in mucilage tubes); valve outline almost always bipolar, frustules sometimes heterovalvar; rimoportulae usually absent (exception: Eunotiales); valve structure simple or chambered; pore fields sometimes present at one or both poles; raphe present (rarely infilled during valve formation); usually one or two chloroplasts per cell, positioned to avoid the area beneath the raphe; gametes morphologically similar, amoeboid or fusing through expansion; marine and freshwater, with many examples of genera or families transgressing the marine–freshwater interface. The vast majority of diatom species belong here, classified into many tens of genera. *Eunotia, Achnanthes, Bacillaria, Nitzschia, Pseudo-nitzschia, Cylindrotheca, Navicula, Seminavis, Haslea, Stauroneis, Pleurosigma, Gyrosigma, Achnanthidium, Cocconeis, Frustulia, Diploaneis, Sellaphora, Pinnularia, Gomphonema, Cymbella, Didymosphenia, Phaeodactylum, Amphora, Entomoneis, Epithemia, Surirella*.

●●●●● Dictyochophyceae Silva 1980

Single cells, colonial ciliated cells or amoebae; swimming cells usually with one cilium, anteriorly directed and bearing tripartite tubular hairs; kinetosomes adpressed to nucleus; no microtubular or fibrillar kinetosomal roots; ciliary transitional helix, when present, with 0-2 gyres located below the major transitional plate; paraciliary rod present; cells naked, with organic scales or with siliceous skeleton; chloroplasts, when present, with girdle lamella; plastid DNA with scattered granule-type genophore; no eyespot; plastid pigments include chlorophylls a and c 1 & 2, fucoxanthin, diatoxanthin and diadinoxanthin.

●●●●●●●● Dictyochales Haeckel 1894

Silica skeleton present on at least one life stage; with chloroplasts. *Dictyocha*.

●●●●●●●●● Pedinellales Zimmermann et al. 1984

Naked, organically scaled or loricate ciliated cells; with or without chloroplasts. *Actinomonas, Apedinella, Ciliophrys, Mesopedinella, Palatinella, Pedinella, Pseudopedinella, Pteridomonas*.

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

Rhizochromulinales O'Kelly & Wujek 1994
Vegetative cells amoeboid; zoospore ciliated; with chloroplasts. *Rhizochromulina*.

Pelagophyceae Andersen & Saunders 1993
Ciliated, capsoid, coccoid, sarcinoid or filamentous; swimming cells with one or two cilia—anteriorly directed cilium bearing bipartite or tripartite tubular hairs and second cilium, when present, directed posteriorly; kinetosome(s) adpressed to nucleus; no microtubular or fibrillar kinetosomal roots on uniciated cells; four microtubular roots on bicili-ated cells; ciliary transitional helix, when present, with two gyres located below the major transitional plate; paraciliary rod present or absent; cells naked or with organic thecae or cell walls; chloroplasts with girdle lamella; plastid DNA with scattered granule-type genophore; no eyespot; plastid pigments include chlorophylls *a* & *c* 1, 2, fucoxanthin, 19-hexa-noyloxyfucoxanthin, 19-butanoyloxyfucoxanthin, diatoxanthin and diadinoxanthin.

Pelagomonadales Andersen & Saunders 1993
Ciliated or coccoid organisms; when ciliated, a single cilium without a second kinetosome; no kinetosomal roots. *Aureococcus*, *Aureoumbra*, *Pelagococcus*, *Pelagomonas*.

Sarcinoïd, capsoid, ciliated or filamentous; cells typically with organic cell wall; ciliated cells biciated with four microtubular kinetosomal roots. *Ankylochrisis*, *Nematochrysopsis*, *Pulvinaria*, *Sarcinochrysis*.

Pinguiophyceae Kawachi et al. 2003
Ciliated or coccoid organisms; swimming cells with one or two cilia; tripartite hairs present or absent on immature cilium; 3-4 microtubular kinetosomal roots and one large striated kinetosomal root or rhizoplast; ciliary transitional helix with two gyres located below the major transitional plate; no paraciliary rod; cells naked or enclosed in mineralized loriga; chloroplast with girdle lamella; outer chloroplast endoplasmic reticulum membrane with direct membrane connection to the outer nuclear envelope membrane; plastid DNA with scattered granule-type genophore; eyespots absent; plastid pigments include chlorophylls *a* and *c1* & *c2*, fucoxanthin, and violaxanthin. *Glossomastix*, *Phaeomonas*, *Pinguichrysis*, *Pinguiococcus*, *Polypodochrysis*.

● **Alveolata** Cavalier-Smith 1991
Cortical alveolae, sometimes secondarily lost; with ciliary pit or micropore; mitochondrial cristae tubular or ampulliform.

●● Colpodellida Cavalier-Smith 1993, emend. Adl et al. 2005, 2019
Photosynthetic, or non-photosynthetic and predatory; complex plastids, when present bound by four membranes; mitochondrion with tubular cristae; highly flattened cortical alveoli; microtubules beneath alveolae; conoid-like structure with apical complex and rostrum; biciliate; micropore present; cysts at least in some species.

Vitrellaceae Oborník & Lukeš 2012
Immotile vegetative cells with laminated cell walls; autosporangia and zoosporangia contain dozens of immotile autospores and motile biciliate zoospores, respectively; prominent pyrenoid; sporangia carry an operculum; plastid pigmented by chlorophyll *a*, violaxanthin, vaucheria xanthin and β-carotene; chlorophyll *c* absent. *Vitrella*.

●●● Colpodellaceae Adl et al. 2019
Non-photosynthetic ciliated cell predatory on other protists, (found once in human blood). *Colpodella*, *Chilovora*, *Voromonas*.

●●●● Chromeraceae Oborník & Lukeš 2012
Immotile coccoid cells reproduce by binary division; zoospores with heterodynamic cilia; pseudoconoid, coccoid wedge and chromosome present; cells surrounded by thin sporangium wall; plastid pigmented by chlorophyll *a*, violaxanthin, isofucoxanthin and β-carotene; chlorophyll *c* absent. *Chromera*.

●●●● Alphamonaceae Adl et al. 2019
Non-photosynthetic predatory ciliated cells on other protists; carbohydrate reserve granules absent. *Alphamonas*.

●● Perkinsidae Levine 1978, emend. Adl et al. 2005 [Perkinsozoa Moestrup & Rehnstam-Holm 1999; Perkinsozoa Norén & Moestrup 1999]

Trophozoites parasitic, dividing by successive binary fissions; released trophozoites (termed hypnospores) developing outside host to form zoospores via the formation of zoosporangia or morphologically undifferentiated mononucleate cells via a hypha-like tube; zoospores biciilate; apical organelles including an incomplete conoid (open along one side), rhoptries, micronemes and micropores, and a microtubular cytoskeleton with both an anterior and posterior polar ring. *Dinovorax*, *Snorkelia*, *Parvilucifera*, *Perkinsus*, *Rastrimonas*, X-cell parasites.

*Incertae sedis* Perkinsidae: *Psammosa* Okamoto et al. 2012—morphologically close to *Colpodella* and *Voromonas*, but phylogenetically

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

more related to Perkinsidae.

*Incertae sedis* Perkinsidae: *Phagodinium*.

●● Colponemida Cavalier-Smith 1993 emend. Adl et al. 2019 (P?)

Biciliate alveolates, typically cytotrophic predators, found in soil, freshwater and marine environments. These described genera are most probably multiple genera as DNA sequences obtained are divergent and many remain to be described. Poorly sampled due to cytotrophy, we expect better taxon sampling to improve the resolution of this node.

●●● Colponemidia Tikhonenkov et al. 2014

Biciliate; three-membraned alveolar pellicle; two microtubule bands armour longitudinal groove; micropore absent; nontubular mastigonemes present; cytotrophic predators and sometimes on microinvertebrates. *Colponema*.

●●● Acavomonidia Tikhonenkov et al. 2014

Biciliate; rigid cells; lack longitudinal grooves and apical complex structures; cytotrophic predators. *Acavomonas*.

●●● Palustrimonas Patterson & Simpson 1996

Deep branching colponemid alveolate; cytotrophic predator; longitudinal feeding groove. *Palustrimonas*.

●●● *Oxyrrhis* Dujardin 1841 [Oxyrrhinaceae Sournia 1984] (M)

Without true cingulum and sulcus; intranuclear mitotic spindle; with amphiesmal vesicles and trichocysts; cilia inserted laterally; cytotrophic predator. (There may be multiple species). *Oxyrrhis marina*.

●● Dinoflagellata Bütschli 1885, emend. Fensome et al. 1993, emend. Adl et al. 2005

Cells with two cilia in the motile stage—typically, one transverse cilium ribbon-like with multiple waves beating to the cell's left and longitudinal cilium beating posteriorly with only one or few waves; nucleus typically a dinokaryon with chromosomes remaining condensed during interphase and lacking typical eukaryotic histones and centrioles; dinoflagellate/viral nucleoproteins package chromatin; closed dinomitosis with extranuclear spindle.

*Incertae sedis* Dinoflagellata: Naked and thecate genera with uncertain affiliation, e.g. *Adenoides*, *Akashiwo*, *Amphidiniella*, *Ankistrodinium*, *Apicoporus*, *Archaeosphaerodiniopsis*, *Bispinodinium*, *Bysmatrum*, *Cabra*, *Cladopyxis*, *Cryptthecodinium*, *Cucumeridinium*, *Dactylinodinium*, *Dicroerisma*, *Gloeodinium*, *Grammatodinium*, *Gynogonadinium*, *Gyrodiniellum*, *Halostylodinium*, *Heterodinium*, *Moestrupia*, *Paragymnodinium*, *Phytodinium*, *Plagiodinium*, *Planodinium*, *Pileidinium*, *Pseudadenoides*, *Pseudothecadinium*, *Pyramiddinium*, *Rhinodinium*, *Roscoffia*, *Sabulodinium*, *Sphaerodinium*, *Spiniferodinium*, *Testudodinium*, *Thecadinium*, *Thecadiniopsis*, *Togula*.

*Incertae sedis* Dinoflagellata: Parasitic dinoflagellates with dinokaryon during part of the life cycle only; not highly vacuolated. Fossils unknown. [Blastodiniales Chatton 1906, no longer valid]. *Amyloodinium*, *Apodinium*, *Cachonella*, *Caryotoma*, *Crepidoodinium*, *Haplozoon*, *Oodinium*, *Myxodinium*, *Piscinoodinium*, *Protoodinium*, *Rhinodinium*, *Schyzochitriodinium*, *Stylodinium*.

●●●● Syndiniales Loeblich III 1976

Aplastidic intracellular parasites of marine protists and metazoan, generally surrounded by an external parasitophorous membrane inside the host; sporogenesis by palintomic (schizogonous) divisions; motile cells (i.e. dinospores or gametes) with a dinokont-like arrangement of cilia; lacking well-defined cingulum and sulcus; transverse cilium wrapping loosely around cell. V-shaped chromosomes, attach to the nucleus membrane by the apex and remain condensed during interphase. Although there is a strong morphological argument for the common origin of the Syndiniales (all MALVs together) based on synapomorphies, their monophyly is not always supported by SSU analysis and more phylogenetic analysis is required. *Amoebophrya*, *Duboscquella*, *Merodinium*, *Syndinium*.

*Incertae sedis* Syndiniales: *Ichthyodinium* (environmental Marine Alveolate (MALV) Group I). Parasites of the early developmental stages (eggs and larvae) of some species of finfish; sporogenesis occurs in the yolk sac of embryos.

*Incertae sedis* Syndiniales: *Ellobiopsidae*: the clade is closely related to MALV-I and MALV-II. *Ellobiopsis*, *Thalassomyces*.

●●●●● Euduboscquellidae Coats & Bachvaroff 2012

Parasites of Ciliophora and Radiolaria, with trophont episome bordered by a perinematic ring and a lamina pharyngea extending into trophont cytoplasm; sporogenesis occurs outside the host (or outside the central capsule). *Euduboscquella* (environmental Marine Alveolate Group I), *Dogelodinium*, *Keppenodinium*.

*Incertae sedis*: RP-parasite, parasite of copepods (environmental Marine Alveolate Group I).

●●●● Amoebophryidae Cachon 1964 (environmental Marine Alveolate Group II)

Parasites of Dinophyceae, Radiolaria and Ciliophora; feeding through a cytopharynx inside the host; palintomic schizogonous divisions occur inside the host and produce a swimming multicellular temporary structure (termed vermiform) after an evaporation to leave its host, then each cell of this structure individualize into dinospore(s). *Amoebophrya*.

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●● Syndinidae Chatton 1910 (environmental Marine Alveolate Group IV)<br>Parasites of crustacean and Radiolaria. Sporogenesis occurs inside the host, and start by active nucleic divisions into a plasmodium that generally fill the whole body of the host; sporogenesis occurs inside the host by fragmentation of the plasmodium. Hematodinium, Syndinium, Solenodinium.</td><td></td></tr><tr><td>●●●● Sphaeriparaceae Loeblich III 1970<br>Parasites of Appendicularia and Radiolaria; feeding through a cytopharynx inside the host; sporogenesis occurs outside the host. Atlanticellodinium, Sphaeripara.</td><td></td></tr><tr><td>●●● Noctilucales Haeckel 1894 [Noctiluciphyceae Fensome et al. 1993]<br>Principal life cycle stage comprising a large free-living motile cell inflated by vacuoles; dinokaryon during part of life cycle only. Fossils unknown. Abedinium, Cachonodinium, Craspedotella, Cymbodinium, Kofoidinium, Leptodiscus, Noctiluca, Petalodinium, Pomatodinium, Scaphodinium, Spatulodinium.</td><td></td></tr><tr><td>●●● Dinophyceae Pascher 1914<br>Cell cortex (amphiesma) containing alveolae (amphiesmal vesicles) that may or may not contain cellulosic thecal plates, the pattern (tabulation) thus formed being a crucial morphological criterion in recognizing affinities among dinophyceans; with a dinokaryon through the entire life cycle.</td><td></td></tr><tr><td>●●●● Gymnodiniphycidae Fensome et al. 1993<br>With numerous amphiesmal vesicles, arranged nonserially or in more than six latitudinal series or with the pellicle as the principal amphiesmal element or the amphiesmal structure uncertain but not comprising a theca divisible into six or fewer latitudinal plates. Few known fossil representatives.</td><td></td></tr><tr><td>●●●●● Gymnodinium F. Stein 1878, emend. G. Hansen & Moestrup in Daugbjerg et al. 2000 sensu stricto<br>With loop-shaped, anticlockwise apical structure complex. Barrufeta, Chytriodinium, Dissodinium, Erythropsidinium, Greuetodinium, Gymnodinium, Lepidodinium, Nematodinium, Nusuttodinium, Pellucidodinium, Polykrikos, Proterythopsis, Warnowia.</td><td></td></tr><tr><td>●●●●● Amphidinium Claparède & Lachmann 1859, emend. Flø Jørgensen et al. 2004 sensu stricto<br>Minute irregular triangular- or crescent-shaped episome deflected to the left; no apical structure complex. Amphidinium.</td><td></td></tr><tr><td>●●●●● Gyrodinium Kofoid & Swezy 1921, emend. G. Hansen and Moestrup in Daugbjerg et al. 2000 sensu stricto<br>Elliptical apical structure complex, bisected by a ridge; with surface striation/ridges. Gyrodinium.</td><td></td></tr><tr><td>●●●●●● Kareniaceae Bergholtz et al. 2005<br>Furrow-like straight or sigmoid apical structure complex; haptophyte-derived chloroplasts. Brachidinium, Karenia, Karloodinium, Takayama.</td><td></td></tr><tr><td>●●●●●● Ceratoperidiniaceae Loeblich III 1980, emend. Reñé and de Salas 2013<br>Closed, circular loop-shaped apical structure complex. Ceratoperidinium, Kirithra.</td><td></td></tr><tr><td>●●●●●●● Torodiniales Boutrup, Moestrup & Daugbjerg 2016<br>Hat-like apical projection; counterclockwise spiralling apical structure complex; with longitudinal surface striation; very large episome. Kapelodinium, Torodinium.</td><td></td></tr><tr><td>●●●●●●●● Levanderina Moestrup et al. 2014<br>U-shaped apical structure complex. Levanderina.</td><td></td></tr><tr><td>●●●●●● Margalefidinium F. Gómez, Richlen & D.M. Anderson 2017<br>U-shaped apical structure complex connected to the sulcal extension; sulcus encircles the cell about once; cingulum encircles the cell about twice; smooth cell surface; eyespot in the episome. Margalefidinium.</td><td></td></tr><tr><td>●●●●●●● Cochlodinium F. Schütt emend. F. Gómez, Richlen & D.M. Anderson 2017 sensu stricto<br>circular apical structure complex connected to the sulcal extension; sulcus invades the episome as a wide loop; descending cingulum encircles the cell about 1.5-2 times; cell surface with fine striations. Cochlodinium strangulatum.</td><td></td></tr><tr><td>●●●●●●●●● Ptychodiscales Fensome et al. 1993<br>With wall of the motile cell dominated by a thick pellicle; alveolae, where discernible, usually devoid of thecal plates,</td><td></td></tr></tbody></table>

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

forming a tabulation that is nonserially arranged or is organized into numerous latitudinal series. Few known fossil representatives. *Achradina*, *Amphilothus*, *Balechina*, *Ptychodiscus*, *Sclerodinium*.

●●●●● Borghiellaceae Moestrup, Lindberg, & Daugbjerg 2009

With or without apical pair of elongate vesicles (PEV) with furrow; eyespot type B with globules inside the chloroplast associated with external brick-like material in vesicles. *Baldinia*, *Borghiella*.

●●●●● Tovelliaceae Moestrup et al. 2005

With alveolae containing light thecal plates with apical line of narrow plates (ALP); eyespot type C with extraplastidal, nonmembrane bound pigment globules. *Bernardinium*, *Esoptrodinium*, *Jadwigia*, *Tovellia*.

●●●●● Suessiaceae Fensome et al. 1993, emend. Moestrup et al. 2009

With alveolae containing light thecal plates and forming a tabulation involving 7–15 latitudinal series, with or without elongate apical vesicle (EAV); eyespot type E with cisternae containing brick-like material. *Ansanella*, *Asulcocephalium*, *Biecheleria*, *Biecheleriopsis*, *Leiocephalium*, *Pelagodinium*, *Polarella*, *Prosoaulax*, *Protodinium*, *Symbiodinium*, *Yihiella*.

●●●●● Peridiniphycidae Fensome et al. 1993

With a tabulation that accords with, or derives from, a pattern in which there are five or six latitudinal plate series; sagittal suture lacking.

●●●●●● Gonyaulacales Taylor 1980

Alveolae usually containing thecal plates, forming a tabulation of 5–6 latitudinal series; distinguished by particular tabulation features that can be recognized generally by a strong degree of asymmetry in the anterior (apical) and posterior (antapical) areas. This taxon has fossils extending from the late Triassic period (~210 Ma) to the present day. *Alexandrium*, *Amylax*, *Ceratium*, *Ceratocorys*, *Coolia*, *Fukuyoa*, *Fragilidium*, *Gambierdiscus*, *Goniodoma*, *Gonyaulax*, *Lingulodinium*, *Ostreopsis*, *Pentaplacodinium*, *Peridiniella*, *Protoceratium*, *Pyrocystis*, *Pyrodinium*, *Pyrophacus*, *Tripos*.

●●●●●● Peridiniales Haeckel 1894

Alveolae containing thecal plates, forming a tabulation of 6 latitudinal series; distinguished by particular tabulation features that can be recognized generally by a strong degree of symmetry in the anterior (apical) and posterior (antapical) areas. This taxon has fossils extending from the early Jurassic Period (~190 Ma) to the present day. *Amphidiniopsis*, *Archaeperidinium*, *Blastodinium*\*, *Diplopelta*, *Diplopsalis*, *Diplopsalopsis*, *Herdmania*, *Niea*, *Oblea*, *Palatinus*, *Parvodinium*, *Peridinium*, *Peridiniopsis*, *Preperidinium*, *Protoperidinium*, *Qia*, *Vulcanodinium*.

●●●●● Thoracosphaeraceae Schiller 1930

Calcareous species and non-calcareous relatives. *Aduncodinium*, *Amyloodinium*, *Apocalathium*, *Blastodinium*, *Chimondinium*, *Cryptoperidiniopsis*, *Duboscquodinium*, *Ensiculifera*, *Leonella*, *Luciella*, *Naiadinium*, *Paulsenella*, *Pentapharsodinium*, *Pfiesteria*, *Scrippsiella*, *Stoeckeria*, *Theleodinium*, *Thoracosphaera*, *Tintinnophagus*, *Tyrannodinium*.

●●●●●● Podolampadaceae Lindemann 1928

No compressed cingulum but homologous plate series. *Blepharocysta*, *Gaarderiella*, *Heterobractum*, *Lissodinium*, *Mysticella*, *Podolampas*.

●●●●● Kryptoperidiniaceae Lindemann 1925 (= "dinotoms")

Genera with diatom-derived chloroplasts and reduced peridinin-chloroplast as eyespot; thecate and athecate taxa, e.g. *Blixaea*, *Durinskia*, *Galeidinium*, *Kryptoperidinium*, *Unruhdinium*.

●●●●● Heterocapsaceae Fensome et al. 1993

Alveolae containing thecal plates, forming a tabulation of six latitudinal series; scales. *Heterocapsa*.

●●●●●● Amphidomataceae Sournia 1984

Alveolae containing thecal plates, forming a tabulation of 5-6 latitudinal series. *Amphidoma*, *Azadinium*.

●●●●●● Oxytoxaceae Lindemann 1928

Alveolae containing thecal plates, forming a tabulation of 5-6 latitudinal series; one antapical plate. *Corythodinium*, *Oxytoxum*.

●●●●●● Centrodiniaceae Hernández-Becerril 2010

Alveolae containing thecal plates, forming a tabulation of 7 latitudinal series; one antapical plate. *Centrodinium*.

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●● Dinophysales Kofoid 1926
With a cingulum, a sulcus, and a sagittal suture extending the entire length of the cell, one ciliary pore. Apart from one possible fossil representative, only known from present day forms. *Amphisolenia*, *Citharistes*, *Dinofurcula*, *Dinophysis*, *Histioneis*, *Latifascia*, *Metadinophysis*, *Metaphalacroma*, *Ornithocercus*, *Oxyphysis*, *Parahistioneis*, *Phalacroma*, *Pseudophalacroma*, *Sinophysis*, *Triposolenia*.

●●●● Prorocentrales Lemmermann 1910
Without cingulum or sulcus; one ciliary pore; cilia apical—one wavy cilium clearly homologous with transverse cilium of other dinoflagellates and one not wavy; thecal plates. Fossils unknown. *Mesoporus*, *Prorocentrum*.

●● Apicomplexa Levine 1980, emend. Adl et al. 2005
At least one stage of the life cycle with flattened subpellicular vesicles and an apical complex consisting of one or more polar rings, rhoptries, micronemes, conoid and subpellicular microtubules; sexuality, where known, by syngamy followed by immediate meiosis to produce haploid progeny; asexual reproduction of haploid stages occurring by binary fission, endodyogeny, endopolyogeny and/or schizogony/merogony; locomotion by gliding, body flexion, longitudinal ridges and/or cilia; mostly parasitic.

*Incertae sedis* Apicomplexa: Agamococcidiorida Levine 1979
Merogony and gametogony both absent; several families described but position within Apicomplexa unclear. *Gemmocystis*, *Rhytidocystis*.

*Incertae sedis* Apicomplexa: Protococcidiorida Kheisin 1956
Merogony absent; extracellular gamogony and sporogony; in some species, gamogony and fertilization in the host, with oocysts released with sporogony in aqueous environment; sporozoites exist inside intestinal epithelium briefly, on their way to coelom or vascular tissues, where development occurs, followed by sporozoite release in the faeces. Subdivisions uncertain. *Angeiocystis*, *Coelotropha*, *Grellia*, *Eleutheroschizon*, *Mackinnonia*, *Myriosporides*, *Myriospora*, *Sawayella*.

*Incertae sedis* Apicomplexa: *Aggregata* Frenzel 1885—highly divergent 18S rRNA. *Christalloidophora* Dehorne, 1934—Merozoites with 2–4 fuchsinophile crystalloids. *Dobellia* Ikeda, 1914—Life cycle still confused, sporozoites invade intestinal epithelial cells, two forms of meronts: macromeront with period of intranuclear development, micromeront epicellular, syzygy of macro- and micromerozoites producing gametocysts, oocyst with 1000 naked sporozoites. *Echinococcidium* Porchet 1978—with single spines and spines arranged in bundles forming a pyramid on body surface, amylopectin granules, in large parasitoporous vacuole in intestinal epithelium or free in intestinal lumen. *Globidiellum* Brumpt 1913—intracellular in mononuclear leucocytes, endothelial cells and erythrocytes, formation of large number of merozoites. *Joyeuxella* Brasil 1902—Merogony in host epithelial cells. *Rhabdospora* Laguesse 1906—Meronts in host epithelial cells, merozoites with rodlets (rhoptries?). *Spermatobium* Eisen 1895—Young stages in sperm sac cells, later stages free in sperm sac, sporogonia (oocysts?), sporoblasts (sporocysts?) and residuum described. *Spiriopsis* Arvy and Peters 1972—with micronemes and paraglycon. *Spirogregarina* Wood and Herman 1943—Elongate, spindle-shaped, cylindrical, with spiral bands (grooves, epicytic folds?) on surface, bulbous, knob-like terminus at each end. *Toxocystis* Léger and Duboscq 1910—elongate, falciform with one broader end, nucleus with two paranuclear bodies opposite each other, not motile. *Trophosphaera* Le Calvez 1939—Spherical cysts with spherical cytomeres, cytomeres form spherical sporocytes (schizogony), sporocytes form eight naked spores.

●●● Aconoidasida Mehlhorn et al. 1980 [= Hematozoa Vivier 1982] (P)
Apical complex lacking conoid in asexual motile stages; some diploid motile zygotes (ookinetes) with conoid; macrogametes and microgametes forming independently; heteroxenous.

●●●● Haemosporoida Danilewsky 1885
Zygote motile as ookinete with conoid; ciliated microgametes produced by schizogonous process; oocyst formed in which sporozoites develop. *Dionisia*, *Haemocystidium*, *Haemoproteus*, *Hepatocystis*, *Leucocytozoon*, *Mesnilium*, *Nycteria*, *Para-haemoproteus*, *Plasmodium*, *Polychromophilus*, *Rayella*, *Sauropytozoon*.

●●●● Piroplasmorida Wenyon 1926
Piriform, round, rod-shaped or amoeboid; conoid and cilia absent in all stages; polar ring present; without oocyst; sexuality probably associated with the formation of large axopodium-like "Strahlen". *Anthemosoma*, *Babesia*, *Cytauxzoon*, *Echinozoon*, *Haemohormidium*, *Sauroplasma*, *Serpentoplasma*, *Theileria*.

●●●● Nephromycida Cavalier-Smith 1993, emend. Adl et al. 2019
Aciliate, motile infective stage (resembling sporozoites); spore-stage with rhoptry-like inclusions, biciliated stages exist; most of life cycle extracellular; symbionts/parasites of marine invertebrates (at least tunicates). *Nephromyces*, *Cardiosporidium*.

●●● Conoidasida Levine 1988 (P)
Complete apical complex, including a closed conoid in all or most asexual motile stages; cilia, where present, found exclusively in microgametes (male gametes); with the exception of microgametes, motility generally via gliding with possibility of body flexion

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

and undulation of longitudinal pellicular ridges; heteroxenous or homoxenous. This group is not monophyletic with subdivisions artificial and unclear at this time.

●●●●● Coccidia Leuckart 1879 (P)

Mature gametes develop intracellularly; microgamont typically produces numerous microgametes; syzygy absent; zygote rarely motile; sporocysts usually formed within oocysts.

●●●●●● Adeleorina Léger 1911

Microgamonts produce one to four microgametes, which associate with macrogamete in syzygy; endodyogony is absent. *Adelea*, *Adelina*, *Babesiosima*, *Bartazoon*, *Chagasella*, *Cyrilia*, *Dactylosoma*, *Desseria*, *Ganapatiella*, *Gibbsia*, *Hae-mogregarina*, *Haemolivia*, *Hepatozoon*, *Ithania*, *Karyolysus*, *Klossia*, *Klossiella*, *Legerella*, *Orcheobius*, *Rasajeyna*.

●●●●●●● Eimeriorina Léger 1911

Microgametes and macrogametes develop independently; syzygy is absent; microgamonts produce large number of ciliated microgametes; zygote is nonmotile; sporozoites always enclosed in sporocyst within oocyst. *Atoxoplasma, Bar-rouxia*, *Besnoitia, Caryospora, Caryotropha, Choleoeimeria, Cyclospora, Cystoisospora, Defretinella*, *Diaspora*, *Dor-isa*, *Dorisiella*, *Eimeria, Elleipsisoma*, *Goussia, Hammondia, Hyaloklossia, Isospora, Lankesterella, Mantonella*, *Merocystis, Neospora, Nephroisospora, Ovivora*, *Pfeifferinella, Pseudoklossia, Sarcocystis, Schellackia, Selenococcid-ium*, *Selysina*, *Spirocystis*, *Toxoplasma, Tyzzeria*, *Wenyonella*.

●●●●● Gregarinasina Dufour 1828 (P)

Mature gamonts usually develop extracellularly; syzygy of gamonts generally occurring with production of gametocyst; similar numbers of macrogametes and microgametes maturing from paired gamonts in syzygy within the gametocyst; syngamy of mature gametes leading to gametocyst that contains few to many oocysts, which each contain sporozoites; sporocysts absent; asexual reproduction (merogony) absent in some species.

*Incertae sedis* Gregarinasina: *Digyalum* Koura et al. 1990—only transverse epicytic folds, two pouches at anterior end; *Exoschizon* Hukui 1939—epicytic folds, schizogony at anterior end of trophozoite, cytoplasmic buds, 16 merozoites differentiated at anterior end of trophozoite.

●●●●●●● Archigregarinorida Grassé 1953 (P)

Trophozoite aseptate; with syzygy; encystment of gamonts; oocysts contain 4–8 or even more sporozoites. *Filipodium, Meroselenidium, Merogregarina, Platyproteum, Selenidium, Selenocystis, Veloxidium*.

●●●●●●●● Eugregarinorida Léger 1900 (P)

Trophozoite with epimerite in gregarines with septum or mucron in gregarines without septum; syzygy followed by encystment of gamonts; oocysts with 8 sporozoites. *Apolocystis*, *Amoebogregarina, Ancora, Ascogregarina, Asterophora, Blaberica, Caliculum, Cephaloidophora, Colepismatophila, Cystobia*, *Cystocephalus*, *Difficilina, Diplauxis*, *Enterocystis, Ganymedes, Geneiorhynchus, Gonospora, Gregarina, Heliospora, Hentschelia*, *Hirmocystis*, *Hoplorhynchus, Lankesteria, Lecudina, Lei-dyana, Lithocystis, Monocystella*, *Monocystis, Nematopsis, Nematocystis*, *Neoasterophora*, *Paralecudina, Paraschneideria, Phyllochaetopterus, Pileocephalus*, *Polyplicarium, Polyrhabdina, Porospora*, *Prismatospora, Protomagalhaensia, Psy-chodiella, Pterospora, Pyxinia, Pyxinioides, Rhabdocystis*, *Sphaerorhynchus*, *Steinina, Stenophora, Stylocephalus, Sycia*, *Syncystis, Thalicola*, *Thiriotia, Trichotokara, Uradiophora*, *Urospora, Xiphocephalus, Zygosoma* (examples).

●●●●●●● Neogregarinorida Grassé 1953

Trophozoite with epimerite or mucron; multiple rounds of schizogony/merogony; pairing of gamonts; oocysts contain eight sporozoites. *Apicystis, Aranciocystis, Caulleryella*, *Coelogregarina*, *Farinocystis*, *Gigaductus*, *Lipocystis*, *Lipo-tropha*, *Lymphotropha*, *Machadoella*, *Mattesia, Menzbieria, Ophryocystis, Schizocystis*, *Syncystis, Tipulocystis*.

●●●●●●●● Cryptogregarinorida Cavalier-Smith 2014, emend. Adl et al. 2019

Oocysts and meronts with attachment "feeder" organelle; anisogamous, microgametes aciliate; oocysts without sporozoites containing four naked sporozoites; epicellular localization in host cell. *Cryptosporidium*.

●●●●● Blastogregarinea Chatton and Villeneuve 1936, emend. Simdyanov et al. 2018

Permanent multinuclearity and gametogenesis: nuclear division of merogony and gamogony proceeds within the same individual (merogamont) throughout its life span; merogamonts motile and sexually differentiated. Female oogamy: continuous budding of macrogametes from the posterior part of female merogamonts. Male gamogony: budding of multinuclear

(continued)

<footnote n="35">³⁵The ordering of the major taxa follows the arrangement of most SSU rRNA phylogenies and recent phylogenomic analyses (e.g. Gentekaki et al., 2014). The current classification contains some polyphyletic or paraphyletic taxa marked by (P) which require further investigations (morphologic and/or genetic). Families are arranged alphabetically, unless phylogeny places a family at a higher hierarchical rank.</footnote>
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●● Ciliophora Doflein 1901 [Ciliata Perty 1852; Infusoria Bütschli 1887]</td><td>Cells with nuclear dimorphism, including a typically polygenomic macronucleus and at least one diploid micronucleus; somatic kinetids having a postciliary microtubular ribbon arising from triplet 9, a kinetodesmal fibril or striated rootlet homologue arising near triplets 5–8, and a transverse microtubular ribbon arising in the region of triplets 4–6; sexual reproduction, when present, by conjugation typically with mutual exchange of haploid gametic nuclei that fuse to form the synkaryon or zygotic nucleus.<sup>35</sup></td></tr><tr><td>●●● Postciliodesmatophora Gerassimova & Seravin 1976</td><td>Somatic dikinetids with postciliodesmata (overlapping postciliary microtubular ribbons separated by one or two microtubules).</td></tr><tr><td>●●●● Karyorelictea Corliss 1974</td><td>Two to many macronuclei containing approximately but sometimes slightly more than the diploid amount of DNA; macronuclei not dividing but replaced by division of micronuclei; major postciliary ribbons separated by two groups of microtubules.</td></tr><tr><td>●●●●● Kentrophoridae Jankowski 1980 (Kentrophoros)</td><td></td></tr><tr><td>●●●●●● Loxodida Jankowski 1980</td><td>Non-contractile; somatic cilia as files of dikinetids mainly on the right surface with the left surface non-ciliated, except for single marginal ('bristle') kinety; extrusomes as somatic cnidocyst-like organelles in some genera; oral kinetids as two dikinoidal perioral kineties and one intraoral (intrabuccal) kinety; stomatogenesis monoparakinetal or buccokinetal; nuclei in clusters, typically two macronuclei and one micronucleus; typically in anoxic sediments and anoxic waters.</td></tr><tr><td>●●●●●●● Cryptopharyngidae Jankowski 1980 (Cryptopharynx)</td><td></td></tr><tr><td>●●●●●●●● Loxodidae Bütschli 1889 (Loxodes)</td><td></td></tr><tr><td>●●●●● Geleiidae Kahl 1933 (Geleia)</td><td></td></tr><tr><td>●●●● Heterotrichea Stein 1859</td><td>Polygenomic macronucleus dividing by extra-macronuclear microtubules; major postciliary ribbons separated by one microtubule.</td></tr><tr><td>●●●●●●● Blepharismidae Jankowski in Small & Lynn 1985 (Blepharisma)</td><td></td></tr><tr><td>●●●●● Climacostomidae Repak 1972 (Climacostomum)</td><td></td></tr><tr><td>●●●●●● Condylostomatidae Kahl in Doflein & Reichenow 1929 (Chattonidium, Condylostoma)</td><td></td></tr><tr><td>●●●●● Fabreidae Shazib et al. 2014 (Fabrea)</td><td></td></tr><tr><td>●●●●●● Gruberiidae Shazib et al. 2014 (Gruberia)</td><td></td></tr><tr><td>●●●●●●● Coliphorina Jankowski 1967</td><td>With a node-based definition: the clade stemming from the most recent common ancestor of the Maristentoridae and Folliculinidae.</td></tr><tr><td>●●●●●●●● Folliculinidae Dons 1914 (Folliculina)</td><td></td></tr><tr><td>●●●●●●● Maristentoridae Miao et al. 2005 (Maristentor)</td><td></td></tr><tr><td>●●●●●● Peritromidae Stein 1867 (Peritromus)</td><td></td></tr><tr><td>●●●●●● Spirostomidae Stein 1867 (Anigsteinia, Spirostomum)</td><td></td></tr><tr><td>●●●●●●● Stentoridae Carus 1863 (Stentor)</td><td></td></tr><tr><td>●●● Intramacronucleata Lynn 1996</td><td>Polygenomic macronucleus dividing by intramacronuclear microtubules.</td></tr></tbody></table>

*Incertae sedis* Intramacronucleata: *Protocruzia* Faria da Cunha and Pinto 1922 [Protocruziidae Jankowski, 1980; Protocruziidia de Puytorac et al., 1987]

Nuclear apparatus a cluster of similar-sized nuclei with paradiploid macronuclei surrounding one or more micronuclei; each macronucleus possibly organized as a single composite chromosome. *Protocruzia*.

●●●● SAL Gentekaki et al. 2014
Group identified by phylogenomics. With a node-based definition: the clade stemming from the most recent common ancestor of the Spirotrichea (S) and Lamellicorticata (i.e. Armophorea (A) and Litostomatea (L)).

*Incertae sedis* SAL: *Cariacothrix* Orsi et al. 2012 [Cariacotrichea Orsi et al. 2011]
With archway-shaped kinety around oral opening and extending to posterior body end; with unique molecular signature 'GAAACAGUCGGGGUAUCAGUA' (spanning nucleotide positions 283-305 in GenBank accession number GU819615);

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

confirmed only from deep waters of anoxic Cariaco Basin, Venezuela. At least two adoral organelles; longitudinal ciliary rows; caudal cilia. *Cariacothrix caudata*.

*Incertae sedis* SAL: Mesodiniidae Jankowski, 1980

Somatic cilia bristle-like, of at least two types, arranged in girdles around the body; brosse kineties absent; extrusomes as oral toxicysts; oral region apical, domed, circular, and delimited by circumoral dikinetids, but apparently without nematodes-mata and bulge microtubules of rhabdos. *Mesodinium*.

*Incertae sedis* SAL: *Phacodinium* Prowazek 1900 [Phacodiniidia Small and Lynn 1985]

Somatic kineties as linear polykinetids; each kinetosome bearing a kinetodesmal fibril, and sometimes accompanied by a partner kinetosome in some regions of the body, thus resembling a cirrus. *Phacodinium*.

●●●●●● Spirotrichea Bütschli 1889

Conspicuous right and left oral and/or preoral ciliature; left serial oral polykinetids leading (usually clockwise) into the oral cavity, either around a broad anterior end or along anterior and left margins of the body; DNA replication in the macronucleus accomplished by a complicated migrating structure called replication band; extensive chromosomal fragmentation.

●●●●●●● Euplotia Jankowski 1979

Adoral zone usually with numerous polykinetids (paramembranelles); body dorsoventrally flattened; right preoral ciliature as paroral and/or endoral with diplo- or polystichomonad structure; somatic ciliature usually in dikinetidal rows on dorsal side and forming cirri on ventral side; somatic dikinetids with cilia at anterior basal bodies and retention of kinetodesmal fibrils; stomatogenesis generally apokinetal, sometimes hypoapokinetal or parakinetal; turn-over or replacement of only ventral somatic infraciliature; typically no resorption of all kinetosomes in cysts.

●●●●●●●● Euplotida Small & Lynn 1985

Hypoapokinetal stomatogenesis in subsurface tube.

●●●●●●●● Aspidiscidae Ehrenberg 1830 (Aspidisca)

●●●●●●●● Certesiidae Borror & Hill 1995 (Certesia)

●●●●●●●● Euplotidae Ehrenberg 1838 P (Euplotes)

●●●●●●●● Gastrocirrhidae Fauré-Fremiet 1961 (Gastrocirrhus)

●●●●●●●● Uronychidae Jankowski 1975 (Diophrys, Uronychia)

●●●●●●●●● Discocephalida Wicklow 1982

Left and right marginal rows form intrakinetally; epiapokinetal stomatogenesis; left most frontal cirrus originates from anterior end of undulating membrane-anlage; many frontoventral-transverse cirral anlagen; dorsal kinety anlagen formed in secondary mode; caudal cirri originate from rightmost dorsal kineties anlagen by multisegmentation mode; development of frontoventral-transverse cirral anlagen of primary type; migrating cirri are not formed, which are always derived from the right most cirral anlage in all traditional hypotrichs; anlage of undulating membranes splits transversely to form endoral and paroral membranes.

●●●●●●●●●● Discocephalidae Jankowski 1979 (Discocephalus, Prodiscocephalus, Paradiscocephalus)

●●●●●●●●●● Pseudoamphisiellidae Song et al. 1997 (Leptoamphisiella, Pseudoamphisiella)

●●●●●●●● Perilemmaphora Berger 2008

Perilemma present. Possibly, comprises also *Diophrys* and the discocephalids.

●●●●●●●●● Hypotrichia Stein 1859

Adoral zone usually with numerous polykinetids (paramembranelles) along anterior and left margins of dorsoventrally flattened body, rarely around broad apical end; right preoral ciliature as paroral and/or endoral, paroral diplo- or polystichomonad, endoral mono-, rarely diplostichomonad; somatic ciliature usually in dikinetidal rows on dorsal side and forming cirri on ventral side, rarely with jumping bristles instead of kineties and cirri; somatic dikinetids with cilia at anterior basal bodies and loss of kinetodesmal fibril; stomatogenesis epiapokinetal or parakinetal; complete turn-over or replacement of ventral and dorsal somatic ciliature; kinetosome-resorbing cysts.

●●●●●●●●●● Stichotrichida Fauré-Fremiet 1961 (P)

Ventral cirri as one or more longitudinal and linear (not zig-zag as in Urostylida) files or as frontoventral cirri, typically conspicuous, arranged in specific, localized frontal and ventral groups (i.e. sporadotrichs); dorsal ciliature typically regularly distributed in longitudinal files; stomatogenesis parakinetal or apokinetal, if apokinetal, may occur with five or six anlagen streaks in two groups for differentiation of ventral somatic ciliature (i.e. sporadotrichs). Note that this taxon is artificial. Many

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<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

*Incertae sedis* Choreotrichida: *Lynnella* Liu et al. 2011 [Lynnellidae Liu et al. 2011; Lynnellida Liu et al. 2015] (M)

Sistergroup relationship of this monotypic genus and order changes depending on the algorithms used in molecular approaches. Morphological and ontogenetic data suggest an affiliation with the aloricate choreotrichids: proximalmost collar membranelles elongated, extending into buccal cavity; two longitudinal somatic kineties both of which with distinctly derived kinetid structures: one is monokinetidal, the other composed of dikinetids with cilia only at the posterior basal bodies; endoral membrane extends across peristomial field in middle dividers; stomatogenesis in subsurface pouch; oral primordium parallel to cell surface; two macronuclear nodules. Adoral zone with (probably secondary) ventral gap. *Lynnella semiglobulosa*.

●●●●●●●●●● Strobilidiina Jankowski 1980 (P)

Adoral zone circular, rarely with secondary ventral gap; naked.

●●●●●●●●●●● Leegaardiellidae Lynn & Montagnes 1988 (Leegaardiella)

●●●●●●●●●●● Lohmanniellidae Montagnes & Lynn 1991 (Lohmanniella)

●●●●●●●●●●● Strobilidiidae Kahl in Doflein & Reichenow 1929 (Strobilidium)

●●●●●●●●●●● Strombidinopsidae Small & Lynn 1985 (Strombidinopsis) (P)

●●●●●●●●●●● Tintinnina Kofoid & Campbell 1929

Adoral zone circular; with hyaline, entirely or partially agglutinated lorica; somatic ciliature arranged in specialized fields and rows; frequently with extrusive capsules; with contractile peduncle. Molecular phylogenies contribute to far-reaching revision, but taxon coverage is insufficient, and tree topology is unsettled.

*Incertae sedis* Tintinnina: *Helicostomella*, *Tintinnopsis* (P), plus several further genera.

●●●●●●●●●●● Ascampbelliellidae Corliss 1960 (Ascampbelliella)

●●●●●●●●●●● Cyttarocylididae Kofoid and Campbell 1929 (Cyttarocylis)

(Probably, synonymous with Petalotrichidae)

●●●●●●●●●●● Dictyocystidae Haeckel 1873 (Dictyocysta)

●●●●●●●●●●● Epiplocylididae Kofoid & Campbell 1939 (Epiplocylis)

●●●●●●●●●●● Eutintinnidae Bachy et al. 2012 (Dartintinnus, Eutintinnus)

●●●●●●●●●●● Favellidae Kofoid & Campbell 1929 (Favella)

●●●●●●●●●●● Nolaclusiliidae Sniezek et al. 1991 (Nolaclusilis)

●●●●●●●●●●● Petalotrichidae Kofoid & Campbell 1929 (Petalotricha)

(Probably, synonymous with Cyttarocylididae)

●●●●●●●●●●● Ptychocylididae Kofoid & Campbell 1929 (Cymatocylis, Ptychocylis)

●●●●●●●●●●● Rhabdonellidae Kofoid & Campbell 1929 (Metacylis, Rhabdonella, Schmidingerella)

●●●●●●●●●●● Stenosemellidae Campbell 1954 (P) (Stenosemella)

●●●●●●●●●●● Tintinnidae Claparède & Lachmann 1858 (Amphorellopsis, Salpingacantha, Salpingella, Tintinnus)

●●●●●●●●●●● Tintinnidiidae Kofoid & Campbell 1929 (Tintinnidium)

●●●●●●●●●●● Undellidae Kofoid & Campbell 1929 (Undella)

●●●●●●●●●●● Xystonellidae Kofoid & Campbell 1929 (Dadayiella, Parafavella, Xystonella)

●●●●●●●●●●● L nicophoridae Bütschli 1887

Body hour-glass shaped, both ends discoidal; posterior disc adhesive, with peripheral rings of cilia anterior disc with serial oral polykinetids around oral region; ectosymbionts, temporarily attached to substrate or host by ciliated mobile, posterior adhesive disc. *L nicophora*, *Prolicnophora*.

●●●●●●●●●●● Kiitrichidae Nozawa 1941

With weakly differentiated and non-grouped somatic ature, i.e. cirri on ventral side generally uniform, no clearly defined marginal cirral rows, cirri mixed with dikinetids on dorsal side, i.e. no clearly differentiated dorsal kineties. *Caryotricha*, *Kiitricha*.

●●●●●●●●●●● Lamelicorticata Vd'ačný et al. 2010

Postciliary microtubular ribbons arranged in a single layer right of and between kineties; oral apparatus composed of a

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

dikinetidal paroral membrane and several multirowed adoral membranelles; somatic dikinetids typically very narrowly spaced in anterior body portion; stomatogenesis telokinetal, commencing in dorsal or dorsolateral somatic kineties, and with migrating oral kinetofragments.

●●●●●● Armophorea Lynn 2004 (R)

Somatic dikinetids; energy-generating organelles as anaerobic mitochondria or hydrogenosomes; contain cytoplasmic endosymbiotic methanogenic bacteria; extensive chromosomal fragmentation; stomatogenesis typically pleurokinetal; in oxygen-depleted habitats.

*Incertae sedis* Armophorea: *Mylestomatidae* Kahl in Doflein & Reichenow, 1929 (*Mylestoma*)

●●●●●●● Metopida Jankowski 1980 (P)

Free-living or endocommensal Armophorea with five or fewer perizonal stripe kineties.

●●●●●●●● Metopidae Kahl 1927 (P)

Anterior part of body uniquely twisted to the left; with series of five perizonal somatic kineties.
*Bothrostoma*, *Brachonella*, *Eometopus*, *Metopus*, *Parametopidium*, *Tesnospira*.

●●●●●●●● Apometopidae Foissner 2016

Obpyriform to clavate Metopida with perizonal ciliary stripe composed of four kineties. *Cirranter*, *Urostomides*.

●●●●●●●●● Tropidoatractidae Rotterová et al. 2018

Preoral dome flattened, without torsion; cortex with interkinetal ridges; sparse, widely spaced somatic ciliature; short peristomium with deep, cup-like buccal cavity; adoral zone reduced, more or less straight; perizonal stripe with five rows arranged in false kineties. *Palmarella*, *Tropidoattractus*

●●●●●●●● Clevelandida de Puytorac & Grain 1976

Body typically flattened; somatic dikinetids with non-microtubular retrodesmal and cathetodesmal fibrils; oral polyketinets with a fourth row of kinetosomes directly opposite those of the third (heteromembranelles); paroral as diplostichomonad; macronucleus anchored in a karyophore in many species; conjugation often synchronized with reproductive life cycle of the host; endocommensals in digestive tracts of invertebrates and some vertebrates.

●●●●●●●● Clevelandidae Kidder 1938 (Clevelandella)

●●●●●●●● Inferostomatidae Ky 1971 (Inferostoma)

●●●●●●●● Neonyctotheridae Affa'a 1987 (Neonyctotherus)

●●●●●●●● Nyctotheridae Amaro 1972 (P) (Nyctotherus)

●●●●●●●● Sicuophoridae Amaro 1972 (Sicuophora)

●●●●●●●● Caenomorphidae Poche 1913

Body globular or conical, rigid, twisted to the left; somatic cilia as small kineties or cirrus-like tufts; several oral polyketinets in small oral cavity in posterior cell half; paroral possibly absent; free-swimming. Complex perizonal ciliary stripe comprising more than five kineties. Small subunit ribosomal DNA analysis suggests a sister group relationship with the *Litostomatea*. *Caenomorpha*, *Ludio*, *Sulfonecta*.

●●●●●●●● Odontostomatida Sawaya 1940

Discoid, laterally compressed, wedge- or helmet-shaped, typically nearly as wide as long, with armour-like cuirass and often short posterior spines; somatic cilia arising from cortical pits; oral polyketinets inconspicuous, typically less than ten in number.

●●●●●●●● Discomorphellidae Corliss 1960 (Discomorphella)

●●●●●●●● Epalxellidae Corliss 1960 (Epalxella, Saprodinium)

Note that *Epalxella* has been genetically characterized with Plagiopylea but *Saprodinium* with *Armophorea*.

●●●●●● Litostomatea Small & Lynn 1981

Somatic monokinetids with two transverse ribbons, a slightly convergent postciliary ribbon, and a laterally directed kinetodesmal fibril that does not overlap those of adjacent kineties; one tangential transverse extending anteriorly into the somatic ridge to the left of the kinetid, one radial transverse ribbon extending transversely into the adjacent somatic ridge; one to several dorsal somatic kineties differentiated as brosse or brush kineties with specialized dikinetids bearing clavate *cilia lamina corticalis* or ecto-endoplasmic fibrillar layer often present and well-developed; oral ciliature as simple kinetids from which nematodesmata arise, supporting the cytopharynx, but

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

nematodesmata may also arise from "oralized" somatic kinetids adjacent to the oral region; stomatogenesis telokinetal.

Rhynchostomatia Jankowski 1980

Elongate to flask-shaped body with dorsal proboscis of varying relative length; oral region circular or elliptical, possibly with permanent cytostome, distant from extreme anterior end of body, i.e. at base of the proboscis, but with right branch of circumoral kinety accompanied by at least one perioral kinety, extending along one border of the ventral surface of the proboscis, and with left branch of circumoral kinety accompanied by many oblique preoral kineties along the other border; toxicysts in the ventral band of the proboscis or distributed around the cytostome.

Dileptida Jankowski 1978

With a hybrid circumoral kinety; a staggered dorsal brush; and a stripe without cilia on the left side of the proboscis.

Dileptidae Jankowski 1980 (Apodileptus, Dileptus, Pseudomonilicaryon)

Dimacrocaryonidae Jankowski 1978 (Dimacrocaryon, Monomacrocaryon, Rimaleptus)

Trachelidae Ehrenberg 1838

Body broad ovoid; proboscis immobile or only slightly mobile, with dorsal side distinctly shorter than ventral one; distinct groove (fossa) on right side containing and surrounded by condensed somatic ciliature; dorsal brush three- to four-rowed and isoarchistichad; circumoral kinety dikinetidal throughout; internal oral basket clavate. *Trachelius*.

Haptoria Corliss 1974 (P)

Oral region typically circular or elliptical, with circumoral dikinetids whose microtubules support the cytostome-cytopharynx; where circumoral dikinetids are absent, oralized somatic monokinetids bear nematodesmata forming the rhabdos; anterior condensation of dikinetidal cilia forming a dorsal brush, partially reduced; somatic kinetids otherwise monokinetidal after loss of anterior basal body; toxicysts; predatory life style. Questionable support for its monophyly as several members group with Trichostomatia, and its genera *Helicoprorodon* and/or *Trachelotactus* branch basally in the class *Litostomatea*.

*Incertae sedis* Haptoria: *Chaenea*.

Lacrymariidae de Fromentel 1876

Anterior region of the body (=head) bulb-like, covered by short oblique kineties with densely packed kinetids that abut the circumoral dikinetids. *Lacrymaria*.

Haptorida Corliss 1974

Oral region typically circular or elliptical, surrounded by circumoral dikinetids whose microtubules extend to support the cytostome-cytopharynx; where circumoral dikinetids are absent, oralized somatic monokinetids bear nematodesmata forming the rhabdos.

Enchelyodonidae Foissner et al. 2002 (Enchelyodon, Fuscheria)

Homalozoonidae Jankowski 1980 (Homalozoon)

Pleurolitidae Foissner 1996 (Pleurolites)

Didiniidae Poche 1913

Somatic cilia as series of apparently short kinetofragments in one or more girdles around body, but in non-ciliated regions, non-ciliated kinetosomes are arranged in meridional kineties; brosse typically a field of clavate cilia or "sensory bristles" usually clearly detectable in 3-5 kineties. *Didinium, Monodinium*.

Pleurostomatida Schewiakoff 1896

Body leaf-like or laterally compressed; free-swimming, typically gliding on the substrate; somatic cilia tion on both body sides, typically more dense on the right side; brosse dorsal, integrated in one or two dorsolateral kineties; oral region ventral and elongated, with oral kinetids as left and right components extending along the ventral edge of the laterally flattened body, bordering a slit-like cytostome, sur rounded by toxicysts; micronucleus lying between two macronuclear nodules; voracious cytotrophs.

Amphileptidae Bütschli 1889 (Amphileptus)

Litonotidae Kent 1882 (Litonotus)

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

Pseudochlamydonellidae Buitkamp et al. 1989 (Hackenbergia, Pseudochlamydonella)
Marynidae Poche 1913 (Maryna)

●●●●●●●● Bryophryina de Puytorac et al. 1979

Oral cavity almost flat; right oral field a single row of dikinetids or a complex organelle including roof kineties; left field as described for order; silverline pattern platyphryid or colpodid; division in reproductive cysts; terrestrial.

●●●●●●●●● Bryophryidae de Puytorac et al. 1979 (Bryophrya)

●●●●●●●●● Sandmanniellidae Foissner & Stoeck 2009 (Sandmanniella)

●●●●●●●● Colpodina Foissner et al. 2011

Oral cavity small to very large, in the latter case densely ciliated by roof kineties having supra-epiplasmic micro-tubules; right oral field composed of a dikinetidal row and a crescentic accumulation of slightly disordered mono-kinetids; left oral field as a crescentic polykinetid composed of many monokinetidal rows; postorally, a more or less pronounced (diagonal) groove extending obliquely onto left body side; extrusomes globular or oblong; silver-line pattern colpodid; division usually in reproductive cysts; stomatogenesis pleurootelokinetal; terrestrial and limnetic.

●●●●●●●●● Colpodidae Bory de St. Vincent 1826 (P) (Colpoda)

●●●●●●●●● Grandoriidae Corliss 1960 (Grandoria)

●●●●●●●●● Tillinidae Foissner et al. 2011 (Tillina)

●●●●●●●●● Grossglockneriidae Foissner 1980 [Grossglockneriina Foissner 1980]

Oral apparatus on cell surface; with unique feeding tube used for puncturing cell walls of fungi and yeasts; right oral field as single monokinetidal row; left oral field composed of one to several brick-shaped polykinetids; silver-line pattern colpodid; division in reproductive cysts; stomatogenesis merotelokinetal; terrestrial. *Grossglockneria, Pseudoplatyophrya*.

●●●●●●●● Cyrtolophosidida Foissner 1978

Oral cavity shallow; right oral field as a single dikinetidal row, forms an elliptical figure with left oral field comprising up to 10 brick-shaped polykinetids; occasionally micronucleus in perinuclear space of macronucleus; silverline pattern colpodid or kreyellid; division in freely motile condition; stomatogenesis pleurotelokinetal, parental oral ciliature partially reorganized; limnetic and terrestrial, some marine.

●●●●●●●●● Cyrtolophosididae Stokes 1888 (Cyrtolophosis)

●●●●●●●●● Kreyellidae Foissner 1979 (Kreyella)

●●●●●●●● Platyophryida de Puytorac et al. 1979

Oral structures on cell surface; right oral field as a single dikinetidal row, usually forms an elliptical figure with the left oral field composed of few to many brick-shaped polykinetids; occasionally micronucleus in perinuclear space of macronucleus; some with postoral pseudomembrane consisting of short kineties with two dikinetids each along left slope of oral aperture; silverline pattern platyphryid, rarely colpodid or kreyellid; division in reproductive cysts or in freely motile condition; stomatogenesis pleurotelokinetal, parental oral ciliature not reorganized; with or without the ability to form aerial sorocarps; mostly terrestrial or semiterrestrial, few limnetic.

●●●●●●●● Ottowphryidae Foissner et al. 2011 (Ottowphrya, Platyophryides)

●●●●●●●●● Platyophryidae de Puytorac et al. 1979 (P) (Platyophrya)

●●●●●●●● Sagittariidae Grandori & Grandori 1935 (Sagittaria)

●●●●●●●●● Sorogenidae Bradbury & Olive 1980 (Sorogena)

●●●●●●●●● Woodruffiidae Gelei 1954 (Etoschophrya, Rostrophrya, Woodruffia)

●●●●●● Nassophorea Small & Lynn 1981 (P)

Somatic cilia as monokinetids and dikinetids; monokinetid with an anterior, tangential transverse ribbon, a divergent postciliary ribbon, and an anteriorly directed kinetodesmal fibril; somatic alveoli well-developed with paired alveolocysts sometimes present; oral nematodesmata well-developed as cyrtos in several groups.

●●●●●●●● Colpodidiidae Foissner 1995

Oral region in middle third of cell, with a paroral and three oral polykinetids that can be reduced in size to only one or two kinetosomes; cytostome-cytopharynx supported by a delicate cyrtos (?), which extends anteriorly, then dorsally and posteriorly. *Colpodidium*.

●●●●●●●● Nassulida Jankowski 1967

Alveolocysts present; somatic ciliature with distinct preoral suture; somatic basal bodies with a proximal and distal

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

cartwheel; somatic extrusomes rod-shaped when present; synhymenium or hypostomial frange begins in postoral region, always to the right of the stomatogenic kinety, and extending to lateral left onto dorsal surface, but sometimes reduced to three or four polykinetids restricted to a shallow oral cavity; cyrtos typically large, with complete palisade of nematodesmata.

●●●●●●● Furgasoniidae Corliss 1979 (Furgasonia, Wolfkosia)

●●●●●●● Nassulidae de Fromentel 1874 (Nassula, Obertrumia)

●●●●●● Microthoracida Jankowski 1967

Body frequently broadly ellipsoidal with right side more rounded, occasionally crescentic, and often laterally flattened; alveolocysts present; pellicle, firm and rigid, with thickened epiplasm in some forms; typically with a few somatic kinetids, separated by wide interkinetal spaces, composed of monokinetids and/or dikinetids; somatic extrusomes as fibrous trichocysts with anchor-shaped tip (fibrocysts); usually three left oral polykinetids; right paroral field of dikinetids variably developed, but its vestige always appears during stomatogenesis; cyrtos small, with complete palisade of nematodesmata.

●●●●●●● Microthoracidae Wrzesniowski 1870 (Drepanomonas, Microthorax)

●●●●●● Leptopharyngidae Kahl 1926 (Leptopharynx, Pseudomicrothorax)

●●●●● Prostomatea Schewiakoff 1896 (P)

Oral dikinetids radial to tangential to perimeter of oral area with postciliary microtubular ribbons extending laterally from each dikinetid, overlapping one another, and, in some species, forming a circular microtubular band that supports the wall of a shallow precytostomial cavity; associated oral ciliature as two or more assemblages of dikinetids, often called a "brush".

●●●●●● Apsiktratidae Foissner et al. 1994 [Prostomatida Schewiakoff, 1896]

Somatic ciliature "radially symmetrical"; paratenes typically conspicuous; oral region apical, surrounded by circumoral dikinetids; brosse absent; toxicysts absent. *Apsiktrata*.

●●●●●● Prorodontida Corliss 1974

Alveoli well-developed, including calcium carbonate concretions as skeletal plates in the Family Colepidae; somatic ciliation may be reduced in posterior half of cell, which typically bears one to many caudal cilia somatic extrusomes as mucocysts; oral extrusomes as toxicysts, may be in oral palps or extra-oral, near kinetids of "brosse"; oral region apical to subapical, surrounded by circumoral dikinetids; brosse typically of three or more dikinetidal rows bearing clavate cilia varying from parallel to perpendicular to body axis, and developing on parental ventral surface; cytostome sometimes in shallow atrium, which is lined by oral ridges supported by two unequal rows of microtubules; most species cytrotrophic or scavengers on detritus.

●●●●●●● Balanionidae Small & Lynn 1985 (Balanion)

●●●●●●● Cryptocaryonidae Wright & Colorni 2002 (Cryptocaryon)

●●●●●●● Colepidae Ehrenberg 1838 (Coleps, Plagiopogon)

●●●●●●● Holophryidae Perty 1852 (Holophrya)

●●●●●●● Lagynidae Sola et al. 1990 (Lagynus)

●●●●●●● Metacystidae Kahl 1926 (Metacystis, Vasicola)

●●●●●●● Placidae Small & Lynn 1985 (Placus)

●●●●●●● Plagiocampidae Kahl 1926 (Plagiocampa)

●●●●●●● Prorodontidae Kent 1881 (Prorodon)

●●●●●●● Urotrichidae Small & Lynn 1985 (Urotricha)

●●●●● Plagiopylea Small & Lynn 1985 (R)

Alveoli well-developed, often filled with dense material; somatic monokinetid with divergent postciliary ribbon, well-developed anteriorly directed kinetodesmal fibril, and a transverse ribbon arising from dense material near triplets 2 and 3, but if *Epalxella* is correctly placed here, they typically have dikinetids; somatic extrusomes as mucocysts; cytostome partially encircled by one or two files of dikinetids, but if *Epalxella* is correctly placed here, oral ciliature can include polykinetids; stomatogenesis holotelokinetal, but may be apokinal in *Epalxella*; mitochondria may be replaced by hydrogenosomes, which in many species are associated with endosymbiotic methanogens.

●●●●●● Plagiopylida Small & Lynn 1985

Typically with sandwich-like arrangement of the hydrogenosome-methanogen assemblages.

●●●●●●● Epalxellidae Corliss 1960

Morphology suggests an affiliation with the Odontostomatida, while SSU rRNA phylogenies indicate a

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●●●●● Tetrahymenida Fauré-Fremiet in Corliss 1956
Somatic kinetids with anteriormost kinetid as a dikinetid; oral region, inconspicuous, except in species that undergo microstome-to-macrostome transformation; oral structures with right oral *b* segment of paroral (haplokinety, undulating membrane) and three left oral polykinetids (membranelles) in oral cavity; stomatogenesis monoparakinetal, typically involving the rightmost postoral somatic kinety; microphagous forms primarily bacterivorous, but some histophagous and several polymorphic forms with cytotrophic macrostome stage; complex life cycle in histophagous and parasitic species; in freshwater habitats, sometimes terrestrial, and others as facultative or obligate parasites associated mainly with invertebrate hosts.

*Incertae sedis* Tetrahymenida: Trichospiridae Kahl, 1926 (*Trichospira*)

●●●●●●●●● Curimostomatidae Jankowski 1968 (*Curimostoma*)
●●●●●●●●● Glaucomidae Corliss 1971 (*Glaucoma*)
●●●●●●●●● Spirozonidae Kahl 1926 (*Spirozona*)
●●●●●●●●● Tetrahymenidae Corliss 1952 (*Tetrahymena*)
●●●●●●●●● Turaniellidae Didier 1971 (*Colpidium, Dexiostoma, Turaniella*)

●●●●●●●● Ophryoglenida Canella 1964
Somatic ciliature very dense, with preoral suture; oral region inconspicuous, with paroral and three oral polykinetids, its wall "supported" by the organelle of Lieberkühn in at least one stage of the life cycle: stomatogenesis teloparakinetal, with dedifferentiation and replacement of parental oral structures, accompanied by marked regression of the paroral in the differentiated oral apparatus; division free-swimming or by palintomy in a cyst; histophagous forms generally feeding on moribund or wounded invertebrates, though several species attack healthy fishes; in freshwater habitats; polymorphic life cycle, including resting cysts.

●●●●●●●●● Ichthyophthiriidae Kent 1881 (*Ichthyophthirius*)
●●●●●●●●● Ophryoglenidae Kent 1881 (*Ophryoglena*)

●●●●●●●● Peniculia Fauré-Fremiet in Corliss 1956 (P)
Somatic kinetids with tangential transverse ribbons and prominently overlapping kinetodesmal fibrils; cortical alveoli lie between kinetosomal rows of oral polykinetids; extrusomes as typical fibrous trichocysts.

●●●●●●●● Peniculida Fauré-Fremiet in Corliss 1956
Somatic kinetids predominantly dikinetids; somatic extrusomes as trichocysts.

●●●●●●●●● Clathrostomatidae Kahl 1926 (*Clathrostoma*)
●●●●●●●●● Frontoniidae Kahl 1926 (*Disematostoma, Frontonia* (P))
●●●●●●●●● Lembadionidae Jankowski in Corliss 1979 (*Lembadion*)
●●●●●●●●● Maritujidae Jankowski in Small & Lynn 1985 (*Marituja*)
●●●●●●●●● Neobursaridiidae Dragesco & Tuffrau 1967 (*Neobursaridium*)
●●●●●●●●● Parameciidae Dujardin 1840 (*Paramecium*)
●●●●●●●●● Paranassulidae Fauré-Fremiet 1962 (*Paranassula*)
●●●●●●●●● Stokesiidae Roque 1961 (*Stokesia*)

●●●●●●●● Urocentridae Claparède & Lachmann, 1858 [Urocentrida de Puytorac, Grain & Mignot 1987]
Body broadly cylindrical with larger, rounded anterior half; free-swimming, but may be temporarily attached to the substratum by a mucous thread; somatic ciliation as a distinct equatorial girdle; caudal cilia form a conspicuous tuft that is used for temporary attachment to substrates by a mucous thread; somatic kinetids only as monokinetids with broad, tangential transverse ribbon; somatic extrusomes as mucocysts; oral structures as a paroral along the right margin of the oral opening and three oral polykinetids of three rows each along the dorsal-left wall. *Urocentrum*.

●●●●●●●● Peritrichia Stein 1859
Body divided into three major areas: (1) oral, with a prominent peristome bordered by a dikinetid file (haplokinety) and an oral polykinetid that both originate in an oral cavity (infundibulum) at the base of which is the cytostome; (2) aboral, including kinetosomes as part of the scopula, which secretes the stalk of sessile species; and (3) telotroch, permanently ciliated on mobile species.

●●●●●●●● Sessilida Kahl 1933
Body inverted bell- or goblet-shaped or conical-cylindrical; zooids dimorphic, with mature zooids or trophonts, sedentary or sessile, commonly stalked or with inconspicuous adhesive disc, attached to substrate by scopula, but a few species presumed to be secondarily mobile; dispersal stage as migratory telotroch; division isotomic

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

or anisotomic, followed in many species by development into arboroid colonies; resting cysts; free-living or ectosymbionts, rarely endosymbionts.

<table><tr><td>●●●●●●●●</td><td>Astylozoidae Kahl 1935 (Astylozoon, Hastatella)</td></tr><tr><td>●●●●●●●●</td><td>Ellobiophryidae Chatton and Lwoff 1929 (Ellobiophrya)</td></tr><tr><td>●●●●●●●●</td><td>Epistylididae Kahl 1933 (Epistylis)</td></tr><tr><td>●●●●●●●●</td><td>Lagenophryidae Bütschli 1889 (Lagenophrys)</td></tr><tr><td>●●●●●●●●</td><td>Operculariidae Fauré-Fremiet in Corliss 1979 (Opercularia)</td></tr><tr><td>●●●●●●●●</td><td>Rovinjellidae Matthes 1972 (Rovinjella)</td></tr><tr><td>●●●●●●●●</td><td>Scyphidiidae Kahl 1933 (P) (Scyphidia)</td></tr><tr><td>●●●●●●●●</td><td>Termitophryidae Lom in Corliss 1979 (Termitophrya)</td></tr><tr><td>●●●●●●●●</td><td>Usconophryidae Clamp 1991 (Usconophrys)</td></tr><tr><td>●●●●●●●●</td><td>Vaginicolidae de Fromentel 1874 (Cothurnia, Pyxicola, Thuricola, Vaginicola)</td></tr><tr><td>●●●●●●●●</td><td>Vorticellidae Ehrenberg 1838 (Carchesium, Epicarchesium (P), Ophrydium, Pelagovorticella, Pseudovorticella (P), Vorticella (P))</td></tr><tr><td>●●●●●●●●</td><td>Zoothamniidae Sommer 1951 (Haplocaulus, Zoothamnium)</td></tr></table>

●●●●●●●● Mobilida Kahl 1933

Body conical, cylindrical, or goblet-shaped, sometimes discoidal and orally aborally flattened; zooid mobile, with permanently ciliated trochal band, typically composed of three rings of cilia; adhesive disc on aboral pole, slightly contractile; with a ring-like, complex skeletal armature of denticles and fibres surrounding a vestigial scopula; oral region not contractile; oral structures with infundibular portions of oral polykinetids 1 and 2 always running together in a "ribbon" and oral polykinetid 3 short, perpendicular to the other two oral polykinetids; bacterivorous, obtaining prey from water or from detritus adhering to the host, and microphagous on cellular debris from host; ectosymbionts, often on the integument or gills of invertebrates, rarely endosymbionts.

<table><tr><td>●●●●●●●●</td><td>Polycyclidae Poljansky 1951 (Polycycla)</td></tr><tr><td>●●●●●●●●</td><td>Trichodinidae Claus 1874 (Trichodina)</td></tr><tr><td>●●●●●●●●</td><td>Trichodinopsidae Kent 1881 (Trichodinopsis)</td></tr><tr><td>●●●●●●●●</td><td>Urceolariidae Dujardin 1840 (Leiotrocha, Urceolaria)</td></tr></table>

●●●●●●●● Scuticociliatia Small 1967 (P)

Paroral file of dikinetids with *a*, *b*, and *c* segments; stomatogenesis by proliferation of kinetosomes from the *c* segment or a "scutico"-vestige posterior to *a* and *b* segments, with varying involvement of kinetosomes in the *a* and *b* segments; typically three oral polykinetids, often as membranoids; somatic dikinetids usually with both basal bodies ciliated; mucocysts; mitochondria cortically located, often-fused to chondriome; stomatogenesis scuticobuc-cokinetal.

●●●●●●●● Philasterida Small 1967

Paroral file of dikinetid shorter than other oral structures, typically by reduction of paroral *a* and *c* segments; scutica typically present.

<table><tr><td>●●●●●●●●</td><td>Cohnilembidae Kahl 1933 (Cohnilembus)</td></tr><tr><td>●●●●●●●●</td><td>Cryptochilidae Berger in Corliss 1979 (Cryptochilum.)</td></tr><tr><td>●●●●●●●●</td><td>Entodiscidae Jankowski 1973 (Entodiscus)</td></tr><tr><td>●●●●●●●●</td><td>Entorhipidiidae Madsen 1931 (Entorhipidium)</td></tr><tr><td>●●●●●●●●</td><td>Orchitophryidae Cépède 1910 (P) (Orchitophrya)</td></tr><tr><td>●●●●●●●●</td><td>Paralembidae Corliss & de Puytorac in Small & Lynn 1985 (Anophrys, Paralembus)</td></tr><tr><td>●●●●●●●●</td><td>Parauronematidae Small & Lynn 1985 (Parauronema (P)) (P)</td></tr><tr><td>●●●●●●●●</td><td>Philasteridae Kahl 1931 (Kahlilembus, Philaster)</td></tr><tr><td>●●●●●●●●</td><td>Pseudocohnilembidae Evans & Thompson 1964 (Pseudocohnilembus)</td></tr><tr><td>●●●●●●●●</td><td>Schizocaryidae Jankowski 1979 (Schizocaryum)</td></tr><tr><td>●●●●●●●●</td><td>Thigmophryidae Chatton & Lwoff 1926 (Thigmophrya)</td></tr><tr><td>●●●●●●●●</td><td>Thyrophylacidae Berger in Corliss 1961 (Thyrophylax)</td></tr><tr><td>●●●●●●●●</td><td>Uronematidae Thompson 1964 (Uronema)</td></tr><tr><td>●●●●●●●●</td><td>Urozonidae Grolière 1975 (Urozona)</td></tr></table>

●●●●●●●● Pleuronematida Fauré-Fremiet in Corliss 1956

Paroral often prominent forming a velum, with short *a* and elongate *b* segment and with *c* segment as a permanent scutica or scuticovestige; mucocysts; stomatogenesis from proter's paroral and scutica.

<table><tr><td>●●●●●●●●</td><td>Calyptotrichidae Small & Lynn 1985 (Calyptotricha)</td></tr></table>

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><tr><td>●●●●●●●●</td><td>Conchophthiridae Kahl in Doflein and Reichenow 1929 (Conchophthirus)</td></tr><tr><td>●●●●●●●●</td><td>Ctedoctematidae Small &amp; Lynn 1985 (Ctedoctema)</td></tr><tr><td>●●●●●●●●</td><td>Cyclidiidae Ehrenberg 1838 (P) (Cristigera, Cyclidium)</td></tr><tr><td>●●●●●●●●</td><td>Dragescoidae Jankowski 1980 (Dragescoa)</td></tr><tr><td>●●●●●●●●</td><td>Eurystomatellidae Miao et al. 2010 (Eurystomatella)</td></tr><tr><td>●●●●●●●●</td><td>Histiobalantiidae de Puytorac &amp; Corliss in Corliss 1979 (Histiobalantium)</td></tr><tr><td>●●●●●●●●</td><td>Peniculistomatidae Fenchel 1965 (Peniculistoma)</td></tr><tr><td>●●●●●●●●</td><td>Pleuronematidae Kent 1881 (P) (Pleuronema)</td></tr><tr><td>●●●●●●●●</td><td>Thigmocomidae Kazubski 1958 (Thigmocoma)</td></tr></table>

●●●●●●●● Thigmotrichida Chatton & Lstoff 1922

Thigmotactic cilia as anterior differentiations of somatic kineties, attach to host tissues; somatic kineties often spiralled around posterior cell pole, where cytostome is located; paroral not velum-like; oral polykinetid 3 reduced or absent; stomatogenesis from proter's paroral and scutica. In molecular analyses, often nested within the Pleuronomatida close to the cyclidiids.

<table><tr><td>●●●●●●●●</td><td>Ancistridae Issel 1903 (Ancistrum)</td></tr><tr><td>●●●●●●●●</td><td>Hemispeiridae König 1894 (Hemispeira)</td></tr><tr><td>●●●●●●●●</td><td>Hysterocinetidae Diesing 1866 (Hysterocineta)</td></tr><tr><td>●●●●●●●●</td><td>Paraptychostomidae Ngassam et al. 1994 (Paraptychostomum)</td></tr></table>

●●●●●●●● Loxocephalida Jankowski 1964 (P)

Non-monophyletic group that is most closely related to Astomatia and Apostomatia; further studies are needed in order to clarify the systematics of the loxocephalids.

<table><tr><td>●●●●●●●●</td><td>Cinetochilidae Perty 1852 (P) (Cinetochilum, Sathrophilus)</td></tr><tr><td>●●●●●●●●</td><td>Loxocephalidae Jankowski 1964 (Cardiostomatella, Dexiotricha, Loxocephalus)</td></tr></table>

● Rhizaria Cavalier-Smith 2002

With fine pseudopodia varying as simple, branching, or anastomosing patterns, often supported by microtubules in those groups examined by electron microscopy.

*Incertae sedis* Rhizaria: Gymnosphaerida Poche 1913, emend. Mikrjukov 2000

Axopodial microtubules in irregular hexagonal prism; kinetocyst and other types of extrusomes along axopodia; tubular mitochondrial cristae; in some genera, cells attached to substrate with cytoplasmic stalk; free-swimming as amoeboid or motile biciliated cells; one or more nuclei, often located in the amoeboid base of stalk when present; complex life cycle unresolved. *Actinocoryne*, *Cienkowskya*, *Gymnosphaera*, *Hedraiphrys*\* (possible junior synonym of Cienkowskya), *Wagnerella*\*. Note: This group is placed here based solely on morphology, as there is no DNA sequence information.

●● Cercozoa Cavalier-Smith 1998, emend. Adl et al. 2005; emend. Cavalier-Smith 2018

Diverse clade lacking distinctive morphological or behavioural characters; biciliated and/or amoeboid, usually with filopodia; most with tubular mitochondrial cristae; cysts common; kinetosomes connecting to nucleus with cytoskeleton; usually with microbodies and extrusomes.

*Incertae sedis* Cercozoa: Discocelia Cavalier-Smith 2013 [*Discocelis* Vørs 1988].

*Incertae sedis* Cercozoa: Psammonobiotidae\* Golemansky 1974, emend Meisterfeld 2002

This clade is considered as most likely belonging to Euglyphida. However, this position remains to be confirmed as they do not secrete scales. Test resembling a Greek vase with terminal collar either straight or angled, test circular in cross-section with aboral end spherical, flattened or pointed; mostly in marine interstitial sand, but also in freshwater and soils. Including *Alepiella*, *Chardezia*, *Edaphonobiotus*, *Feuerbornia*, *Frenzelina*, *Lesquerella*, *Micramphora*, *Micropsammella*, *Nadinella*, *Ogdeniella*, *Psammonobiotus*, *Propsammonobiotus* and *Rhumbleriella*.

*Incertae sedis* Cercozoa: Volutellidae Sudzuki 1979

Test half-coiled, either totally organic or with some attached particles; marine. *Pseudovolutella*, *Volutella*.

*Incertae sedis* Cercozoa: Kraken Dumack, Schuster, Bass et Bonkowski 2016

Very slow moving filose amoeboid cell, roundish in shape; usually a single highly branched filopodium originating between the cell body and the substrate through a ring-like structure sometimes visible by light microscopy; filopodium branching and anastomoses forming a network; cell division longitudinal; phagocytosis of bacteria, prey transported through the filopodium to the cell body; with one, rarely two, nuclei with a round nucleolus, one contractile vacuole, and usually one food vacuole.

*Incertae sedis* Cercozoa: Dictiomyxa, Katabia, Myxodictyium, Pontomyxa, Protomyxa, Protogenes, Pseudospora, Rhizoplasma.

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●● Cercomonadida Poche 1913, emend. Vickerman 1983, emend. Mylnikov 1986, emend. Karpov et al. 2006; emend Howe et al. 2009; emend Cavalier-Smith 2012; [=Cercomonadidae Kent 1880, emend. Mylnikov and Karpov 2004; Cercobodonidae Hollande 1942].

Phagotrophic and heterotrophic biciliate Cercozoa from soil and freshwater; usually do not swim, but glide on surfaces by means of the long posterior cilium to which the ventral surface of their typically soft bodies adheres (except *Cavernomonas*). Posterior centriole (C1) attached to side of younger anterior centriole (C2) at usually strongly obtuse angle (orthogonal only in clade A1a2) by fibrillar connections, the distal one weakly striated; both typically attached to anteriorly tapering nucleus. C2 points forwards, somewhat downwards and/or to left; C1 directed backwards, pointing downwards towards the substratum or to the left. Anterior cilium beats asymmetrically to the left; posterior typically does not undulate during smooth forward gliding. All but *Cavernomonas* have spindle-shaped body when gliding; cytoplasm adherent to posterior cilium drawn out into a posterior tail, often pointed; high propensity for making extensive non-locomotory feeding pseudopodia of seven types (depending on species): lamellipodia, filopodia (unbranching or branching), bulbous, finger-like, reticulopodia or axopodia (*Filomonas radiata* only). Most have contractile vacuoles and resting cysts; some have multinucleate and multiciliate syncytial or plasmodial stages in older cultures. Ciliar transition zone very short; with proximal hub-lattice structure; unlike glissomonads, cryothecomonads or *Katabia*, have a slender distal hub-spoke structure instead of a conspicuous dense distal transverse plate. Anterior centriole has two microtubular roots (vp2 without an associated dense plate, unlike glissomonads and thaumatomonads, and da of two microtubules), sometimes a third (dp2; *Eocercomonas* only); posterior centriole has nucleated at its basal half ventral root vp1 and sometimes (*Paracercomonas* only) also dorsal dp1 of two or three microtubules. A root of one or two microtubules (lr) nucleates near the junction of amorphous fibrillar material projecting from both centriole bases. Ventral posterior (vp1) and ventral anterior (but posterior-pointing) roots (vp2) typically mutually closely attached by dense material at least in their anterior region, where one crosses over the other. Microtubule nucleating centre (MNC) that nucleates a small cone of singlet microtubules associated with either or both centrioles: medial and ventral centrosome-like fibrillar root (fr) attached directly or indirectly to posterior centriole close to centriolar junction and base of dp1 if present, often connecting to nucleus; another fibrillar root (fs) usually present on dorsal side of C2; either or both of fr and fs may nucleate a small cone of microtubules. *Cercomonas*, *Eoercomonas*, *Filomonas*, *Neocercomonas*, *Cavernomonas*.

●●● Paracercomonadida Cavalier-Smith 2018

Cercomonads with a medial posterior microtubular root of two or three microtubules (dp1) attached to dorsal side of posterior centriole (unlike Cercomonadidae, whose only C1 root is vp1). Fibrillar MNC (fr) linked to and partially surrounding base of dp1, attached to nuclear-facing side of both centrioles, but mainly C1. Sheet-like MNC (fs) on dorsal side of C2 nucleates diverging single microtubules including two parallel conspicuous ones pointing backwards. Ventral roots vp1 and vp2 consistently to the right of plane passing longitudinally through posterior cilium (if viewed from its tip to base) and orthogonally to cell surface. Ciliar transition zone proximal hub-lattice with broad obvious hub; peripheral lattice not partially obscured by dense diaphragm-like material. Conspicuous dense ciliar axosome at base of central pair, sometimes with noticeable denser central hub structure; spokes radiating from it more obvious than nonagonal fibre. Centrioles in one plane, posterior centriole not offset. Left root, if present, points left; does not nucleate secondary microtubules. Pseudopodia most often finger-like or long thick, often branched filopodia: more rarely purely lamellipodial. Gliding cells typically smaller than Cercomonadida (3-18 µm). *Brevimastigomonas*, *Metabolomonas*, *Nucleocercomonas*, *Paracercomonas*, *Phytocercomonas*.

●●●● Glissomonadida Howe & Cavalier-Smith 2009 [Heteromitidae Kent 1880, emend. Mylnikov 1990, emend. Mylnikov & Karpov 2004; Bodomorphidae Hollande 1952]

Heterotrophic biciliates that are covered by a plasma membrane only but are not strongly amoeboid; ancestrally biciliates that glide upon substrata on the longer posterior cilium, but includes also one derived non-gliding genus (*Proleptomonas*); if exceptionally the anterior cilium is longer the posterior one is adherent to the cell and not used for gliding (*Proleptomonas* only); in gliding species the cell posterior is usually rounded and the cell most often oval or ovoid, not highly elongated; although some species may extend a protoplasmic tail temporarily, it is not drawn out along the posterior cilium as in most cercomonads; no cytopharynx or deep ciliar groove or pocket is evident and most species are singularly lacking in obvious morphological specializations; apart from *Proleptomonas*, which is exceptionally elongated and has a modified cytoskeleton, the nucleus is anterior and attached to the kinecid by well-developed fibrous roots; typically at least two posterior and one anterior microtubular centriolar roots; contractile vacuole usually in cell posterior; cilia of equal thickness, simple without parazonemal rod, hairs, or scales, sometimes acronematic; unlike in cercomonads, the ciliary transition region has a single dense transverse plate at its distal end; anterior cilium beats in ciliary fashion towards the left (as in cercomonads), and is sometimes reduced to a very short stub without an axoneme; only aerobic species currently known; mitochondria with tubular cristae; microbody attached to nuclear posterior except in *Proleptomonas*; almost exclusively inhabit soil or freshwater; Golgi dictyosomes typically associated with the nucleus, as is not the case in all Cercozoa; smooth walled cysts commonly present; sex unknown.

●●●●● Sandonidae Howe et al. 2009

Jerky gliders; anterior-pointing anterior cilium: *Sandona*, *Flectomonas*, *Neoheteromita*, *Mollimonas*.

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●● Dujardinidae Howe & Cavalier-Smith 2011
Jerky gliders; anterolateral pointing anterior cilium: *Dujardina*.

●●●● Bodomorphidae Hollande 1952, emend. Cavalier-Smith in Howe et al. 2009
Smoothly gliding biciliate cells with a shorter anterior cilium that points mainly sideways or posteriorly in parallel with the posterior one; in one genus with a prominent anterior rostrum; posterior centriolar base asymmetric, sharply angled with basally extended triplets on side facing nucleus. *Bodomorpha*.

●●●● Proleptomonadidae Howe et al. 2009
Swimmers. *Proleptomonas*.

●●●● Allapsidae Howe & Cavalier-Smith 2009
Smooth gliders; anterior cilium points sideways and somewhat backwards; centrioles symmetric. *Allapsa*, *Teretomonas*, *Allantion*.

●●● Viridiraptoridae Hess & Melkonian 2013
Biciliate naked cells, mostly occurring as rigid, variously shaped cells without rostrum or bulge. In ciliated state markedly exceeding 10 µm (contrasting most known glissomonad families). Capable of transforming into surface-attached amoeboid state, retaining cilia and showing bridge-like morphology with several distinct adhesion sites. Cell containing single ‘vesicular’ nucleus, close to ciliary apparatus, thus apical in ciliate state. Nucleolus spherical, roughly central, occasionally exhibiting lacuna/ae. Golgi bodies in close proximity to nuclear envelope. Cytoplasm colourless, often opaque due to diverse globules, granules and crystals. Digestive stages containing several globules of medium refractivity. Crystal-like structures restricted to starving cells, showing various shapes: 1) Small, isodiametric or slightly elongate, glistening particles, ~ 0.5–1 µm. 2) Slender, fusiform or needle-like rods, often 2–3 µm in length, rarely up to ~ 6 µm. Several mitochondria scattered throughout cell, slightly elongate to botuliform. Isodiametric extrusomes, ~ 0.5 µm as seen with light microscope, directly beneath plasma membrane, but not in pseudopodia. Several contractile vacuoles at non-defined positions in cell periphery, ≤ 2 µm in diameter (late diastole), non-synchronous. Cilia naked and heterodynamic, arising very close to each other in a slightly acute or right angle. Cells gliding on posterior cilium (mostly longer than anterior cilium), cell body not attaching to gliding cilium or to substrate. Flapping motion of anterior cilium often causing motions of cell body during gliding (rotation, jiggling, vibrating). Cells capable of fluttering swimming locomotion to different extent, involving both cilia. Heterotrophic nutrition, feeding by phagocytosis on dead or live eukaryotic cells, capable of local cell wall lysis to feed exclusively on protoplast material (e.g. in certain green algae), not bacterivorous. Propagation by binary fission, plasmodia not observed. Inhabiting freshwater-fed ecosystems. Phylogenetically defined as a well-supported, clade including the genera *Orciraptor* and *Viridiraptor*, but excluding the genera *Agitata*, *Allantion*, *Allapsa*, *Aurigamonas*, *Bodomorpha*, *Dujardina*, *Flectomonas*, *Mollimonas*, *Neoheteromita*, *Proleptomonas*, *Sandona* and *Teretomonas*. *Viridiraptor*, *Orciraptor*.

●●● Pansomonadidae Vickerman in Vickerman et al. 2005
Heterotrophic cell with two heterodynamic cilia, both cilia free from body; motile ciliate phase alternates with sedentary amoeboid phase; one amino acid insertion only between ubiquitin monomers. Clade includes last common ancestor of *Aurigamonas* and *Agitata*. *Agitata*, *Aurigamonas*.

●●● Sainouroidea<fnref n="36" /> Schuler et al. 2018 (R)
Ancestrally amoeboid biciliates, typically without scales or theca; cells often gliding on posterior cilium; tubular cristae or flat cristae; microbody attached to nucleus.

●●●● Sainouridae Cavalier-Smith 2008
Biciliate or tetraciliate phagotrophic, with one or two long, motile and highly acronematic posterior cilia possessing transition region hub-lattice and nonagonal fibre; posterior centrioles attached basally to a dense spiral fibre, and laterally to a microtubular root; one or two anterior stubby nipple-like cilia without these structures or roots, but with a ninefold submembrane skeleton; nucleus attached to cell surface and centrioles by striated rhizoplasts; centriole shorter (1—1.5X width) than in most Cercozoa (2—2.5 X width); fine tubular invaginations of inner membrane of nuclear envelope; peroxisome attached to the nuclear envelope; mitochondrial cristae flat or with peripheral vesicles, not elongated tubules as in most Cercozoa. *Acantho-Ius*, *Cholamonas*, *Homocognata*, *Sainouron*.

●●●● Helkesimastigidae Cavalier-Smith 2008
Biciliate semi-rigid cells with two parallel, longitudinally offset centrioles, one bearing a trailing cilium for gliding, the other bearing a ciliary stump or rarely a short motile laterally beating cilium; non-amoeboid phagotrophs with resting cysts; apical centrosomal plate with dorsal cape of single microtubules; dense forked fibre attaches the centriole bearing the long cilium

(continued)

<footnote n="36">³⁶A node including a probably monophyletic clade composed of Sainouridae and Thecofilosea is proposed, called Helkesida Cavalier-Smith 2018 (R).</footnote>
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

to the centrosomal plate and nucleates the single ventral microtubule; both centrioles attached to nucleus by striated rhizo-plasts. *Helkesimastix*.

●●●● Guttulinopsidae Olive 1970 (R)

*Guttulinopsis, Olivorum, Puppisaman, Rosculus*.

●●● Thecofilosea³⁶ Cavalier-Smith 2003, emend. Cavalier-Smith 2011

Ancestrally with robust organic extracellular theca, unlike most other Cercozoa, which are usually naked or with scales; ventral filose pseudopodia emerge from ventral groove; two cilia with diver gent kinetosomes, secondarily lost in Rhizaspidae and the euglyphid amoebae, and restricted to zoospores in Phaeodarea; ancestrally benthic gliding on posterior cilium only, but some secondarily planktonic swimmers among which Ebriacea have lost pseudopodia; theca with perforations for cilia and for pseudopodia, and three perforations in Phaeodarea (thus Tripylea Hertwig 1879), which have surrounded it by a pseudopodial net containing a pigmented phaeodium, thus converting it into a 'central capsule', but not homologous with that of Polycystinea of Radiolaria; silica scales absent, unlike many Imbricatea (see below), but hollow silica endoskeleton in all ebriids and most phaeodarians.

Incertae sedis Thecofilosea: *Mataza*.

●●●● Phaeodarea Haeckel 1879 [Tripylea Hertwig 1879]

Central capsule with thickened, double-layered, capsular wall containing two kinds of pores or openings; large opening known as an "astropylum" or oral pore with a protruding mass of cytoplasm, and smaller, typically lateral openings, as "parapylae", with thinner protruding strands of cytoplasm; dense mass of darkly pigmented granular cytoplasm, the "phaeodium," containing undigested debris, suspended in the extracapsulum; mineral skeletons, when present, composed of scattered spicules or hollow silica bars, joined by organic material; a wide variety of forms, including geodesic frameworks, spherical to polyhedral shells, or more solid, porous clam-shaped, bivalve shells; tubular mitochondrial cristae.

●●●●● Phaeoconchia Haeckel 1879

Central capsule enclosed within bivalve lattice shell composed of dorsal and ventral boat-shaped valves, which are completely separated and rarely connected by a ligament on the aboral pole. *Coelodendrum, Coelographis, Conchellium, Conchopsis*.

●●●●●● Phaeocystina Haeckel 1879

Central capsule suspended in the centre of the extra-capsular cytoplasmic network; skeleton absent or incomplete, composed of numerous solitary, scattered pieces or spicules without organic connections. *Aulacantha, Aulographis, Cannoraphis*.

●●●●●●● Phaeogromia Haeckel 1879

Central capsule located eccentrically, aborally, in simple lattice shell typically provided with large shell opening placed on the oral pole of the main axis; capsule opening surrounded by "teeth" or by peculiar elongate extensions known as "feet", sometimes with elaborate branches. *Castanella, Challengeron, Haeckeliana, Medusetta, Tuscarora*.

●●●●●●● Phaeosphaeria Haeckel 1879

Central capsule located in the centre of a simple or double spherical lattice shell, not bivalve, with a simple shell opening, lacking "feet" or "teeth". *Aulosphaera, Cannosphaera, Sagosphaera*.

●●●● Cryomonadida Cavalier-Smith 1993 (R)

rDNA trees show *Rhogostoma* (Rhizaspididae) within the cryomonads, so they evolved after the hypothesized ciliated common ancestor of Ebriacea and Cryomonadida by loss of cilia and are unrelated to *Pseudodifflugia*. Includes *Rhogostoma* (previously misidentified as *Lecythium*), *Cryothecomonas, Protaspis* (renamed *Protaspa* in Howe et al. 2011 as the name *Protaspis* was preoccupied).

●●●●●● Rhogostomidae Dumack et al. 2017

Thecate amoebae with ventral slit-like and not flexible cleft that emits filopodia; theca thin, flexible, in active cells adherent throughout to cell surface, consisting of single smooth dense layer outside and scarcely thicker than the plasma membrane; thus with bilateral symmetry; theca with exosomes (*Capsellina* or without (*Rhogostoma, Sacciforma*); phagotrophic (mainly bacteria, also yeasts, algae); division longitudinal, binary; sexual reproduction unknown. Electron microscopy of *Capsellina* and *Rhogostoma* by Simitzis and Le Goff (1981). *Rhogostoma, Sacciforma, Capsellina*.

●●●●●●● Protaspidae Cavalier-Smith 1993 (R)

Heterodynamic biciliated cells with cilia subapical separated by a protrusion; ciliary pit with funnel; dorsoventrally flattened and oval-shaped with parallel lateral sides; ventral longitudinal furrow in anterior half of cell; nucleus posterior with permanently condensed chromosomes; thickened cell wall with seven layers with pores for extrusome discharge; pseudopodia emerge from slits. *Cryothecomonas, Protaspa* (P)

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●● Ventricleftida Cavalier-Smith 2011</td><td>Strongly flattened oval cell with rigid theca without scales; two unequal cilia emerging subapically, often from apical notch—posterior cilium used for gliding on surfaces; ventral cleft from which branched filose pseudopods emerge for feeding separate from and posterior to ciliary groove unlike Thaumatomonadida and Auranticordis; with extrusomes. Ventrifissura, Verrucomonas.</td></tr><tr><td>●●●● Tectofilosida Cavalier-Smith 2003</td><td>Uninucleate cells (some may form fused multicellular aggregates) surrounded by an organic flexible tectum with one basal aperture for filopodia, sometimes including foreign mineral particles (agglutinated); cilia or silica scales absent; tubular mitochondrial cristae, cytotrophic. Pseudodifflugia, Rhizaspis, Fisculla.</td></tr><tr><td>●●●●● Chlamydophryidae de Saedeleer 1934 (R)</td><td>Chlamydophrys, Lecythium, Trachyrhizium, Diaphoropodon, Clypeolina, Leptochlamydophrys.</td></tr><tr><td>●●●● Ebriacea Lemmermann 1901 [Ebriidae Poche 1913; Ebriida Deflandre 1936]</td><td>Cells with two subapically inserting cilia; open internal skeleton of silica; phagotrophic without plastids. Ebria, Hermesinum, Botuliforma.</td></tr><tr><td>●●● Imbricatea Cavalier-Smith 2011 [Cavalier-Smith 2003]</td><td>Secreted surface silica scales or secondarily lost, except in basal lineages where ancestrally absent; tubular mitochondrial cristae; ciliary transition region longer than in cercomonads and sainouroids, and unlike them with dense distal plate but without the internal dense aggregates and elaborate extra structures opposite the thecal contact zone in cryomonads; groove and cilia secondarily lost by euglyphids; centrioles multiplied and reoriented to make four posteriorly directed gliding cilia in Auranticordis, which also lost pseudopodia; centrioles independently made parallel in the thaumatomonad/spongomonad subclade.<fnref n="37" /><br>Incertae sedis Imbricatea: Discomonas Chantangsi and Leader, 2010.</td></tr><tr><td>●●●● Spongomonadida Hibberd 1983 [Spongomonadidae Karpov 1990]</td><td>Biciliated cells with asymmetrical cell projection at anterior. Rhipidodendron, Spongomonas.</td></tr><tr><td>●●●●● Marimonadida Cavalier-Smith & Bass 2011</td><td>Without scales and without theca; marine heterotrophic biciliate swimming cells (Pseudopirsonia: diatom parasites) or interstitial gliding cells with somewhat deformable, semi-rigid pellicle underlain by muciferous bodies and four posterior cilia associated with ventral cleft (Auranticordis), or ciliated amoebae with two gliding posterior cilia and a non-ciliate feeding stage with broad lobose fan-like pseudopods (Rhabdamoeba). Differ from Euglyphida by the absence of silica scales and presence of cilia, and from thaumatomonads, the only other gliding imbricates, by absence of scales. Auranticordis, Pseudopirsonia, Rhabdamoeba, Abollifer, Cyranomonas</td></tr><tr><td>●●●● Variglissida Cavalier-Smith 2014 (R)</td><td>Clautriavia, Nudifila, Quadricilia.</td></tr><tr><td>●●●● Silicofilosea Adl et al. 2005, emend. Adl et al. 2012</td><td>Secreted surface silica scales or secondarily lost; tubular mitochondrial cristae.</td></tr><tr><td>●●●●●● Thaumatomonadida Shirkina 1987 [Thaumatomastigidae Patterson and Zoelfell 1991]</td><td>Heterotrophic, cells usually gliding that may swim also; body flattened and with two heterodynamic cilia inserting subapically and/or ventrally; some unikont; with extrusomes; filopodia produced subapically or from ventral groove; cysts; multinucleate and multiciliate stages known.</td></tr><tr><td>●●●●●●● Thaumatomonadidae Hollande 1952</td><td>Biciliated cells with ventral pseudopodia, long ventral posterior-pointing cilium used for gliding on surfaces unlike Peregriniidae (see below), and a much shorter anterior cilium, which is naked (Thaumatomonas, Allas) or with small scales (Reckertia, Thaumatomastix); siliceous scales formed in vesicles attached to mitochondria cover the rigid cell surface except for a ventral zone that emits pseudopodia for feeding; unlike Peregriniidae, do not transform completely into an amoeba; all have oval or triangular two-tiered body scales, with an upper plate bearing species-specific perforations supported at the oval ends or triangle corners by discrete struts, unlike Gyromitus; upper plate lacks central cleft with inrolled sides, unlike Peregrinia; Thaumatomastix only additionally has long spine scales with near-circular or rounded triangular bases. Allas, Hyaloselene, Reckertia, Thaumatomonas, Thaumatomastix, Ovaloplaca, Scutellomonas, Thaumatospina, Penardeugenia.</td></tr></tbody></table>

(continued)

<footnote n="37">³⁷Ancestral condition probably a gliding heterotrophic cell with two cilia with divergent kinetosomes, and relatively rigid pellicle that helped to define a distinct ventral groove from which filose pseudopods extended, but without the dense extracellular theca of The cofilosea or internal silica skeleton of Ebriacea and Phaeodaria. Includes Cercozoa with often imbricate silica scales and their closest nonscaly relatives.</footnote>
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●●● Esquamula Shiratori, Yabuki & Ishida 2012
Unicellular heterotrophic, with a short anterior cilium and a long posterior cilium; cells gliding with a posterior cilium; both cilia emerge from the same ciliar pit; cells with a rigid surface and without thecae or scales; filose or lobose pseudopodia sometimes emerging; slender extrusomes consist of shaft with a horizontal-stripe pattern and cap structure on the tip.

●●●●●●● Peregriniidae Cavalier-Smith 2011
With only oval two-tiered body scales and without scales on cilia or spine scales; scales either symmetric ovals with heavily out-turned upper and lower rims (as in *Gyromitus*) or asymmetric ovals with concave to flat lower surface and convex upper surface with rims more strongly laterally inrolled than at the ends (as in *Peregrinia*); in contrast to *Thaumatomonas*, ciliary pit apical not subapical and ventral, or cells so amoeboid as to lack defined shape; cilia not clearly differentiated into anterior and posterior; unlike *Thaumatomonadidae* no evidence for ciliary gliding; locomotion by swimming or slow amoeboid creeping. *Gyromitus*, *Peregrinia*.

●●●●● Euglyphida Copeland 1956, emend. Cavalier-Smith 1997
Testate amoebae, with a shell built of organic material; most taxa with secreted silica scales held together by organic cement; tubular mitochondrial cristae; filamentous pseudopodia; large and conspicuous nucleus easy to see in active cells using light microscopy, surrounded by vesicles. *Incertae sedis* Euglyphida: *Ampullataria*, *Euglyphidion*, *Heteroglypha*, *Matsakision*, *Pareuglypha*, *Pileolus*.

●●●●●●● Euglyphina Kosakyan et al. 2016
Test covered with elliptical, discoid or denticulated siliceous plates. The least inclusive clade containing *Assulina*, *Euglypha*, *Sphenoderia* and *Trinema*.

●●●●●●●● Assulinidae Lara et al. 2007
Test with a terminal aperture composed of elliptic plates disposed in a regular, alternate pattern: test strongly compressed; no specialized type of scales around the aperture; shape flattened in cross-section; in litter and mosses. *Assulina*, *Placocista*, *Valkanovia*.

●●●●●●● Sphenoderiidae Chatelain et al. 2013
Circular to elliptical silica scales that can be of different sizes and shapes, but without indentations; aperture surrounded with small round or oval scales; slightly subterminal aperture; shape flattened or circular in cross-section in litter and mosses, and freshwater plants; *Sphenoderia*, *Trachelocorythion*, *Deharvengia*.

●●●●●●●● Trinematidae Hoogenraad & De Groot 1940, emend Adl et al. 2012
Test with bilateral symmetry; scales oval or round, sometimes of both types; specialized tooth-shaped scales around the aperture, which is located on the side of the shell; aperture invaginated in some taxa; shape flattened in cross-section; in litter and mosses; *Corythion*, *Playfairina*., *Puytoracia*., *Trinema*.

●●●●●●● Euglyphidae Wallich 1864, emend Lara et al. 2007
Test with a terminal aperture; thin elliptical scales; presence of specialized scales around the aperture with typical indentation; shape flattened or circular in cross-section; in litter and mosses, freshwater sediments and plants. *Euglypha*, *Scutiglypha*.

●●●●●●● Tracheleuglypha Deflandre 1928
Test reinforced with relatively large, discoid plates; cross-section circular; without specialized scales around the aperture. (There is a single sequence from this genus, which typically causes long branches in SSU rRNA gene phylogenies (Lara et al., 2007) and the node is unresolved).

●●●●●● Cyphoderiidae de Saedeleer 1934
Scales circular, oval or kidney-shaped, juxtaposed or imbricated; test aperture angled, some with collar; shape circular in cross-section; in freshwater sediments and plants, supralittoral sands. *Campuscus*, *Corythionella*, *Cyphoderia*, *Messemvriella*., *Pseudocorythion*, *Schaudinnula*.

●●●●●●● Paulinellidae de Saedeller 1934, emend. Adl et al. 2012
Test with self-secreted siliceous reinforcements, or proteinaceous; when present, scales are elongated, with length perpendicular to aperture. At least two genera (*Micropyxidiella* and *Ovulinata*) with totally organic test without silica scales; in litter and mosses, freshwater plants, marine sediments and plankton. *Micropyxidiella*, *Ovulinata*, *Paulinella*.

●●● Metromonadea Cavalier-Smith 2007, emend. Cavalier-Smith 2011
Nonpseudopodial marine gliding biciliated cells; cytotrophic predator; nonthecate but with a dense single or double-layered surface coat that may extend up cilium; extrusomes highly elongated. *Metromonas*, *Metopion*, *Micrometopion*, *Kiitoksia*.

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●● Granofilosea Cavalier-Smith & Bass 2009</td><td>With very fine branching or unbranched granuloreticulopodia bearing obvious extrusomes as the granules at frequent rather regular intervals, or with radiating, sometimes branched, axopodia with similar granules; pseudopodia supported by internal microtubules and typically appressed to the sub stratum during feeding, in a semi-immobile state; in most species, pseudopodia do not anastomose; some with biciliated swimming or gliding stage.</td></tr><tr><td>●●●● Incertae sedis Granofilosea*: Apogromia, Kibisidytes, Leucodictyon, Limnofila, Mesofila, Microcometes, Microgromia, Nanofila, Reticulamoeba and probably Belaria, Ditrema, Heliomorpha (=Dimorpha) and Paralieberkuehnia.</td><td></td></tr><tr><td>●●●●● Massisteridae Cavalier-Smith 1993 (R)</td><td>Massisteria, Minimassisteria.</td></tr><tr><td>●●●●● Clathrulinidae Claus 1874 [Desmothoracida Hertwig and Lesser 1874]</td><td>Extracellular capsule or lorica attached to substrate, or cell free-floating; sometimes mucous sheath around cell; pseudopodia branching capable of anastomosis, and with microtubules, but not organized in any recognizable pattern; kinetocyst extrusomes on pseudopodia; tubular mitochondrial cristae; biciliated and amoeboid stages; can be colonial; cysts. Actinosphaeridium, Cienkowskya*, Clathrulina, Hedriocystis, Penardiophrys. Incertae sedis Clathrulinidae: Servetia.</td></tr><tr><td>●●● Chlorarachnea Hibberd & Norris 1984</td><td>Amoeboid with plastids of secondary origin; plastid containing chlorophylls a and b, associated with a nucleomorph and surrounded by four membranes in total; usually reticulate pseudopodia with extrusomes; cell bodies often anastomosing; with a biciliated dispersal stage. Also includes minute marine picoplanktonic bacterivorous cell with single long acronematic smooth cilium (Minorisa Del Campo, 2013). Amorphochlora, Bigelowiella, Chlorarachnion, Cryptochlora; Gymnochlora, Lotharella, Minorisa, Partenskyella, Viridiuvalis.</td></tr><tr><td>●● Endomyxa Cavalier-Smith 2002, emend. Bass & Berney in Adl et al. 2019 (R)</td><td>This clade has varied somewhat in definition and composition but retains a core group of Rhizaria robustly distinct from Cercozoa and Retaria. Retaria as defined here is either a sister clade to Endomyxa, or branches within it. Numerous environmental lineages exist without morphological data. It is defined here as the least inclusive clade containing the last common ancestor of Vampyrrellida, Phyto myxea, Filoreta, Gromia, Ascetosporea, and all its descendants.</td></tr><tr><td>●●● Vampyrrellida West 1901, emend. Hess et al. 2012</td><td>Exclusively heterotrophic, naked, phagotrophic amoeboid organisms; life cycle includes amoeboid, free-moving trophozoites alternating with an obligatory digestive cyst, in which cell division usually take place; several taxa can fuse to form plasmodia and reach considerable sizes; sexual processes unknown; cytoplasm often differentiated into a finely granular, sometimes highly vacuolated part and structure-less hyaloplasm, the latter often surrounding the main cell body, but at least constituting the pseudopodia; free-living in freshwater, soil, or marine environments. Arachnula, Gobiella, Hyalodiscus, Lateromyxa, Leptophrys, Platyreta, Thalassomyxa, Theratromyxa, Vampyrella, Vernalophrys, Penardia.</td></tr><tr><td>●●●● Phytomyxea Engler & Prantl 1897</td><td>Amoeboid or plasmodial feeding cells producing biciliate or tetraciliate cells; some with specialized solid extrusome—"satchel"— for penetrating host cells; with distinctive cruciform mitotic profile due to elongate persistent nucleolus lying orthogonal to metaphase plate; parasites or parasitoids of plants or stramenopiles.</td></tr><tr><td>●●●●● Plasmodiophorida Cook 1928</td><td>Plasmodiophora, Polymyxa, Woronina, Ligniera, Sorosphaerula, Spongospora.</td></tr><tr><td>●●●●● Phagomyxida Cavalier-Smith 1993 (R)</td><td>Phagomyxa, Maullinia.</td></tr><tr><td>●●● Filoreta Bass & Cavalier-Smith 2009</td><td>Aciliate, naked, free-living, mainly bacterivorous reticulose amoebae that form extensive multinucleate open-mesh nets. Filoreta.</td></tr><tr><td>●●●● Gromia Dujardin 1835</td><td>Test of organic material, brown and opaque, with single aperture; filopodia branched, with non-granular cytoplasm; filopodia anastomose but not into a reticulum; multinucleate; tubular mitochondrial cristae; ciliated dispersal cells or gametes. Gromia.</td></tr><tr><td>●●●● Ascetosporea Sprague 1979, emend. Cavalier-Smith 2009</td><td>Complex spore structure—one or more cells, with one or more sporoplasms, without polar capsules or filaments; parasites of invertebrates.</td></tr><tr><td>●●●●● Haplosporida Caullery & Mesnil 1899</td><td>Distinctive lidded spores; during spore development, spore wall produced inside of outer membrane of invaginated area; without polar capsules or polar filaments; spore anterior opening covered by hinged operculum; intranuclear spindle, a</td></tr></tbody></table>

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

rudiment of which persists in interphase nuclei ("kernstab"); tubular mitochondrial cristae; plasmodial endoparasites of marine and sometimes freshwater animals. *Bonamia*, *Haplosporidium*, *Minchinia*, *Urosporidium*.

●●●● Mikrocytida Hartikainen et al. 2013

Microcell parasites within the genera *Mikrocytos* Farley et al., 1988 and *Paramikrocytos* Hartikainen et al. 2013 infecting aquatic invertebrates. Plasmodial (*Paramikrocytos*) and unicellular (*Mikrocytos* and *Paramikrocytos*) stages. Phylogenetically highly distinct, and defined as all lineages branching in a clade including *Mikrocytos mackini* and *Paramikrocytos canceri*. Spores unknown, in contrast to most haplosporids. *Mikrocytos*, *Paramikrocytos*.

●●●● Paramyxida Chatton 1911

Spore bicellular consisting of a parietal cell and one sporoplasm; without orifice. *Marteilia*, *Paramyxa*, *Paramarteilia*, *Marteilioides*, *Eomarteilia*.

●●●● Claustrosporidium Larsson 1987

Uninucleate sporoplasm with haplosporosomes; spore wall with no orifice and formed on sporoplasm surface, not intracellular; spores without operculum and lingula.

●●●● Paradiniida Schiller 1935

Unlike other ascestosporans, have a biciliated dispersal phase with two unequal cilia; marine parasites of Crustacea with multinucleate plasmodial trophic phase. *Paradinium*, "spot prawn parasite".

●● Retaria Cavalier-Smith 2002 (R)

Mainly marine heterotrophs, with reticulopodia or axopodia, and usually having various types of skeleton.

●●● Foraminifera d'Orbigny 1826

Filopodia with granular cytoplasm, forming branching and anastomosing network (reticulopodia); bidirectional rapid (10 mm/s) transport of intracellular granules and plasma membrane domains; tubular mitochondrial cristae; fuzzy-coated organelle of unknown function in reticulopodia; polymorphic assemblies of tubulin as (i) conventional microtubules singly or in loosely organized bundles, (ii) single helical filaments and (iii) helical filaments packed into paracrystalline arrays; majority of forms possess a test, which can be organic walled, agglutinated or calcareous; unusual characteristic beta-tubulin; wall structure in naked and single-chambered forms quite variable for "naked" athalamids, such as *Reticulomyxa*, thicker veins vested with an amorphous, mucoid material; for thecate (soft-walled) species, such as members of the genus *Allogromia*, proteinaceous with little or no foreign material; for agglutinated species, foreign materials bound with an amorphous or fibrous organic matrix; for multichambered (polythalamous) forms, walls containing agglutinated material or mineralized with calcite, aragonite, or silica; life cycle often comprising an alternation of asexually reproducing agamont and sexually reproducing gamont.

*Incertae sedis* Foraminifera: *Lagenida* Delage and Hérouard 1896

*Incertae sedis* Foraminifera: *Heterogromia*, *Komokiacea*.

●●●●● Monothalamea Pawlowski et al. 2013

Single chamber (monothalamous) test with an organic or agglutinated wall; the group comprises all genera traditionally included into the *Allogromiida*, *Astrorhizida*, and the *Xenophyophorea*; although considered marine there are 4-5 clades of fresh water species, the diversity of this mainly unfossilized group is poorly known and has been largely overlooked in micropaleontologically oriented foraminiferal research. *Allogromia*, *Astrammina*, *Crithionina*, *Notodendrodes*, *Psammophaga*, *Bathysiphon Reticulomyxa*.

●●●●● Tubothalamea Pawlowski et al. 2012

Bi- or multichambered test with tubular chambers at least in the juvenile stage; wall agglutinated or calcareous; in ancestral forms the test is composed of a spherical proloculus followed by a planispirally enrolled tubular chamber in *Ammodiscus*, *Spirillina* and *Cornuspira*; more derived forms have multichambered tests; the highly diverse group of extinct large *Fusulinida* probably also belong to this clade.

●●●●●● Miliolida Delage & Hérouard 1896

Test bi- or multichambered, wall agglutinated or calcareous of high-magnesium calcite with randomly oriented crystals refracting light in all directions and resulting in a porcelaneous appearance of the test; generally imperforate walls; chambers tubular or elongate, often planispirally coiled; some with complex internal structures adapted to host algal endosymbionts. *Alveolina*, *Cornuspira*, *Miliammina*, *Pyrgo*, *Quinqueloculina*, *Sorites*.

●●●●●● Spirillinida Hohenegger & Piller 1975

Test composed of proloculus followed by an enrolled tubular chamber, undivided or with few chambers per whorl; wall of low-magnesium calcite, optically a single crystal. *Patellina*, *Spirillina*.

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><tr><td>●●●●● Ammodiscidae Reuss 1862</td><td>Test composed of globular proloculus followed by a coiled undivided tubular chamber with terminal aperture; wall agglutinated. Ammodiscus, Glomospira.</td></tr><tr><td>●●●●● Globothalamea Pawlowski et al. 2012</td><td>Test multichambered, typically trochospirally enrolled but may be triserial, biserial or uniserial; chambers globular or crescent-shaped in early stage; wall agglutinated or calcareous.</td></tr><tr><td>●●●●●● Rotaliida Delage & Hérouard 1896</td><td>Wall of low-magnesium calcite, optically radial, bilamellar, perforate; some with internal canal system. Subdivisions proposed below.</td></tr><tr><td>●●●●●●● Planorbulinidae Schwager 1877 (Planorbulinella, Hyalinea)</td><td></td></tr><tr><td>●●●●●●● Discorboidea Ehrenberg 1838</td><td></td></tr><tr><td>●●●●●●●● Discorbidae Ehrenberg 1838 (Discorbis)</td><td></td></tr><tr><td>●●●●●●●● Rosalinidae Reiss 1963 (Rupertina, Discanomalina, "Rosalina", Gavelinopsis, Planorbulina)</td><td></td></tr><tr><td>●●●●●●●● Rotalioidea Ehrenberg 1839, emend. Pawlowski 2013</td><td></td></tr><tr><td>●●●●●●●● Elphidiidae Galloway 1933 (Elphidium)</td><td></td></tr><tr><td>●●●●●●●● Ammoniidae Saidova, 1981 (Ammonia)</td><td></td></tr><tr><td>●●●●●●●● Elphidiellidae Holzmann & Pawlowski 2017 (Elphidiella)</td><td></td></tr><tr><td>●●●●●●●● Haynesinidae Mikhalevich 2013 (Haynesina, Aubignyna)</td><td></td></tr><tr><td>●●●●●●●● Incertae sedis Cribroelphidium, "Elphidium", Proteiphidium</td><td></td></tr><tr><td>●●●●●●●● Glabratelloidea (Loeblich & Tappan 1964)</td><td></td></tr><tr><td>●●●●●●●● Rotaliellidae Loeblich & Tappan 1964 (Rotaliella, Rossyatella)</td><td></td></tr><tr><td>●●●●●●●● Buliminoididae Seiglie 1970 (Buliminoides)</td><td></td></tr><tr><td>●●●●●●●● Glabratellidae Loeblich & Tappan 1964 (Glabratella, Glabratellina, Angulodiscorbis, Planoglabratella)</td><td></td></tr><tr><td>●●●●●●●● Calcarinoidea (Schwager 1876)</td><td></td></tr><tr><td>●●●●●●●● Calcarinidae Schwager 1876 (Neorotalia, Baculogypsina, Baculogypsinooides, Schlumbergerella, Pararotalia)</td><td></td></tr><tr><td>●●●●●●●● Nummulitoidea de Blainville 1827</td><td></td></tr><tr><td>●●●●●●●● Nummulitidae de Blainville 1827 (Nummulites, Operculinella, Cycloclypeus, Heterostegina, Operculina, Planoperculina, Planostegina)</td><td></td></tr><tr><td>●●●●●●●● Serioidea (Holzmann & Pawlowski 2017)</td><td></td></tr><tr><td>●●●●●●●● Uvigerinidae Haeckel 1894 (Uvigerina, Rectuvigerina, Trifarina)</td><td></td></tr><tr><td>●●●●●●●● Bolivinitidae Glaessner 1937 (Bolivina, Brizalina, Saidovina)</td><td></td></tr><tr><td>●●●●●●●● Cassidulinidae d'Orbigny 1839 (Globocassidulina, Cassidulinoides, Evolvocassidulina, Islandiella, Ehrenbergina)</td><td></td></tr><tr><td>●●●●●●●● Sphaeroidinidae Cushman 1927 (Sphaeroidina)</td><td></td></tr><tr><td>●●●●●●●● Globobuliminidae Cushman 1927 (Globobulimina)</td><td></td></tr><tr><td>●●●●●●●●● Incertae sedis Rotaliida:</td><td></td></tr><tr><td>●●●●●●●● Nonionidae Schultze 1854 (Nonion, Nonionella, Nonionellina, Nonionoides)</td><td></td></tr><tr><td>●●●●●●●● Virgulinellidae Loeblich & Tappan 1984 (Virgulinella)</td><td></td></tr><tr><td>●●●●●●●● Buliminidae Jones 1875 (Bulimina)</td><td></td></tr><tr><td>●●●●●●●● Epistominellidae Holzmann & Pawlowski 2017 (Epistominella)</td><td></td></tr><tr><td>●●●●●●●● Stainforthiidae Reiss 1963 (Stainforthia, Gallitellia)</td><td></td></tr><tr><td>●●●●●●●● Cibicididae Cushman 1927 (Cibicides, Cibicidoides, Heterolepa)</td><td></td></tr><tr><td>●●●●●●●● Chilostomellidae Brady 1881 (Chilostomella)</td><td></td></tr><tr><td>●●●●●●●● Pullenidae Schwager 1877 (Pullenia)</td><td></td></tr><tr><td>●●●●●●●● Nuttalidae Saidova 1981 (Nuttalides)</td><td></td></tr><tr><td>●●●●●●●● Discorbinellidae Sigal 1952 (Discorbinella, Hanzawaia)</td><td></td></tr><tr><td>●●●●●●●● Astronionidae Cushman & Edwards 1937 (Astrononion)</td><td></td></tr><tr><td>●●●●●●●● Oridorsalidae Loeblich & Tappan 1984 (Oridorsalis)</td><td></td></tr><tr><td>●●●●●●●● Melonidae Holzmann & Pawlowski 2017 (Melonis)</td><td></td></tr><tr><td>●●●●●●●● Cymbaloporidae Cushman 1927 (Cymbaloporella)</td><td></td></tr><tr><td>●●●●●●●● Rubratelliidae Holzmann & Pawlowski 2017 (Rubratella)</td><td></td></tr><tr><td>●●●●●●●● Murrayinelliidae Holzmann & Pawlowski 2017 (Murrayinella)</td><td></td></tr></table>

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●●● Globigerinida Delage & Hérouard 1896 (P)</td><td>Wall of low-magnesium calcite, bilamellar, perforate; surface may be covered with fine, elongate spines; planktonic mode of life. <i>Globigerina, Globigerinoides, Globorotalia, Orbulina</i>.</td></tr><tr><td>●●●●● Robertinida Loeblich & Tappan 1984</td><td>Wall of hyaline, perforate, optical radial aragonite; chambers with internal partition. <i>Hoeglundina, Robertina, Robertinoides</i>.</td></tr><tr><td>●●●●● Textulariida Delage & Hérouard 1896 (P)</td><td>Wall agglutinated, with foreign particles attached to organic lining or cemented by low-magnesium calcite. <i>Cyclammina, Eggerella, Reophax, Textularia, Trochammina</i>.</td></tr><tr><td>●●●●● Carterina Brady 1884 [Carterinida Loeblich & Tappan 1981]</td><td>Wall composed of rod-like spicules of low-magnesium calcite held in organic lining; chambers numerous, trochospirally coiled. <i>Carterina</i>.</td></tr><tr><td>●●● Radiolaria Müller 1858, sensu Adl et al. 2005</td><td>Cells with distinctive organic, nonliving, porous capsular wall surrounding the intra-capsulum, which contains the nucleus or nuclei and cytoplasmic organelles; tubularcristae; axopodia supported by internal microtubules, extending distally through the capsular wall pores and connecting to a frothy external layer, the extracapsulum; extracapsulum containing digestive vacuoles and in some cases algal and/or cyanobacterial symbionts; skeletons, when present, of amorphous silica (opal) or strontiumsulphate (in Acantharia) and varying in shape from simple scattered spicules to highly ornate geometric-shaped shells, within and/or surrounding the central capsule; the siliceous skeleton is secreted within a specialized cytoplasmic envelope (cytokalymma) that dynamically determines the shape of the skeletal matter.</td></tr><tr><td>●●●● Acantharea Haeckel 1881, emend. Mikrjukov 2000</td><td>Cell surrounded by fibrillar capsule outside of cell membrane; axopodia, spicules and amoeboid anastomosing dynamic network of irregular pseudopodia extending from the capsule; this outer network (ectoplasm) surrounded by fibrillar periplasmic cortex; inner cell region inside capsule (endoplasm) holding the organelles; axopodia, supported by microtubular arrays, with kinetocyst extrusomes and with a centroplast-type centrosome at base of each spicule; 20 radial spicules of strontium sulphate merged at cell centre; spicule tips attached to contractile myonemes at periplasm; tubular mitochondrial cristae; often with algal symbionts in endoplasm, and captured prey in ectoplasm network; asexual reproduction unknown; sexual reproduction involving consecutive mitotic and meiotic divisions that ultimately release biciated isogametic cells; only marine isolates known.</td></tr><tr><td>●●●●● Chaunocanthida Schewiakoff 1926</td><td>Pigmented endoplasm, clears towards periphery; many small nuclei in endoplasm; clear ectoplasm with periplasmic cortex; sexual reproduction in gamontocyst; small plaques as lithosomes synthesized in Golgi and forming the gamontocyst wall; litholophus stage prior to reproduction; hexagonal microtubular arrays in axopodia; contractile matrix at base of spicules. <i>Amphiacon, Conacon, Gigartacon, Heteracon, Stauracon</i>.</td></tr><tr><td>●●●●● Holocanthida Schewiakoff 1926</td><td>Pigmented endoplasm, clears towards periphery; many small nuclei in endoplasm; sexual reproduction in gamontocyst; with lithosomes forming the gamontocyst wall; dodecagonal microtubular arrays in axopodia. <i>Acanthochiasma, Acanthocolla, Acanthoplegma</i>.</td></tr><tr><td>●●●●● Symphyacanthida Schewiakoff 1926</td><td>Pigmented endoplasm, clears towards periphery; ectoplasm clear; single large central nucleus; outer endoplasm with anastomosing pseudopodia; capsule and periplasmic cortex visible with light microscopy; sexual reproduction in gamontocyst with lithosomes forming the gamontocyst wall. <i>Amphilithium, Astrolonche, Pseudolithium</i>.</td></tr><tr><td>●●●●● Arthracanthida Schewiakoff 1926</td><td>Thick capsule clearly demarcates pigmented endoplasm from ectoplasm; axopodia with hexagonal microtubular arrays; many nuclei in endoplasm; algal symbionts in all known species, except at reproduction; sexual reproduction without gamontocyst. <i>Acanthometra, Daurataspis, Dictyacantha, Diploconus, Phractopelta, Phyllostaurus, Pleuraspis, Stauracantha</i>.</td></tr><tr><td>●●●●● Taxopodida Fol 1883</td><td>Axopodial pseudopods without kinetocysts (extrusomes), used for motility as oars; axopodial microtubules originate from depressions in nuclear envelope; microtubules in axoneme arranged in irregular hexagons; siliceous tangential spicules, with external radial spicules. <i>Sticholonche</i>, several environmental clades.</td></tr></tbody></table>

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>
  <tbody>
    <tr>
      <td>●●●● Polycystinea Ehrenberg 1838, emend. Haeckel 1887</td>
      <td>Central capsule spherical to ovate with round pores in the capsular wall either distributed uniformly on the surface of a spherical capsular wall or localized at one pole of an ovate capsular wall; skeleton either absent or when present, composed of spicules or forming elaborate geometric-shaped, porous or latticed shells.</td>
    </tr>
    <tr>
      <td>●●●●● Spumellaria Ehrenberg 1875, Haeckel 1887, emend. Riedel 1967</td>
      <td>Central capsule typically spherical with uniformly distributed round pores in the capsular wall; skeleton either absent or when present, composed of spicules or forming latticed shells (spicules single, or multiple and concentrically arranged). Subdivisions not fully resolved. Actinomma, Didymocyrtis, Euchitonia, Hexacontium, Hexalonche, Hexastylus, Octodendron, Plegmosphaera, Saturnalis, Spongaster, Spongosphaera.</td>
    </tr>
    <tr>
      <td>●●●●●● Nassellaria Ehrenberg 1875, emend. Haeckel 1887</td>
      <td>Central capsule ovate with pores localized at one pole; skeleton, when present, composed of a simple tripod, a sagittal ring without tripod or porous helmet-shaped "cephalis" enclosing the central capsule. Artostrobus, Eucyrtidium, Lithomelissa, Pterocanium, Pterocorys.</td>
    </tr>
    <tr>
      <td>●●●●●●● Collodaria Haeckel 1887</td>
      <td>Skeleton either absent or when present, composed of scattered spicules within the extracapsulum; solitary or colonial forms. Acrosphaera, Collosphaera, Collozoum, Sphaerozoum, Rhaphidozoum, Siphonsphaera, Thalassicolla.</td>
    </tr>
    <tr>
      <td>●● Aquavolonida Bass & Berney 2018</td>
      <td>Defined as the least inclusive clade containing the last common ancestor of the rhizarian lineages sharing a unique combination of 18S rRNA sequence signatures consisting of two complementary substitutions from U-A to G-C and from G-C to C(U)-G(A) in helix 11, one complementary substitution from A-T to C(T)-G(A) in helix 48, and a specific motif of two adjacent substitutions (AU instead of YG) in a nonbinding part of the 3° stem of helix 25 and all their descendants.</td>
    </tr>
    <tr>
      <td>●●● Aquavolon Tikhonenkov, Mylnikov, & Bass 2018</td>
      <td>With two smooth subapical heterodynamic cilia; kinetosomes approximately at right angle to each other and connected by at least one fibril; posterior kinetosome is very long (&gt; 1 µm); shape slightly flexible, not flattened, with remarkable lateral depression in the middle lateral point of the cell body; single contractile vacuole and nucleus located anteriorly; several mitochondria with tubular cristae; rapidly swimming and rarely gliding protist; cytotrophic.</td>
    </tr>
    <tr>
      <td>●● Tremula Howe et al. 2011 [=Tremulida Howe et al. 2011] M</td>
      <td>Heterotrophic and phagotrophic biciliates with long anterior and posterior cilia; glide on surfaces by means of both cilia, one pointing forwards and one backwards; without light microscopically visible theca, scales or cytostome. Molecular phylogenies show it is a sister clade to Aquavolonida. Tremula longifila.</td>
    </tr>
    <tr>
      <td>● Haptista Cavalier-Smith 2003</td>
      <td>Thin microtubule-based appendages (haptonema or axopodia) used for feeding; complex mineralized (siliceous or calcareous) scales.</td>
    </tr>
    <tr>
      <td>●● Haptophyta Hibberd 1976, ex. Edvardsen & Eikrem 2000</td>
      <td>Autotrophic, mixotrophic or heterotrophic single cells; some in colonies, or a few filamentous; motile cells mostly possessing a haptonema, a filiform appendage situated between one pair of cilia; characteristic cell covering of unmineralized and/or mineralized scales; motile cells with two cilia generally without appendages, inserted apically or subapically; usually one or two chloroplasts with thylakoids in groups of three and with no girdle lamella; chloroplasts with immersed or bulging pyrenoid; nucleus usually posterior or central; outer membrane of nuclear envelope continuous with outer chloroplast membrane; major pigments chlorophylls a, c1, and c2 with c3 in prymnesiophyceans, fucoxanthin (e.g. 19' hexanoyloxyfucoxanthin, 19'butanoyloxyfucoxanthin), beta-carotene, diadinoxanthin and diatoxanthin; chrysolaminarin often the main storage product; eyespots recorded in a few genera (Pavlova, Diacronema); haplo-diploid life cycles including heteromorphic alternating stages; motile, ciliated stage may alternate with nonmotile palmelloid (colonial), single-celled or filamentous stages, or with motile, ciliated stages; sexual reproduction may be common in prymnesiophyceans; some species ichthyotoxic.</td>
    </tr>
    <tr>
      <td>●●● Pavlovales Green 1976</td>
      <td>Biciated with unequal cilia inserted subapically or laterally; body scales absent; shorter cilium may have a swelling with densely staining projections on the side adjacent to the cell, the longer cilium may have thin hairs or scales; haptonema short, tapered and noncoiling; single chloroplast, sometimes with an eyespot beneath the short cilium. Diacronema, Exanthemachrysis, Pavlova, Rebecca.</td>
    </tr>
  </tbody>
</table>

(continued)

<footnote n="38"><sup>38</sup>Centrohelida Kühn was introduced to include both centrohelids and gymnosphaerids; Febvre-Chavalier and Febvre (1984) were the first who recognized and named this taxon.</footnote>
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●● Prymnesiophyceae Hibberd 1976</td><td>Unicellular or colonial, mostly ciliated cells with mineralized and/or unmineralized scales covering the cells; some species exhibit two stages in the life cycle, with a diploid nonmotile or motile stage alternating with a ciliated haploid stage; haptonema may be long and coiling to short and noncoiling; cilia of equal or subequal lengths inserted apically or subapically.</td></tr><tr><td>●●●● Prymnesiales Papenfuss 1955, emend. Edvardsen & Eikrem 2000</td><td>Motile or nonmotile cells, usually with two cilia and a coiling or flexible haptonema; covering of organic, sometimes spiny scales, sometimes absent; some alternate life cycle stages reported. <i>Chrysochromulina</i>, <i>Chrysocampanula</i>, <i>Dicrateria</i>, <i>Haptolina</i>, <i>Prymnesium</i>, <i>Pseudohaptolina</i>.</td></tr><tr><td>●●●●● Phaeocystales Medlin 2000</td><td>Motile cells with two cilia and short noncoiling haptonema; one to four chloroplasts per cell; the cell covered with scales of two sizes; life cycle may consist of nonmotile and motile stages; nonmotile cells colonial and embedded in gelatinous material. <i>Phaeocystis</i>.</td></tr><tr><td>●●●●● Isochrysidales Pascher 1910, emend. Edvardsen & Eikrem 2000</td><td>Motile or nonmotile cells; haptonema rudimentary or absent; motile cells covered with small organic scales; nonmotile cells usually covered with coccoliths. <i>Emiliania</i>, <i>Gephyrocapsa</i>, <i>Isochrysis</i>, <i>Ruttnera</i>, <i>Tisochrysis</i>.</td></tr><tr><td>●●●●●● Coccolithales Schwarz 1932, emend. Edvardsen & Eikrem 2000</td><td>Cells with calcified organic scales during some stage of the life cycle; single or alternating stages in the life cycle; haptonema short or highly reduced; some species lack chloroplasts. <i>Balaniger</i>, <i>Calciosolenia</i>, <i>Coccolithus</i>, <i>Hymenomonas</i>, <i>Chrysotila</i>, <i>Wigwamma</i>.</td></tr><tr><td>●● Centroplasthelida Febvre-Chevalier & Febvre 1984<sup>38</sup> [Centrohelea Kühn 1926 sensu Cavalier-Smith in Yabuki et al. 2012; Centro-heliozoa Dürrschmidt & Patterson 1987]</td><td>Without cilium; naked or covered with mucous, usually with organic or mineralized elements (scales) embedded in it; axopodia supported by microtubules forming hexagon-related pattern; ball-and-cone structure containing kinetocyst extrusomes along axopodia; centrosome as trilaminar disc with fibrous electron-dense cortex, flat mitochondrial cristae.</td></tr><tr><td><i>Incertae sedis</i> Centroplasthelida: Spiculophryidae Shishkin & Zlatogursky 2018 (M)</td><td>Centrohelids typically lacking silica scales but with numerous thin, pointed organic spicules tapering towards acute apices; expansions (but sometimes noticeably short) in panacanthocystid increase regions (PINs) 2, 6, 7, 10, 12 of SSU rRNA gene present. <i>Spiculophrys</i>.</td></tr><tr><td><i>Incertae sedis</i> Centroplasthelida: <i>Parasphaerastrum</i>.<sup>39</sup></td><td></td></tr><tr><td>●●● Pterocystida Cavalier-Smith and von der Heyden 2007, emend. Shishkin and Zlatogursky 2018 (R)</td><td>The least inclusive clade, containing <i>Pterocystis devonica</i>, <i>Raphidiophrys heterophryoidea</i> and <i>Choanocystis curvata</i> but not <i>Acanthocystis nichollsi</i>.</td></tr><tr><td>●●●● Raphidista Shishkin & Zlatogursky 2018</td><td>Typically with unconsolidated layer of flattened siliceous plate scales, which consist of upper and lower plates, connected by internal septae or with two types of scales: plate scales of inner layer are flattened, simple in structure, usually ornamented with axial rib, outer spine scales with cylindrical shaft attached on the heart-shaped base plate, which provides bilateral symmetry.</td></tr><tr><td>●●●●● Choanocystidae Cavalier-Smith & von der Heyden 2007 (M)</td><td>Two contrasting types of siliceous scales, oval or bilobed tangential plate scales (margin not hollow and inrolled) forming the inner layer and outer bipartite spine scales consisting of a vertical stalk, sometimes curved or branched but lacking lateral wings, emanating from near a strong indentation on one side of a flat horizontal base. <i>Choanocystis</i>.</td></tr><tr><td>●●●●●● Raphidiophryidae Febvre-Chevalier & Febvre 1984, emend. Shishkin & Zlatogursky 2018 (M)</td><td>Typically with unconsolidated layer of flattened siliceous plate scales, which consist of upper and lower plates, connected by internal septae; scales usually surrounded by a hollow margin; organic spicules may occur. <i>Raphidiophrys</i>.</td></tr></tbody></table>

(continued)

<footnote n="39"><sup>39</sup>One more genus name—*Heteroraphidiophrys*, mentioned in Mikrjukov (2002) was never formally introduced and needs to be avoided; the organisms designated needs to be re-isolated, carefully studied and provided with formal description.</footnote>

<footnote n="40"><sup>40</sup>Genera *Pseudoraphidiophrys*, *Pseudoraphidocystis*, *Pterocystis*, *Raineriophrys* altogether obviously unify a group of closely related organisms which need a careful taxonomic revision involving morphological and molecular data. The genus name *Echinocystis* sometimes used instead of *Raineriophrys* is multiply preoccupied and should be avoided.</footnote>

<footnote n="41"><sup>41</sup>For more detailed description of the location and nomenclature of SSU rRNA gene expansions in centrohelids see Shishkin et al., 2018.</footnote>

<footnote n="42"><sup>42</sup>Separation of this genus from *Heterophrys* requires further justification.</footnote>
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●● Pterista Shishkin & Zlatogursky 2018</td><td>Two contrasting types of siliceous scales: tangential inner plate scales usually oval (margin not hollow and inrolled but sometimes thickened) sometimes slightly (rarely markedly) narrower at one end, sometimes slightly indented on one side (rarely slightly on both) but never distinctly bilobed; outer bipartite spine scales typically consisting of leaf-like blade with an axial rib, usually in various degree extended apically as a projecting needle-like point (blunt or pointed, but unbranched) and with lateral wings; spine scale base may be rounded or truncated and may be in the same plane as the blade or somewhat bent away from it (Pterocystis) or markedly extended as a distinct shelf or basal disc (sometimes called basal wing) orthogonal to the main blade (Raineriophrys); species with a pronounced basal wing may have lateral wings that are greatly reduced or absent; siliceous scales may be secondarily missing with or without replacing it with organic spicules.</td></tr><tr><td>●●●●● Oxnerellidae Cavalier-Smith & Chao 2012 (M)</td><td>Naked, without scales, spicules or mucus coat; axopodia either radiating from the centrosome in all directions or appressed to substratum; extrusomes conspicuous. Oxnerella.</td></tr><tr><td>●●●●●● Pterocystidae Cavalier-Smith & von der Heyden 2007</td><td>With two contrasting layers of siliceous scales: inner plate scales and outer bipartite leaf-like spine scales; if siliceous scales secondarily missing (Chlamydaster) cell has a distinct mucous coat. Pterocystis, Raineriophrys, Chlamydaster; Pseudoraphidiophrys; Pseudoraphidocystis.<sup>40</sup></td></tr><tr><td>●●●●●●● Heterophryidae Poche 1913, emend. Cavalier-Smith & von der Heyden 2007</td><td>Lacking siliceous scales but with numerous thin pointed organic spicules tapering towards acute apices; SSU rRNA gene short, lacking expansions in panacanthocystid increase regions<sup>41</sup> (PINs) 1, 2, 6, 7, 9-12, 14 found in Marophryidae. Heterophrys, Sphaerastrum.<sup>42</sup></td></tr><tr><td>●●● Panacanthocystida Shishkin & Zlatogursky 2018</td><td>Usually with siliceous scales or with organic spicules: scale-bearing species with both inner plate scales and outer scales of different morphology or only plate scales with a hollow inrolled margin; outer scales may be of different types based on the plate scale morphology or radially symmetrical spine scales, present in one of two forms: funnel-shaped, or needle-like with a radially symmetrical base. Gene of SSU rRNA usually has at least five expansions in panacanthocystid increase regions (PINs). The most inclusive clade containing Acanthocystis nichollsi, Marophrys marina and Yogsothoth knorrus but not a Pterocystis devonica.</td></tr><tr><td>●●●● Yogsothothidae Shishkin & Zlatogursky 2018 (M)</td><td>Typically with two types of siliceous scales: scales of inner layer are flattened, simple in structure, usually ornamented with axial rib, outer scales may be of different types but more similar to plate, than to spine scales. Gene of SSU rRNA usually having expansions only in panacanthocystid increase regions (PINs) 2, 6, 7, 10, 12. Yogsothoth.</td></tr><tr><td>●●●●● Acanthocystida Cavalier-Smith & von der Heyden 2007 emend. Shishkin & Zlatogursky 2018</td><td>Usually with siliceous scales or with organic spicules: scale-bearing species with both plate and spine scales or only plate scales with a hollow inrolled margin; outer spine scales radially symmetrical, present in one of two forms: funnel-shaped, or needle-like with a radially symmetrical base. Gene of SSU rRNA usually has expansions at least in panacanthocystid increase regions (PINs) 1, 2, 6, 7, 9-12, 14.</td></tr><tr><td>●●●●●●● Marophryidae Cavalier-Smith & von der Heyden 2007 emend. Shishkin & Zlatogursky 2018 (M)</td><td>Without silica scales but covered with numerous thin, pointed organic scales tapering towards acute apices; gene of SSU rRNA usually having expansions only in panacanthocystid increase regions (PINs) 1, 2, 6, 7, 9-12, 14, not found in Heterophryidae. Marophrys.</td></tr><tr><td>●●●●●●●● Chalarothoracina Hertwig & Lesser 1874 sensu Cavalier-Smith in Yabuki et al. 2012 emend. Shishkin & Zlatogursky 2018)</td><td>Usually with siliceous scales or with organic spicules; scale-bearing species with both plate and spine scales or only plate scales with a hollow inrolled margin; outer scales radially symmetrical, present in one of two forms: funnel-shaped, or needle-like with a radially symmetrical base; gene of SSU rRNA usually with expansions at least in panacanthocystid increase regions (PINs) 1-7, 9-12, 14.</td></tr><tr><td>●●●●●●●●● Acanthocystidae Claus 1874 emend. Shishkin & Zlatogursky 2018 (M)</td><td>With two contrasting types of siliceous scales, an inner layer of typically oval plate scales (usually without an inrolled hollow edge) and an outer layer of needle-like spine scales sometimes apically branched and/or with a peltate radially symmetrical basal disc lacking a lateral indentation (unlike Choanocystis spine scales). Acanthocystis.</td></tr><tr><td>●●●●●●●●●● Raphidocystidae Zlatogursky 2018 (M)</td><td>With monolayered plate scales, covering cell surface; plate scales with a hollow inflected margin; sometimes trumpet-shaped or tubular spine scales present, forming an outer layer of coverings; at some life cycle</td></tr></tbody></table>

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>stages the siliceous scales are completely substituted with organic spicules with some intermediate stages having a combination of the siliceous scales and organic spicules. <i>Raphidocystis</i>.</td><td><strong>Cryptista</strong><sup>43</sup> Adl et al. 2019 [Cavalier-Smith 1989, 2018] (R)<br/>This is a node-based definition for the clade stemming from the most recent common ancestor of <i>Cryptomonas</i>, <i>Goniomonas</i>, <i>Kathablepharis</i>, and <i>Palpitomonas</i>. The name does not apply if any of the following fall within the specified clade: <i>Glaucocystis nostochinearum</i>, <i>Chlamydomonas reinhardtii</i>, <i>Telonema subtilis</i>, <i>Emiliana huxleyi</i>.</td></tr><tr><td><strong>●● Palpitomonas Yabuki & Ishida 2010 (M)</strong><br/>Marine isolate, free-living heterotrophic, heterokont biciliate, with unilateral bipartite mastigonemes on anterior cilium; cilia emerge on left side with anterior cilium vigorous and trailing posterior cilium; when swimming, in slow gyromotion; one cilium can adhere to substratum; double-layered MLS-like structure on one ciliary root; vacuolated cytoplasm; phagotrophic on bacteria; without ejectisomes; flat mitochondrial cristae. <i>Palpitomonas bilix</i>.</td><td><strong>Cryptophyceae Pascher 1913</strong>, emend. Schoenichen 1925, emend. Adl et al. 2012 [Cryptophyta Silva 1962; Cryptophyta Cavalier-Smith 1986]<br/>Autotrophic, mixotrophic or heterotrophic with ejectisomes (trichocysts); mitochondrial cristae flat tubules; two cilia emerging subapically or dorsally from right side of an anterior depression (vestibulum); longitudinal grooves (furrows) and/or tubular channels (gulletts) or a combination of both, extending posteriorly from the vestibubulum on the ventral side; gullet/furrow complexes lined with large ejectisomes; with or without plastid nucleomorph complex; chloroplasts when present contain chlorophylls a and c2 and phycobiliproteins, located in thylakoid lumen; chloroplast covering comprised of inner and superficial periplast components (IPC and SPC respectively); includes heterotrophic species formerly known as <i>Chilomonas</i> and some genera diplomorphic such as <i>Cryptomonas</i> and <i>Proteomonas</i>.</td></tr><tr><td><i>Incertae sedis</i> Cryptophyceae: Bjornbergiella.</td><td><strong>Cryptomonadales Pascher 1913</strong><br/>Chloroplasts or leucoplasts present. <i>Chroomonas</i>, <i>Cryptomonas</i>, <i>Falcomonas</i>, <i>Geminigera</i>, <i>Guillardia</i>, <i>Hanusia</i>, <i>Hemiselmis</i>, <i>Plagioselmis</i>, <i>Proteomonas</i>, <i>Rhinomonas</i>, <i>Rhodomonas</i>, <i>Storeatula</i>, <i>Teleaulax</i>.</td></tr><tr><td><strong>●●● Cyathomonadacea Pringsheim 1944</strong><br/>Chloroplasts absent. <i>Goniomonas</i> (previously <i>Cyathomonas</i>), <i>Hemiarma</i>.</td><td><strong>Cyathablepharidacea Skuja 1939</strong> [Kathablepharidae Vørs 1992]<br/>Free-swimming cells with two heterodynamic cilia inserting subapically/medially; cell membrane thickened by lamellar sheath; ingest eukaryotic prey through an apical cytostome supported by bands of longitudinal microtubules; extrusomes are large coiled-ribbons arrayed near kinetosomes; tubular mitochondrial cristae; plastids not observed. <i>Hatena</i>, <i>Kathablepharis</i>, <i>Leucocryptos</i>, <i>Platychilomonas</i>, <i>Roombia</i>.</td></tr><tr><td><strong>Incertae sedis</strong> EUKARYA<br/><strong>EXCAVATES</strong> [Excavata Cavalier-Smith 2002, emend. Simpson 2003] (P)<br/>Typically with suspension-feeding groove of the "excavate" type, secondarily lost in many taxa; feeding groove used for capture and ingestion of small particles from feeding current generated by a posteriorly directed cilium (F1); right margin and floor of groove are supported by parts of the R2 microtubular root, usually also supported by microtubular fibres (B fibre, composite fibre), and the left margin by the R1 microtubular root and C fibre. Grouping of Metamonada and Discoba and Malawimonads is somewhat controversial, although recent multigene phylogenies have markedly increased support for monophyly of Metamonada, and of Discoba, separately. Apomorphy: Suspension-feeding groove, homologous to that in *Jakoba libera*. Recent phylogenies indicate Metamonada and Dicoba probably do not share the same node.</td><td><strong>Metamonada Grassé 1952</strong>, emend. Cavalier-Smith 1987<br/>Anaerobic/microaerophilic, either with modified mitochondria that lack cristae, are nonrespiratory, and lack a genome (e.g. hydrogenosomes or mitosomes), or without mitochondria; mostly ciliated cells, ancestrally with four kinetosomes per kinetid, though a great variation exists; some free-living, many endobiotic, some parasitic. Apomorphies: mitochondrial organelles anaerobic and non-respiratory (secondarily lost in oxymonads); four kinetosomes per kinetid (secondarily modified in a number of lineages).</td></tr><tr><td><i>Incertae sedis</i> Metamonada: Barthelona</td><td></td></tr></tbody></table>

(continued)

<footnote n="43">⁴³Cryptista has been used since 1989 with a variety of definitions, and varying in composition and rank. Unless the authority and date is specified, it is uncertain which meaning, or rank, of Cryptista is meant. However, the term has uses in phylogenetic trees and it has been somewhat adopted in the literature, although without precision over its meaning. For nomenclatural stability Cryptista is defined here according to its latest use in phylogenetic trees.</footnote>
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●● Fornicata Simpson 2003</td><td>With a single kinetid and nucleus, or a pair of kinetids and nuclei; 2-4 kinetosomes and 1-4 cilia per kinetid; usually with a feeding groove or cytopharyngeal tube associated with each kinetid. Nonrespiratory mitochondria without cristae. Apomorphy: "B fibre" originates against R2 microtubular root (secondarily lost in Diplomonadida and Caviomonadidae).</td></tr><tr><td>●●● "Carpediemonas-like organisms" (Kolisko et al. 2010) (P)</td><td>Free-living, marine, anaerobic/microaerophilic ciliated cells with a broad ventral suspension-feeding groove; biciliated, but with 2-4 kinetosomes; posterior cilium with 1-3 vanes and beating within the groove; with relatively large cristae-lacking mitochondria; paraphyletic assemblage within Fornicata in molecular phylogenies. Aduncisulcus, Carpediemonas, Dystenectes, Ergobibamus, Hicanonectes, Kipferlia.</td></tr><tr><td>●●●● Diplomonadida Wenyon 1926</td><td>Usually with 'diplomonad' cell organization, namely a pair of kinetids and two nuclei; some taxa ('enteromonads') have a single kinetid and nucleus, probably secondarily; each kinetid usually with four ciliated kinetosomes but sometimes only two or three ciliated; at least one cilium per kinetid directed posteriorly, associated with a cytopharyngeal tube or groove, or stretching as free axoneme axially within the cell; various nonmicrotubular fibres supporting the nucleus and cytopharyngeal apparatus; free-living or endobiotic, often parasitic. Apomorphy: diplomonad cell organization.</td></tr><tr><td>●●●●● Hexamitinae Kent 1880</td><td>With cytopharyngeal tube or groove; with an alternate genetic code—TAR codons for glutamine; several have a single kinetid and nucleus; endobiotic or secondarily free-living. Enteromonas, Gyromonas*, Hexamita, Spironucleus, Trepomonas, Trigonomonas*, Trimitus.</td></tr><tr><td>●●●●●● Giardiinae Kulda & Nohýnková 1978</td><td>Without distinct feeding apparatus; one posteriorly directed cilium from each kinetid (F1) runs through the length of the cell axially and is intracytoplasmic; with standard genetic code; all endobiotic and with 'diplomonad' cell organization. Brugerolleia*, Giardia, Octomitus.</td></tr><tr><td>●●●● Retortamonadida Grassé 1952 (P)</td><td>Single ciliary apparatus with four kinetosomes and either two (Retortamonas) or four (Chilomastix) emergent cilia; posterior cilium has 2-3 vanes and is associated with a ventral feeding groove with posterior cytostome; cell surface often underlain by a corset of microtubules; all endobiotic, except for one free-living species. Apomorphy: "lapel" structure as an electron-dense sheet supporting the anterior origin of the peripheral microtubules. Chilomastix, Retortamonas. Note that molecular phylogenetic studies currently do not support monophyly, perhaps due to misidentification/polyphyly of Retortamonas spp.</td></tr><tr><td>●●●● Caviomonadidae Cavalier-Smith 2013</td><td>Single ciliary apparatus with two or four kinetosomes and a single cilium without vanes; ventral groove rudimentary or lost; microtubular cytoskelet simple, consisting from nuclear fibre and dorsal fan; endobiotic or free-living. Caviomonas*, lotanema.</td></tr><tr><td>●● Parabasalia Honigberg 1973</td><td>Cells with a parabasal apparatus—two or more striated parabasal fibres connecting the Golgi apparatus to the ciliary apparatus; kinetid ancestrally with four cilia/kinetosomes, but frequently with additional cilia (one to thousands); one kinetosome bears sigmoid fibres that connect to a pelta-axostyle complex; reduction or loss of the ciliary apparatus in some taxa, multiplication of complete or parts of the ciliary apparatus in other taxa; closed mitosis with an external spindle, including a conspicuous microtubular bundle; mitochondria transformed to acristate hydrogenosomes; mostly endobiotic, some parasitic, some free-living, presumably secondarily. Apomorphy: parabasal apparatus.</td></tr><tr><td>Incertae sedis Parabasalia: Tricercomitus.</td><td></td></tr><tr><td>●●● Trichomonadida Kirby 1947</td><td>Four to six (four ancestrally) cilia with one ciliary axoneme supporting a lamelliform undulating membrane; B-type costa, sometimes absent; comb-like structure and infrakinetosomal body absent; axostyle usually of "Trichomonas type"; mostly endobiotic, some parasitic, exceptionally free-living. Cochlosoma, Dientamoeba, Lacusteria, Pentatrichomonas, Pentatrichomonoides, Pseudotrichomonas, Pseudotrypanosoma, Tetratrichomonas, Trichomonas, Trichomonoides, Trichomitopsis.</td></tr><tr><td>●●●● Honigbergiellida Čepička et al. 2010 (P?)</td><td>Two and more than 20 (four ancestrally) cilia with one ciliary axoneme sometimes supporting a lamelliform undulating membrane; costa, comb-like structure, and infrakinetosomal body absent; axostyle usually of "Trichomonas type", sometimes of "Tritrichomonas type"; usually free-living, some endobiotic. Ditrichomonas, Cthulhu, Cthylla, Hexamastix, Honigbergiella, Monotrichomonas.</td></tr></tbody></table>

(continued)
<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>
  <tbody>
    <tr>
      <td>●●● Hypotrichomonadida Čepička et al. 2010</td>
    </tr>
    <tr>
      <td>Four cilia with one ciliary axoneme supporting a lamelliform undulating membrane; A-type costa, sometimes absent; comb-like structure present, but no infrakinetosomal body; biramous parabasal body; axostyle usually of "Trichomonas type"; endobiotic. Hypotrichomonas, Trichomitus.</td>
    </tr>
    <tr>
      <td>●●● Tritrichomonadida Čepička et al. 2010 (P?)</td>
    </tr>
    <tr>
      <td>Uninucleate or binucleate; 0–5 (four ancestrally) cilia; ancestrally with comb-like structure, suprakinetosomal and infrakinetosomal body; if present, undulating membrane typically of rail type, sometimes lamelliform; A-type costa, often absent; axostyle of "Tritrichomonas type" or "Trichomonas type"; endobiotic, some parasitic. Dientamoeba, Histomonas, Monocercomonas, Parahistomonas, Simplicimonas, Tritrichomonas.</td>
    </tr>
    <tr>
      <td>●●● Cristamonadida Brugerolle &amp; Patterson 2001</td>
    </tr>
    <tr>
      <td>Uninucleate to multinucleate; akaryomastigonts in addition to karyomastigonts in some multinucleate genera; four-to-thousands of cilia per mastigont; kinetosomes, except for 'privileged kinetosomes', often discarded during cell division in highly ciliated taxa; some with cresta and paraxonemal rod associated with the recurrent cilium; axostyle ancestrally of "Tritrichomonas type", secondarily thin or reduced in some; multiple axostyles in multinuclear forms; parabasal body single or multiple, ellipsoid or rod-shaped, often spiralled or ramified; endobiotic. Caduceia, Calonympha, Coronympha, Deltotrichonympha, Devescovina, Foaina, Gigatomonas, Joenia, Joenina, Joenoides, Joenopsis*, Kofoidia, Koruga, Macrotrichomonas, Macrotrichomonoides, Metadevescovina, Mixotricha, Pachyjoenia*, Projoenia*, Pseudodevescovina, Rhizonympha*, Snyderella, Stephanonympha.</td>
    </tr>
    <tr>
      <td>●●● Spirotrichonymphida Grassé 1952</td>
    </tr>
    <tr>
      <td>Multiple kinetosomes in counterclockwise spiral rows; cilia retained during cell division with the ciliary rows dividing between daughter cells; axostyle single of "Tritrichomonas type", or multiple in thin bands, or reduced; endobiotic. Holomastigotes*, Holomastigotoides, Microjoenia*, Micromastigotes*, Rostronympha*, Spiromastigotes*, Spironympha*, Spirotrichonympha*, Spirotrichonymphella, Uteronympha*.</td>
    </tr>
    <tr>
      <td>●●● Lophomonadida Light 1927</td>
    </tr>
    <tr>
      <td>Multiple kinetosomes in a single kinetid arranged in an ear-shaped row partially encircling the nucleus; single thin axostyle; endobiotic. Lophomonas.</td>
    </tr>
    <tr>
      <td>●●● Trichonymphida Poche 1913</td>
    </tr>
    <tr>
      <td>Bilaterally or tetraradially symmetrical, with anterior rostrum divided into two hemirostra; each hemirostrum bears one or two ciliary areas with hundreds to thousands of cilia; cilia usually retained during cell division; one hemirostrum goes to each daughter cell; numerous parabasal fibres originate from two or four parabasal plates that form a rostral tube in some; numerous thin axostyles do not protrude outside the cell; endobiotic. Barbulanympha, Eucomonympha, Heliconympha, Hoplonympha, Leptospionympha, Macrospironympha*, Pseudotrichonympha, Rhynchonympha*, Spirotrichomonas*, Staurojoenina, Teranympha, Trichonympha, Urinympha.</td>
    </tr>
    <tr>
      <td>●● Preaxostyla Simpson 2003</td>
    </tr>
    <tr>
      <td>Heterotrophic cell with four cilia and kinetosomes per kinetid; nonrespiratory mitochondria without cristae or absent. Apomorphy: "I fibre" associated with R2 root has 'preaxostylar' substructure—latticework paracrystalline layer of 'double-cross' thickness with a single, fine outer layer.</td>
    </tr>
    <tr>
      <td>●●● Oxymonadida Grassé 1952</td>
    </tr>
    <tr>
      <td>Single kinetid (occasionally multiple kinetids) consisting of two pairs of ciliated kinetosomes distantly separated by a preaxostyle (microtubular root R2 and paracrystalline I fibre), from which arises a microtubular axostyle; axostyle consists of parallel rows of microtubules and is contractile in some taxa; microtubular pelta present in some genera; mitochondrion either absent or non-recognized, gut endosymbionts, mostly in lower termites and *Cryptocercus*, many taxa attach to gut wall using an anterior holdfast; closed mitosis with internal spindle. Apomorphy: Absence of ventral groove. Kinetosomes grouped in two pairs. Axostyle formed by parallel rows of microtubules, (not homologous to that of Parabasalia). Absence of recognizable mitochondrion. Barroella, Blattomonas, Brachymonas, Dinenympha, Microrhopalodina, Monocercomonoides, Notila, Opisthomitus, Oxymonas, Paranotila, Polymastix, Pyrsonympha, Sauromonas, Saccinobaculus, Streblomastix, Tubulimonoides.</td>
    </tr>
    <tr>
      <td>●●● Trimastigidae Saville Kent 1880-1882</td>
    </tr>
    <tr>
      <td>Free-living excavate cells bearing four cilia stretched roughly in the anterior, right, left, and posterior directions; a broad ventral feeding groove, in which beats the posteriorly directed cilium; posterior cilium with two broad vanes without thickened vane margins, no conspicuous lateral cytopharynx; nonrespiratory mitochondria without cristae. Marine and freshwater. Trimastix.</td>
    </tr>
  </tbody>
</table>

(continued)
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●● Paratrimastigidae Zhang et al. 2015

Similar to Trimastigidae but with thickened vane margins on posterior cilium; lateral cytopharynx may be present; freshwater species only. *Paratrimastix*.

● **Discoba** Simpson in Hampl et al. 2009 (R)

A grouping robustly recovered in multigene phylogenetic analyses, containing Heterolobosea, Euglenozoa, Jakobida, and Tsukubamonadida; ancestrally biciliate. Node-based definition: the clade stemming from the most recent common ancestor of *Jakoba libera*, *Andalucia godoyi*, *Euglena gracilis*, *Naegleria gruberi* and *Tsukubamonas globosa*.

●● Jakobida Cavalier-Smith 1993

With two cilia at the head of a broad ventral feeding groove, in which beats the posterior cilium; posterior cilium with a single dorsal vane that is distinctive among excavates but possibly plesiomorphic; free-living.

●●● Andalucina Cavalier-Smith 2013

Free-swimming cells, attaching temporarily to surfaces; aerobic with tubular mitochondrial cristae or anaerobic with acristate mitochondria. With a G:C base pair within the base of the stem of "helix 27" of the 18S rRNA molecule (positions 1050 and 1085 in the *Andalucia incarcerata* 18S rRNA gene sequence AY117419).

●●●● Andaluciidae Cavalier-Smith 2013

Aerobic, mitochondria cristate. *Andalucia*.

●●●●● Stygiellidae Pánek et al. 2016

Anaerobic, mitochondria acristate. *Stygiella*, *Velundella*.

●●● Histonina Cavalier-Smith 2013

Free-swimming or sessile cells, some genera with lorica; aerobes with flat mitochondrial cristae. Without the Andalucina-specific G:C base pair within the base of the stem of "helix 27" of the 18S rRNA molecule. *Histonia*, *Jakoba*, *Moraemonas*, *Reclinomonas*, *Seculamonas* nomen nudum.

●● Tsukubamonadida Yabuki et al. 2011 (M)

Rounded biciliate cell, with four kinetosomes per kinetid; aerobic; consumes prey through ventral groove; dyctosomes and ciliary vanes absent. *Tsukubamonas*.

●● Heterolobosea Page & Blanton 1985

Typically with ciliated and amoeboid phases, though many species lack the ciliated phase, while some others lack the amoeboid phase; rarely amoeboid when ciliated; amoebae often with eruptive pseudopodia; ciliated cells usually with two or four cilia (rarely uni- or multiciliate), sometimes nonfeeding; if capable of feeding usually use a groove-like cytotome; closed mitosis with internal spindle; mitochondrial cristae flattened, often discoidal, mitochondria sometimes acristate; discrete dyctosomes not observed; ciliary vanes usually absent. Apomorphy: complex life cycle containing amoeba, ciliate and cyst.

●●● Pharyngomonada Cavalier-Smith 2008

Amoebae usually flabellate or ovoid, eruptive movement rare; with four cilia in side-by-side obtuse pairs; feeding using a large groove and cytopharynx; with amoeboid phase; lack helix 17-1 region in SSU rRNA that is typical of Tetramitia. *Pharyngomonas*.

●●●● Tetramitia Cavalier-Smith 1993

Amoebae usually with cylindrical, eruptive pseudopodia; swimming form usually with four cilia or two per kinetid. Apomorphy: distinct helix 17-1 in the SSU rRNA molecule.

●●●●● Selenaionidae Hanousková et al. 2018

Amoeboid or ciliated; when present with two cilia per kinetid, with orthogonally arranged kinetosomes; finger-like projection on the proximal part of the recurrent cilium; nucleus with parietal nucleoli. *Dactylomonas*, *Selenaion*.

●●●●●● Neovahlkampfiidae Hanousková et al. 2018

Amoebae; nucleus with central nucleolus. *Neovahlkampfia*.

●●●●●● Eutetramitia Hanousková et al. 2018

Amoebae or ciliated; when present usually with four cilia or two per kinetid, with parallel kinetosomes, although *Stephanopogon* has numerous monokinetids, *Creneis* has up to 14 cilia emerging from two to three places; nucleus with central or parietal nucleoli.

●●●●●●● Vahlkampfiidae Jollos 1917 (P)

Ciliated amoebae or amoeboid without cilium; quadriciliate or biciliate; nucleolus persists through mitosis; single nucleus *Fumarolamoeba*, *Heteramoeba*, *Naegleria*, *Neovahlkampfia*, *Paravahlkampfia*, *Tetramitus*, *Vahlkampfia*, *Willaertia*.

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<table><caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption><thead><tr><th></th><th></th></tr></thead><tbody><tr><td>●●●●● Gruberellidae Page & Blanton 1985</td><td>Locomotion amoeboid or swimming with cilia; nucleolus fragments during mitosis; uninucleate or multinucleate; ciliated form observed in unidentified species of Stachyamoeba. Gruberella*, Stachyamoeba.</td></tr><tr><td>●●●●● Acrasidae Poche 1913</td><td>Amoebae of some species aggregate to form fruiting bodies; nucleus may or may not fragment. Apomorphy: Formation of fruiting bodies. Acrasis, Allovahlkampfia, Pocheina.</td></tr><tr><td>●●●●● Percolomonadidae Cavalier-Smith 2008</td><td>Swimming cells with four cilia; without amoeboid from; aerobic. Percolomonas.</td></tr><tr><td>●●●●● Psalteriomonadidae Cavalier-Smith 1993</td><td>Cell amoeboid with or without cilia, or swimming with one cilium; when amoeboid and ciliated, with 4 groups of 4 cilia; anaerobic. Harpagon, Psalteriomonas, Monopylocystis, Pseudoharpagon, Sawyeria.</td></tr><tr><td>●●●●● Stephanopogonidae Corliss 1961</td><td>Always with multiple cilia; aerobic. Stephanopogon.</td></tr><tr><td>●●●●● Crenidae Pánek et al. 2014 (M)</td><td>Amoeboid with a single cilium or multiciliate; anaerobic with acristate mitochondria. Creneis.</td></tr><tr><td>●●●●● Tulamoebidae Kirby et al. 2015</td><td>Biciliate, locomotion amoeboid or swimming with cilia; with elongate ingestion apparatus opening slightly posterior to the ciliary insertion; halophilic or very halotolerant. Pleurostomum, Tulamoeba.</td></tr><tr><td>●● Euglenozoa Cavalier-Smith 1981, emend. Simpson 1997</td><td>Cells with two cilia, occasionally one, rarely more, inserted into an apical/subapical ciliary pocket; with rare exceptions, emergent cilia with heteromorphic paraxonemal rods; usually with tubular feeding apparatus associated with ciliary apparatus; basic ciliary apparatus pattern consisting of two functional kinetosomes and three asymmetrically arranged microtubular roots; single mitochondrion mostly with discoidal cristae. Apomorphy: heteromorphic paraxonemal rods, tubular/whorled in anterior cilium F2 and a parallel lattice in posterior cilium F1.</td></tr><tr><td>●●● Euglenida Butschli 1884, emend. Simpson 1997</td><td>With a pellicle of proteinaceous strips, fused in some taxa; when unfused and with > ~20 strips capable of active distortion (metabolty); where known, paramylon is the carbohydrate store. Apomorphy: Pellicle of protein strips.</td></tr><tr><td>●●●●● Heteronematina Leedale 1967 (P)<sup>44</sup></td><td>With ingestion apparatus capable of phagotrophy; lacking plastids; most glide on surfaces on one or both cilia; a para-phyletic assemblage from which Euglenophyceae and Aphagea are descended. Anisonema, Atraktomonas, Biundula, Calycimonas, Decastava, Dolium, Cinema, Dylakosoma, Entosiphon, Heteronema, Jenningsia, Keelungia, Lentomonas, Neometanema, Notosolenus, Pentamonas, Peranema, Peranemopsis, Petalomonas, Ploeotia, Scytomonas, Ser-penomonas, Sphenomonas, Teloprocta, Tropidoscyphus, Urceolus.</td></tr><tr><td>●●●●● Aphagea Cavalier-Smith 1993, emend. Busse & Preisfeld 2002</td><td>Osmotrophic euglenids lacking photosensory apparatus and plastids; one or two emergent cilia; no ingestion apparatus. Astasia s.s., Distigma, Gyropaigne, Menoidium, Parmidium, Rhabdomonas.</td></tr><tr><td>●●●●● Euglenophyceae Schoenichen 1925, emend. Marin & Melkonian 2003 [Euglenea Butschli 1884, emend. Busse and Preisfeld 2002]</td><td>Phototrophic, with one to several plastids of secondary origin with three bounding membranes and chlorophylls a and b; some species secondarily non-photosynthetic; most with extraplastidic eyespot and photosensory apparatus associated with cilia; most motile.</td></tr><tr><td>●●●●● Rapaza Yamaguchi et al. 2012</td><td>Cells solitary, cytotrophic on microalgae with two heterodynamic cilia of unequal length; pellicle with helically arranged strips capable of metaboly locomotion; discoidal chloroplast(s) with pyrenoids surrounded by three membranes; marine species. Rapaza.</td></tr></tbody></table>

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<footnote n="44">⁴⁴Presently, there is no phylogenetic taxonomy for phagotrophic euglenids as a whole. Traditional systems based on, for example, the presence or absence of conspicuous feeding apparatuses, are artificial. Some possibly monophyletic taxa have been proposed that would cover restricted subsets of the phagotrophic euglenids: for example, the Ploeotiida, including Ploeotia, Entosiphon, Lentomonas, and presumably Keelungia; and the Petalomonadida, including Petalomonas, Notosolenus and Calycimonas, and presumably also taxa such as Sphenomonas. The limited taxon sampling for molecular sequence data is a significant impediment, especially as many traditional genera are probably polyphyletic.</footnote>
<caption>**Table 2** Classification of the higher ranks of the protists and multicellular organisms.</caption>

●●●●● Eutreptiales Leedale 1967, emend. Marin & Melkonian 2003
2-4 emergent heterodynamic cilia of equal or unequal length; cells not rigid, usually capable of metaboly; mostly marine or brackish species, rarely freshwater. *Eutreptia, Eutreptiella*.

●●●●● Euglenales Leedale 1967, emend. Marin & Melkonian 2003
Single emergent cilium and second cilium within the reservoir, or both cilia non-emergent; phototrophic or secondly heterotrophic; mostly freshwater species.

●●●●●● Phacaceae Kim et al. 2010
Solitary, with one emergent cilium; palmelloid stages, cysts and envelopes unknown; numerous small discoid chloroplasts without pyrenoids, large paramylon grains. *Discoplastis, Lepocinclis, Phacus*.

●●●●●● Euglenaceae Dujardin 1841, emend. Kim et al. 2010.
Cells solitary or colonial, with one emergent cilium; some with palmelloid stages, especially in *Euglena*; *Strombomonas* and *Trachelomonas* loricate; one large to several small chloroplasts of various shapes with or without pyrenoid. *Ascoglena, Colacium, Cryptoglena, Euglena, Euglenaformis, Euglenamorpha, Euglenaria, Euglenopsis, Hegneria, Klebsina, Monomorphina, Strombomonas, Trachelomonas*.

●●● Diplonemea Cavalier-Smith 1993, emend. Simpson 1997
Heterotrophic cells exhibiting pronounced metaboly; both cilia are short and usually supported with paraciliary rod; apical papilla, feeding apparatus with 'pseudovanes'; few giant, flattened mitochondrial cristae.

●●●● Diplonemidae Cavalier-Smith 1993, emend. Adl et al. 2019
Perform extensive *trans*-splicing and editing of mitochondrial RNA; trophic stage present; some species contain endosymbiotic bacteria; metaboly always present. *Diplonema, Rhynchopus, Lacrimia, Sulcionema, Flectonema*.

●●●●● Hemistasiidae Cavalier-Smith 2016, emend. Adl et al. 2019
Anterior rostrum; large posterior vacuole; contain numerous extrusomes; *Hemistasia*.

●●●● Eupelagonemidae Okamoto & Keeling 2018.
Previously refered to as the deep-sea pelagic diplonemids (DSPD1 clade). Possible lack of metaboly, represent ~97% of all marine diplonemids, globally distributed. *Eupelagonema*.

●●● Symbiontida Yubuki et al. 2009
Microaerobic or anaerobic cells that possess rod-shaped epibiotic bacteria; lack euglenid type pellicle strips. Currently treated as a major taxon within Euglenozoa, but are probably derived phagotrophic euglenids. Apomorphy: Rod-shaped epibiotic bacteria above superficial layer of mitochondrion-derived organelles with reduced or absent cristae, homologous to the organization in *Calkinisia aureus*. *Bihospites, Calkinsia, Postgaardi*.

●●● Kinetoplastea Honigberg 1963
Cells with a kinetoplast, which is a large mass(es) of mitochondrial (=kinetoplast; k) DNA; Apomorphy: kinetoplast; mitochondrial RNA editing; *trans*-splicing of splice leader RNA; polycistronic transcription.

*Incertae sedis* Kinetoplastea: *Bordnamonas, Cephalothamnium, Rhynchoidomonas*.

●●●● Prokinetoplastina Vickerman in Moreira et al. 2004 (R)
Two genera: *Ichthyobodo* are polykinetoplastic and biciliated cells with the cilia originating in a pocket that continues as a furrow; ectoparasitic, freshwater, and marine. *Perkinsela*-like organisms (PLOs), oval cells with a single large kinetoplast, non-ciliated, live as endosymbionts ('parasomes') of certain amoebae (e.g. *Paramoeba* spp.), but are not enclosed in parasitophorous membrane. *Ichthyobodo, Perkinsela*.

●●●●● Metakinetoplastina Vickerman in Moreira et al. 2004 (R)
Group identified by SSU rRNA phylogenies. Node-based definition: clade stemming from the most recent common ancestor of Neobodonida, Parabodonida, Eubodonida, and Trypanosomatida.

●●●●●● Neobodonida Vickerman in Moreira et al. 2004 (R)
Eu- or polykinetoplastic kDNA not in a single network, but in multiple loci throughout the mitochondrion; biciliated, without conspicuous hairs; posterior cilium attached or free; phagotrophic or osmotrophic; preciliary rostrum containing apical cytosome. Node: *Actuariola, Azumiobodo, Cruzella, Cryptaulax, Dimastigella, Klosteria, Neobodo, Phanerobia, Rhynchobodo, Rhynchomonas*.

●●●●●● Parabodonida Vickerman in Moreira et al. 2004 (R)
Pankinetoplastic kDNA not in a single network, but evenly distributed in the mitochondrion; biciliated, without

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